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Extension > Yard and Garden News > 2009

Tuesday, December 1, 2009

Cool Plants for the Holidays

Carl Hoffman, University of Minnesota Extension Horticulturist

Be it reasons relating to the economy, an elevated environmental consciousness, or merely a reason to wear a new Snuggie™, we are lowering the temperature in our homes. We can easily compensate for the cool temperatures, but what about our plants?

As we enter the holiday season, many of us plant lovers like to use blooming plants to brighten and add seasonal cheer to the interior of our homes. Nearly all of the holiday favorites will perform well for a while, but then will begin to languish.

We are fortunate, however, that there are some blooming holiday plants that actually thrive in cool, or even cold, temperatures. Generally, temperatures above freezing, but below 50° F are considered cold, and temperatures between 50° F and 65° F are considered cool. Even some plants, like the poinsettia that prefer warmer temperatures will do quite well in a cooler environment if they are kept from cold drafts and are not overwatered.

Cyclamens

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A bench full of solid and bicolor Cyclamens
Carl Hoffman
There are not many of us that keep our homes below 50° F, but if we did, cyclamens would be happy. The florist cyclamen, Cyclamen persicum, prefers night temperatures of 40° to 50° F and daytime temperatures below 65° F. These plants, with their large backswept petals in colors ranging from pastel pinks and lilacs to deep red and snow white, make beautiful, showy accent plants. The flowers are borne on upright stems that extend above attractive heart-shaped, silver mottled leaves. To prolong the blooming period, select a plant that has only a few flowers open, but many buds.

Cyclamens grow from tubers. They will rot easily if improperly watered so they should be watered from the bottom or, when watered from the top, use care to keep water from the crown of the plant. Allow the surface of the soil to dry slightly before you water, but do not wait until the plant begins to wilt. If placed in a room with cold to cool temperatures, bright light and when watered properly, cyclamen plants can be expected to remain attractive for up to two months.

Azaleas

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Azaleas in perfect bloom stage for bringing home
Carl Hoffman

Indoor azaleas (Rhododendron sp) with their masses of double or semi-double flowers in colors including white, pinks, salmons, reds and bicolors make a commanding holiday accent. With optimum temperatures of 45° to 55° F at night and up to 68° F during the day, azaleas will remain attractive for a month or more. When selecting an azalea plant for your home, do not be tempted to purchase a beauty in full bloom, but rather one that has a few flowers open and color showing in most of the buds. Azaleas need to be kept constantly moist and should be watered thoroughly whenever the soil in the pot feels dry to the touch. Azalea plants will drop their leaves if allowed to get too dry or if they are placed in a room with low humidity. For maximum performance, place your azalea where it receives at least four hours of bright, indirect light each day. An indoor azalea in full bloom is truly a living bouquet.

Orchids


Orchids immediately bring to mind the tropics and warm temperatures, and thus are often overlooked when we are looking for cool temperature plants. However, orchids are an extremely diverse group of plants and there are representatives that will fit nearly every indoor condition, including cool temperatures. Once considered humid greenhouse plants that were difficult to grow under home conditions, there are species that actually require less care than some of our more common indoor plants. Improved breeding techniques have increased their availability and lowered their cost so that we can now readily enjoy these exquisite, long lasting flowers in our homes.

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Paphiopedilum Satin Smoke
Jayme Hennek, Stearns County Master Gardener

There are at least seven genera of orchids that are classified as cool temperature orchids. Of these, I suggest that you try a Cymbidium or Pahiopedilum orchid for the holidays. A Cymbidium orchid plant in bloom with a huge spray of beautiful waxy flowers will make an outstanding accent or gift. There are both standard and miniature forms of Cymbidiums. Their narrow leaved foliage and large sprays of flowers need room, making the miniatures a better fit in most homes. Paphiopedilum or lady slipper orchids are terrestrial orchids and require less light than many of the other orchids. There are two main groups of Paphiopedilums: those with variegated or mottled leaves which require warmer temperatures, and those with green leaves which require cool growing conditions. Their beautiful flowers with their distinctive pouches may last two months or more under good conditions. Because Paphiopedilums grow naturally on the forest floor, they require a potting medium that contains some peat moss with the bark, and less light than do the Cymbidiums.

Christmas cactus

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Christmas cactus in full bud
Carl Hoffman

The Christmas cactus (Schlumbergia) is a beautiful plant that enjoys bright indirect light and cool temperatures, particularly when in bloom. Warm temperatures or drafts will cause the flowers and buds to drop prematurely. Purchase a plant that has many buds that are showing color and then place it where it receives bright light without high temperatures. Purchasing a Christmas cactus can be a long time investment as I have seen specimens that have been in families for 30 years or more. Hybrids have been developed that produce flowers in colors ranging from red, pink, magenta, white and even yellow. They are not true cacti, but are epiphytes similar to many bromeliads and orchids. The soil should be kept moist, but allowed to dry slightly between waterings.

Christmas cactus plants can be frustrating because the flowering period is affected by both day length and temperatures and it may be difficult to get them to bloom during the holidays. To initiate flowering, they require short days of less than 12 hours of light and temperatures of less than 68° F. At temperatures of less than 55° F, the buds will form regardless of day length. If your room only drops to 60° or 65° at night, you need to cover the cactus or put it in a dark closet for at least 12 hours each night to trigger blooming. Unfortunately, a plant grown at temperatures above 70° F probably will not flower regardless of the day length.

Norfolk Island Pine


As I was walking through a favorite greenhouse, I decided that I would be remiss if I did not include a non-blooming plant, the Norfolk Island Pine (Araucaria), on my list of cool temperature holiday plants. This conifer with its whorls of flat branches covered with short, dark green needles can be an accent plant even may even serve as a replacement for the family Christmas tree.

Norfolk Island Pine can be a beautiful focal plant in your home if you have a place where it receives bright light for at least part of the day. They will tolerate lower light for a while, but if not returned to bright light, the branches will droop and the new growth will be weak and pale colored. The most common problems Norfolk Island Pine face indoors are browning needles and dropping lower branches. Usually they can be attributed to hot dry air, low humidity, or allowing the soil to dry excessively before watering. Too much fertilizer can also contribute to needle drop and branch loss. It can be difficult to control the humidity in the home, but careful watering will help compensate for low humidity. Keep the soil moist, but not saturated, and water the plant whenever the soil surface feels dry. Like many of our indoor plants, the lower light intensity and the cooler temperatures of winter make it imperative that these plants are not overwatered.

We can readily see that a home with cool room temperatures need not be a home without blooming plants during the holidays. Well known favorites like cyclamens, azaleas and the long time favorite Christmas cactus welcome the cooler temperatures as do some of the newcomers like orchids. Of course, we can always add the "enjoy and toss" plants like poinsettias, hydrangeas and mums for more temporary bursts of color.

For more information on growing these or any other indoor plants go to http://www.extension.umn.edu/gardeninginfo/

Falling Leaves Reveal Unsightly and Mysterious Galls

Michelle Grabowski, University of Minnesota Extension Educator

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Maple tree infected with many Phomopsis galls
M. Grabowski

As leaves are lost this fall, some gardeners are noticing unsightly lumps and bumps on the bare branches of their trees. A variety of causes, both living and non living, can result in irregular tree growth. However if round rough balls of wood are clustered on the trunk, branches, and twigs of the tree this is likely phomopsis gall. Phomopsis gall is a fungal disease caused by several species of Phomopsis. In Minnesota, Phomopsis galls are most commonly seen on Hickory (Carya spp.) and Maple (Acer spp.) trees. This disease can also infect American elm (Ulmus americana), several species of oak (Quercus spp.), Viburnum spp., Forsythia sp., rhododendrons and azaleas (Rhododendron spp.).

Phomopsis galls are spherical wood balls growing on tree trunks or branches. Galls may be as small as a pea or up to 10 inches in diameter. In most trees, the galls look like a cluster of small nodules or bumps, all pushed together into one lump like a popcorn ball. In maple trees, however, galls often start as smooth round balls and become rough with age as the bark cracks. In all cases, the galls are made of hard disorganized wood that may be difficult to cut through. Examination of young growing gall tissue under a microscope reveals strands of fungal mycelia growing within the wood, but signs of the fungal pathogen are rarely visible to the naked eye.

It is common for a tree to have many galls scattered throughout the branches. Galls may occur individually on branches or be clustered together in small groups. Often one or a few trees in an area will be heavily infected with phomopsis galls and nearby neighbors of the same species will be completely healthy and gall free. Heavily infected trees may have slower growth than their uninfected neighbors. Small twigs that are girdled by one or more galls can be killed. Typically however trees with phomopsis galls are able to continue to grow despite their unusual appearance.

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Phomopsis galls on maple
M. Grabowski

Phomopsis gall is a mysterious disease because very little is known about its lifecycle. Spore producing structures of the fungus are almost never seen on galls. As a result, it is unknown how the fungus spreads from one tree to another and under what conditions infection occurs. No one knows why some trees are highly susceptible to this disease while a neighboring tree of the same species seems to be completely disease free. As a result of this gap in knowledge, few control strategies are available to manage Phomopsis galls. In most cases gardeners are encouraged to tolerate the galls; although heavily infected branches can be pruned off and disposed of. Reducing other stresses on infected trees by mulching the soil around the tree with woodchips or other organic matter, providing water during times of drought, and avoiding accidentally wounding the tree will help the tree to continue to grow at the best rate possible.

An Un-Ordinary Growing Season for All-American Selections at the MN Landscape Arboretum

Redistributed with permission from Arboretum News, Dec./Jan. issue
Ted Pew, Landscape Gardener, University of Minnesota Landscape Arboretum


The All-America Selections gardens this year at the Minnesota Landscape Arboretum were a mix of strange and stranger. For starters was the weather. Snowfall last year was low with minimal moisture content. The growing season--the end of May to the end of July--was cooler than normal. August was a bucket load of moisture but summer came in September with 80 degree temperatures and dry conditions. The 2010 AAS winners featured flowers only. The strange factor about the AAS was the expected colors on certain annuals. We had three outstanding cultivars for the 2010 sneak peek despite four plant diseases in the AAS bed and a crop failure.

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Twinney Peach Snapdragon
(Antirrhinum majus 'Twinney Peach')
All-Americas Selections
Twinney Peach Snapdragon, aptly named for its color, had a double flower form with soft shades of peach, yellow and light orange color tones. This cultivar was quite floriferous--blooming early and up to frost--with a manageable sized 12" height and flowers up to 1.25". We had a fusarium or Pythium disease problem but once that is solved this cultivar will be around for years to come. The plants seem to be weather resistant and relatively maintenance free, for small space garden to any type of container.

Like the Snapdragon, Mesa Yellow Gaillardia was unique with its controlled plant habit and very floriferous flowers that continued to bloom through the summer. Gaillardia attracts butterflies; Mesa Yellow had an improved mounded plant habit of 20-22" in a full sun location.

Zahara Starlight Rose got rave revues on its stunning flowers from volunteers, staff and visitors. A new bicolor for this sun-loving annual, other good traits not found in many Zinnia cultivars included as leaf spot and mildew resistance. What slowed it down was the disease Sclerotinia, which affects other annuals as well. The flower form is a composite single rose and white bicolor growing up to10-12" blooming early and continuing to frost due to its disease resistance. Zahara Starlight Rose is heat and drought resistant and very floriferous.

I can't tell you much about Viola"Enduric Sky Blue Martien" except that we had a crop failure. These three plants are outstanding in their own way and will be grown again next year.

Cottony Grass Scale: A Year Later

Bob Mugaas, University of Minnesota Extension Educator

Jeffrey Hahn, Asst. Extension Entomologist


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Close up of cottony grass scale
Jeffrey Hahn

This past year saw a significant increase in the number of reported cases of cottony grass scale (CGS), Eriopeltis festucae, in Minnesota lawns. In 2007, we were only aware of one reported case of cottony grass scale. By 2008, that number had grown to about 6 newly reported cases with the one from 2007 disappearing entirely as there were no signs of infestation in 2008. However, by the end of September in 2009 the number of reported cases that we knew about rose sharply to between 75 and 100. While these were reported cases and not necessarily confirmed infestations, most recognized and described the symptoms, and ultimately the insect, as that shown in our previous article first describing this insect in Minnesota. (See the December 2008 YnG newsletter). Hence, it appears reasonable to assume that most identifications were likely correct.

In order to get a better feel for the scope and range of this insect in Minnesota, it was decided to conduct a survey of those reporting CGS infestations to us. The survey was conducted with SurveyMonkey.com with potential participants notified via email that the survey had been posted followed by a request that they take a few minutes to complete the survey. All respondents and responses were kept anonymous.

The survey covered a variety of topics ranging from symptoms observed, site conditions where most commonly found as well as cultural and pesticide practices employed to manage and control the pest. Sixteen respondents of about 18 receiving the questionnaire completed the on-line survey. This article summarizes those results as well as provides an update to last year's article concerning CGS In Minnesota.

While our awareness of this pest was first noted in 2007, one survey respondent reported seeing it in 2006 although we are not certain as to its location. In 2007 and 2008 all of the reported infestations were from around the greater Twin Cities metropolitan area. In the survey, CGS was reported in just two sites in 2007 and only nine sites in 2008. In 2009, reports of CGS infestation had expanded to include many Twin City municipalities as well as reports from border counties in western Wisconsin, Mankato, St. Cloud, Brainerd and Alexandria. There may be other locations as well. However, we only have confirmed documentation from those particular areas. In the survey, CGS was observed at 63 - 78 sites. It is unclear why this dramatic increase of reports occurred.

We were very interested to learn if CGS was successfully surviving winters. Of the single site in 2006, the 2 properties in 2007, and the 9 lawns in 2008, CGS was observed on all of same properties the following season. Although not reflected by the survey, we are aware of at least one property where CGS has not been found in two years since it was first found in 2007. Still, this suggests that CGS are capable of surviving winters in Minnesota.

Typically, CGS is observed in August or September, although in a few cases it was noticed in June and July. Late summer coincides with when CGS matures into adults and produces egg sacs. These stages are much more conspicuous as a white woolly material surrounds the insect, making them much easier to see in the grass. The life cycle is still not well understood but this species is reported in the literature to overwinter in Maine in the egg stage. That appears to be true in Minnesota.

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Typical mower wheel track striping pattern
associated with CGS when mowing in one direction
Bob Mugaas

As was noted last year, the most common symptom associated with CGS is the distinctive mower pattern in which the wheel tracks consistent with those of a commercial riding mower remain green and mostly non-infested. This creates a striped pattern where grass is mowed in only one direction or a checkerboard pattern where grass is mowed in two directions and at right angles to each other. See Pictures 2 and 3. The area below the mowing deck varied from light to very heavy infestations of CGS with the corresponding yellow to tan grass blades associated with their feeding. Only two of sixteen respondents reported an infestation that did not show-up in that same pattern. In one of those instances a walk behind rotary mower was used as opposed to a commercial riding type of mower.
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Mower wheel track striping pattern associated with CGS
when mowed in two directions perpendicular to each other
Bob Mugaas


While that sort of mowing pattern suggests that the insects may be being destroyed via a crushing action imparted by the riding mower, it remains uncertain as to whether or not, or how much of that really occurs. Further evidence gleaned from the survey that some type of crushing action is occurring was noted by three of the survey respondents. In one instance, a respondent noted that when the area was rolled using the roller on a lawn aerifier, the lawn improved dramatically within two to three weeks. In another instance, the infested area was rolled with (presumably) something like a sod roller where it was again noted that the lawn recovered 'rather quickly'. In this last case the rolling was done when the cottony, cocoon-like grass scales were present and visible on the grass blades. One respondent noted that by not mowing in the same wheel track pattern each time, thereby destroying another portion of the CGS infestation, recovery of the turfgrass was evidenced by improved green color. See picture 4.

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Comparison of infestation levels in areas
associated mower wheel track and not mower
wheel track areas. No lack of infestation in greener, wheel
track areas compared to areas in between wheels
Bob Mugaas

To the best that we can interpret from survey information, all of the rolling/crushing activity would have occurred when the cottony, sac-like structures were clearly evident. While the above observations are very important in helping us better understand the potential vulnerability of CGS, it is hoped that further investigation and observation will help clarify the specific association with mower wheel tracks and the presence or absence of this pest in those specific, rather narrow areas.

Previous information provided by people encountering this problem indicated that it was primarily found on more highly maintained lawns presumably dominated by Kentucky bluegrass and for the most part receiving full sun exposure. As a follow-up to that anecdotal information, the survey asked respondents to identify the lawn care situations where this pest was being observed. Their choices were as follows:
  • Highly maintained lawns (e.g. regularly mowed, fertilized at 3 to 5 pounds of N per 1000 square feet annually, irrigated, kept green throughout the year)
  • Moderately maintained lawns (e.g. regularly mowed, fertilized at 2 to 3 pounds of N annually, irrigated as needed to keep lawn basically green but some browning tolerated)
  • Low maintenance lawns (e.g. mowed as needed, not irrigated at least with any degree of regularity, fertilized with 1 or 2 pounds of N annually, brown grass associated with summer dormancy is tolerated)
Twelve of the sixteen respondents indicated that this was a pest primarily infesting more highly maintained, Kentucky bluegrass lawns thus lending credence to what others were saying as well as our own observations. Only three indicated a presence on moderately maintained lawns and only one respondent noted CGS presence on a low maintenance lawn. While not asked directly in the survey, personal observation of infested sites along with input from others indicated that this pest is not as attracted to the fine fescue (only two reports) lawn grasses. While their presence was noted on the fine fescues it was in much smaller numbers than that observed on Kentucky bluegrass. In another sighting, it was observed that the creeping bentgrass growing in the same area as Kentucky bluegrass was not infested while the surrounding Kentucky bluegrass was heavily infested. See Picture 5.

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Photo 5: Note non-infested creeping bentgrass compared to surrounding Kentucky bluegrass. Here Peter Fanjul.

From this limited amount of field observation, it would appear that well maintained, predominantly Kentucky bluegrass lawns, are more likely to be infested with CGS than those lawns receiving moderate to low levels of maintenance. With this being a relatively small sample size, further observation and monitoring will help confirm any turfgrass species preferences of this pest.

While the level of sunlight received by the infested areas was not specifically asked in the survey, it would generally be assumed that an otherwise healthy, more highly maintained Kentucky bluegrass lawn would be located in an area receiving full to mostly sunlight conditions. However, there are at least two reports, one from the survey and one not, that did observe CGS in partially (tree) shaded areas of the lawn. In light of where this pest appears to occur most frequently, it would appear that its preference would be for actively growing Kentucky bluegrass in mostly sunny areas. However, its occurrence in more shaded situations cannot be ruled out. Again, future monitoring and observation should help clarify site and plant material feeding preferences of CGS.

Another aspect of CGS management that the survey helped assess was whether or not the implementation of any particular cultural practice or change in cultural practice helped improve the turfgrass stand (i.e., symptoms abated and grass color and vigor improved). Ten of sixteen respondents tried making at least one cultural practice change compared to what was previously being done. Those cultural practices asked by the survey included:
  1. use of more or less water
  2. use of more or less nitrogen
  3. mowing heights increased or decreased
  4. mowing frequency less often or more often
  5. lawn dethatched only, lawn aerified only or, lawn dethatched and aerified.
Four of the ten respondents who indicated the implementation of at least one cultural practice change noted that the lawn improved following those practices during the same growing season. Two respondents reported no improvement.

There was no clear pattern of practices that seemed to be any more helpful than another. For example, the one respondent who indicated that they 'aerified only' reported improvement in the turfgrass similar to two respondents who utilized four different practices including the use of aerification. Of the two respondents that increased water or chose to mow less often, both indicated seeing no improvement in the turfgrass. A respondent who indicated an increase in N and mowing higher was uncertain as to whether or not the situation had improved. However, that same respondent did indicate that use of Merit alone or with cultural practice changes (presumably those mentioned above) resulted in improvement in the turfgrass stand. When changes in cultural practices were combined with the application of an insecticide, four of six respondents noted an improvement while two noted no improvement.

While there appears to be a clearer understanding as to this pest's preference for well maintained lawns, it is not as clear as to which cultural practices might be more important in either encouraging or discouraging the establishment of and/or maintaining an existing pest population. Also, there does not seem to be a clear cut pattern of control using pesticides alone or with a particular set of cultural practice changes. For example, of the two respondents who indicated that they reduced water and nitrogen amounts and used an insecticide (Merit), one noted improvement while the other did not.

Eight people applied insecticides to attempt to manage CGS. Two used Merit and both believed these applications decreased the population of CGS. One applicator also treated his lawn with Talstar (bifenthrin) but did not think it was effective. One respondent used both Merit and Talstar believing that this was effective management. Likewise, one person used Scimitar (lambda cyhalothrin) and thought he gained a reduction of CGS. There was also a single record of acephate although they did not record whether they thought it was effective. Another person used horticultural oil but didn't know whether it was effective.

It is interesting that the insecticide applications appeared to improve the turf in some cases. Although Merit should be effective, it would not be expected to have an impact on CGS numbers until the following spring. We would not expect any of the residual insecticides (Talstar, Scimitar, horticultural oil) to be effective on adults, although they would be effective against crawlers if you were able to time the application when they were present.

Eight out of nine people that did nothing did not see an improvement in the turf in the same season. There was one respondent that said the turf was looking good again by late October. It will be particularly interesting to observe infested lawns next spring to see whether they have recovered or not. It has been our observation to this point that turf does improve without any lasting injury. With many more properties to examine, this will help us determine if this generally true.

In summary, it is understood by the authors that this survey represents a relatively small number of respondents. Nonetheless, it is an attempt to gather rudimentary yet useful information about CGS presence, habits and control strategies being utilized in Minnesota to manage this pest. It is hoped that our own further observation and monitoring plus valuable input from the lawn care industry will continue to provide an expanding data base on CGS management. From that information, effective IPM strategies can be developed and refined to provide lawn care personnel as well as homeowners with a variety of effective management and control options for CGS.

December 2009 Garden Calendar

Karen Jeannette, Yard and Garden News Editor
Including excerpts from the 2009 Minnesota Gardening Calendar

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Korean pine tree in the MN Landscape Arboretum pine collection
MN Landscape Arboretum

It's not too late to protect your plants from Minnesota winter sunscald, animals, salt, snow, ice, and winter discoloration.  See: Protecting Trees and Shrubs Against Winter Damage

Mulch when the ground is frozen to keep the ground frozen, by applying a 4 - 6 inch layer of mulch (i.e. clean straw or leaves) over perennials or at the base of trees and shrubs.  Mulching to keep the ground frozen will help prevent those soil freeze-thaw cycles that can cause damage to roots and heaving of new plantings and perennials above the soil line.

Need to review which trees to select for Christmas?  See Kathy Zuzek's December 2008 article: It's Time for the Christmas Tree
 
Is your yard or garden ho-hum this time of year? Get inspired with Plants for Winter Interest  or visit your favorite full-size evergreens at the Minnesota Landscape Arboretum's arborvitae, pine, spruce, and dwarf conifer collections.

2010 Minnesota Gardening Calendar


The 2010 award winning 12-month Minnesota Gardening Calendar is available for sale. Full color photographs highlight each month. Also find timely tips for lawn, garden, and houseplant care, with a special feature: Using Vines in Minnesota Home Landscapes. Maps of average frost-free dates and USDA Plant Hardiness Zones for Minnesota are included. Extension's 18 Regional Centers are listed and information about horticultural programs, services, facilities, and
organizations in Minnesota are featured.

See a web preview and ordering information @ http://www.extension.umn.edu/distribution/horticulture/08632.html

Below we share the 2009 December Minnesota Gardening Calendar tips:
  • Check Christmas tree stands daily, so they never run out of water.
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    Photo 2: 2010 Minnesota Gardening Calendar.
    Paperwhite narcissus are wonderful winter flowers. Buy some bulbs for yourself and to give as gifts.  With clusters of small flowers in white, cream, or yellow, they need to special treatment to bloom.  Plant them in pebbles or soil; just keep the base and roots wet.  Paperwhites do best in a cool location with good sun, but will bloom anywhere -- albeit on floppier stems that will need staking or tying to stay upright.
  • Choose a fresh Christmas tree that meets your needs. Balsam fir is more fragrant; Fraser fir is also fragrant and very popular. Norway pine has stiff branches and needles that will hold heavy ornaments, while white pine has fragrant needles that are softer and longer -- more appropriate for lightweight ornaments.  White spruce is excellent as a table-top tree, as is the tropical houseplant, the Norfolk Island Pine.
  • Though poinsettia sap may be irritating, the plant is not toxic when eaten. Unfortunately, some traditional holiday plants can be dangerous if eaten, though especially by a small child.  Set holly and mistletoe out of reach, and dispose of any berries that drop off.  Ornamental peppers aren't poisonous, but they can be so "hot" that tasting them, or even handling them and rubbing your eyes can be painful.
  • Take time to check stored dahlia tubers, canna bulbs, and produce such as potatoes or winter squash.  Look for shriveling, soft spots, mold, or other signs of trouble.  Discard damaged bulbs and tubers. Often rotting is a sign the bulbs were wounded when they were dug up, or that storage temperatures are too high or there's insufficient air circulation.

Monday, November 2, 2009

An Interesting Insect Found In a Home Yard

Jeffrey Hahn, University of Minnesota Asst. Extension Entomologist

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 Northern mole cricket
Jeff Hahn
An unusual insect, a northern mole cricket (Neocurtilla hexadactyla), was submitted to the entomology department in August. This insect was found by a homeowner in their yard in North Branch (Chisago county) in east central Minnesota. Northern mole crickets are found throughout the eastern U.S. in low lying moist areas, e.g. along the margins of lakes and streams. They are rarely found in home lawns and are not considered to be a pest in Minnesota.

This brown insect grows up to 1 1/4 - 1 1/3 inches long, has moderate length antennae and short wings that only extend about half way down its abdomen. What is particularly distinctive about this insect is its stout, mole-like front pair of legs which are modified for digging (called fossorial). They have four dactyls (claws) on their tibia which distinguishes them from closely related mole crickets. Despite their ungainly appearance, northern moles crickets are capable of flight, flying at dusk.

They spend essentially their entire life underground where they feed on grass. If a northern mole cricket is exposed, its first reaction is to dig back down into the soil.

They take two years to develop into adults. Females lay eggs in spring in chambers in the soil. The immature nymphs develop slowly and spend the first winter as nymphs. They eventually mature the second year wintering as adults.

A northern mole cricket is a relatively uncommon insect in Minnesota, but even less commonly noticed by people due to its secretive habits. Interestingly, a number of eastern states also reported encountering this insect this summer in instances when they normally do not. It will be interesting to see if this a future trend or if this year was just a good year for northern mole crickets.

Fungi Sprouting on Trees Have a Scary Story to Tell

Michelle Grabowski, University of Minnesota Extension Educator

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Photo 1 (left): Basidocarp of Climacodon septenrionalis. Michelle Grabowski.
With October's frequent rain, many gardeners have noticed fungi sprouting from some landscape trees. These fungi may be any number of shapes, sizes and colors. They may arise from the trunk itself, from the root flare of the tree or from the roots. In all cases, fungi growing directly on a live tree tell the tale of heart rot within.

What's in the Trunk?


In order to understand heart rot, gardeners must understand a little bit about the wood within a tree trunk. Trees can have several different kinds of wood within their trunk. Sapwood is composed of living cells with a number of jobs to do. Sapwood cells conduct sap through the tree, store extra energy, close off wounds, and actively fight invading microorganism. In all trees, sapwood occurs in the outer most rings of the tree. Some trees, like maple, birch, beech and poplar form only sapwood. Other trees also form a second type of wood, known as heartwood at the core of their trunk. Heartwood cells are dead cells that serve primarily to add structural support to the tree. Heartwood cells contain a number of toxic chemicals that protect the heartwood from wood decay fungi. How well these chemicals protect the heartwood varies from tree to tree. Trees like cedar and redwoods are so effective at defending against wood rotting fungi that their wood is highly valued for use in wood products like lumber.

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Photo 2 (above): Internal decay shown on cut trunk.

Heart rot can cause decay in both heartwood and sapwood. Many different fungi from the phyla Basidiomycota, can cause heart rot. These fungi are often seen on rotting logs or dead trees as well as on living trees. The mushrooms, shelf fungi and other interesting fungal structures that emerge in wet weather are spore producing structures of the fungus, and are generally known as basidiocarps. If a basidiocarp is observed on a live tree, it indicates that there is rot within the tree. Basidiocarps can be used to identify the specific fungi causing rot as they are often unique to a specific genera or species of fungus.

How the Invasion Begins


Heart rot fungi are not aggressive pathogens and are unable to infect a tree through intact bark. Instead heart rot fungi take advantage of wounds from lawn mowers, weed whips, fire scars, deer rubbing, rodent chewing, frost cracks, broken branches and other injuries to access the sapwood and heart wood. Some heart rot fungi can also enter a tree through an old branch stub or through the trees roots. Once inside the tree, the fungi use a variety of enzymes and other chemicals to breakdown the wood for food.

The Progress of Decay


White rot fungi breakdown all components of the wood including lignin, cellulose and hemicellulose. Trees suffering from white rot have soft white wood that is stringy, spongy, or crumbly to the touch. Brown rot fungi break down cellulose in the wood but not lignin. Trees suffering from brown rot will have brown decaying wood that breaks apart into cube like chunks. This type of rot is often called brown cubical rot. In both cases advanced decay can significantly reduce the strength of the tree resulting in fallen branches or trees that break or fall over. Trees often survive many years with heart rot. Internal rot often goes unnoticed for years because the tree can continue to grow with no symptoms of disease or decline in the canopy. Remember heartwood cells are not living cells and serve only to provide structural support for the tree. If basidiocarps are observed on the tree, it is likely that the tree has already been infected for several years. The decay caused by many heart rot fungi progresses very slowly, often at a rate of about 3 inches per year.

Assessing Damage in an Infected Tree


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Photo 3 (above): Fungi, indicating butt rot on maple. Michelle Grabowki.
A tree with signs of heart rot does not need to be immediately removed, but it should be further examined to determine how structurally sound it is. Special care should be taken with trees that are located near people or property that could be damaged by fallen branches or trees. In natural areas, trees with heart rot serve a valuable function in providing nesting sites for birds and animals and should be left undisturbed if possible. The stability of a heart rot infected tree will vary depending on the type of tree that is infected, the extent of the decay, the type of rot, and if other defects like cracks or cavities are present. The USDA Forest Service (http://www.na.fs.fed.us/spfo/pubs/hazardtrees/treehazards/rec.htm) recommends that action be taken to stabilize or remove a tree if it has signs of a heart rotting fungi and one or both of the following:
  •  a crack, open wound or other defects are also present

  •  less than 1 inch of solid wood for every 6 inches of tree diameter.
The level of internal decay can be difficult to determine if an open cavity is not present. Gardeners concerned about the structural stability of a tree should contact the local city forester or a certified arborist (www.treesaregood.org). These professionals can run a variety of tests to help assess the stability of the tree.

Preventing Heart Rot in Trees


Gardeners can prevent heart rot by protecting the trees most important natural defense - its bark.
  • Take care not to wound trees with lawn care equipment.

  • Protect trees from deer rubbing and rodent damage with fencing.

  • Use proper pruning cuts when pruning trees and never leave a branch stub (see: http://www.extension.umn.edu/yardandgarden/YGLNews/YGLNewsMar12007.html#pruningcuts).

  •  If branches are broken during a storm, cut damaged branches with a proper pruning cut below the damaged area. The tree will be able to heal a smooth pruning cut more quickly than a rough jagged rip.

Dormant Seeding Lawns: Last chore of the season?

Bob Mugaas, University of Minnesota Extension Educator

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Photo 1 (above): Thin lawn area that could benefit from dormant seeding. Bob Mugaas.

One last shot at lawn improvement can be done even yet this fall. By early November, most lawn care chores and activities are completed; lawn mowers are put away, watering has ended, hoses are drained and stored for the winter, irrigation systems have been blown out and winterized and, the last, late season nitrogen fertilizer has been put down.  Yet, there remains one activity that can still be done to help repair or thicken the lawn for next year. In fact, prior to the early part of November (at least in the Twin Cities area, earlier in the northern half of Minnesota), it would be have been too early to do this task. That task is known as dormant seeding.  It is best employed when wanting to reseed bare soil areas or help thicken up thin lawns. It is not as effective, where lawns are thick and dense with little opportunity to achieve the good seed to soil contact necessary for the grass seeds to germinate and grow next spring.

The Dormant Seeding Process


Dormant seeding involves putting down seed while the ground is
not frozen, yet cold enough so germination of the grass seed will not
occur until next spring when the soils begin to warm. In fact, seeds
that do germinate late in the season often do not survive the winter
because the very young, immature seedlings have a difficult time
surviving those harsh conditions. Other than the time of year of dormant seeding, the
actual process of preparing the area to be seeded is virtually
identical to establishing grass from seed at other times of the year.

Choosing Well Adapted Seed


When choosing the seed to use, be sure to select seed mixes that are well adapted to both your site conditions and the amount of maintenance you expect to provide during the growing season. For average lawn conditions, mixes containing some Kentucky bluegrass, fine fescue and small amounts of perennial ryegrass can be sown about three to four pounds per 1000 ft2.

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Photo 2 (left and above): Vertical rotating tines of a vertical mower, sometimes termed a power rake. Bob Mugaas.

Establishing Good Seed to Soil Contact



Success of any grass seeding process depends largely on good seed to soil contact. Therefore, the initial step in preparing the area is to loosen the soil surface so the seed can easily be incorporated into the surface half-inch or so of loose soil. Small areas of bare soil or even a thin turfgrass stand can easily be prepared using a hand rake. Larger areas of sparse turfgrass can be prepared by 'lightly' going over the surface with a power rake or vertical mower available from most rental agencies. Set the blades just deep enough to penetrate into the top ¼ inch or so of soil. This will also help remove small thatch layers that may be present, as well as any dead grass plant parts laying on the surface of the soil.

Rake up the grass plant debris that was brought to the surface from this process so that it will not interfere with sowing the grass seed. This debris can easily be composted or used as a mulch in another area of the landscape. Remember these units are NOT intended to be used as rototillers. They are designed and used to remove thatch with only light penetration into the surface soil. Hence, use them appropriately; your rental service will appreciate your proper use of their equipment.

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Photo 3 (left): Using a vertical mower to prepare lawn/soil surface prior to seeding. Bob Mugaas.

Another machine known as a slit seeder could also be used. This machine creates a shallow slit in the soil into which the seed is dropped, lightly covered and packed down. There are some rental businesses that have such a unit available. More commonly this is a practice hired done by a lawn care professional.

Watering Thoroughly, but Not Too Much


Once the seeds have been properly sown and lightly incorporated into the existing soil, water the area thoroughly and leave until next spring. By this time of year, our cool to cold temperatures and short days will help keep the areas moist far longer than in summer. While just barely damp soil is okay, it is important that the area does not become soggy and saturated with water. If the weather does turn a little warmer and drier and the area starts to dry out,  it may be necessary to lightly water the area just to keep it damp and prevent it from becoming too dry.  However, in most cases it will be unnecessary to do this.

What to Expect for Next Spring


Above are the essentials for the process known as dormant seeding. The degree of success from your dormant seeding efforts will depend on the overwintering conditions afforded to the newly seeded areas. In most cases, the seed is best protected when we receive snowfall(s) that will cover and protect those areas during fluctuating weather conditions often experienced during a Minnesota winter. Even with good preparation, it may still be necessary to do some overseeding in the spring in those areas where little grass emerges. If the newly seeded areas appear to be a little thin, you shouldn't necessarily feel your fall efforts were a failure, as it is quite common to have to do a little additional reseeding in the spring. However, do allow enough time for the seeds to come up the following spring. Don't be too hasty to get in and start tearing things up; you just may be destroying all of the good work done the previous fall.

For those of you who postponed doing some lawn seeding earlier last summer, consider doing some dormant seeding yet this fall. It may be just the ticket to give you and your lawn a jump start next spring.

Edible Landscape Wrap-Up

Emily Tepe, University of Minnesota Research Fellow, Department of Horticultural Science

After many weeks of harvesting mountains of chard, tomatoes, zucchini, peppers, cucumbers, raspberries and a multitude of other vegetables, fruits and herbs, the University of Minnesota Edible Landscape has been put to bed. Well...almost. The few lone stands of silvery blue kale seem to mock the cold, their leathery leaves sweetening with each frosty night. And many of the herbs are even holding onto their green. Other than those, the Edible Landscape is now resting after a long and productive season. snow on kale_tepe.JPG
Photo 1 (left and above): Snow on dinosaur kale in the University of Minnesota Edible Landscape on October 12, 2009. Emily Tepe.

If you haven't had a chance to see the gardens on the St. Paul campus this year, and if you haven't been following the Edible Landscape blog, here's a rundown of some of the details of the project. The Edible Landscape filled four beds outside the Plant Growth Facilities on Gortner Ave. The 1500 square foot garden was comprised of 75 varieties of fruits, vegetables, herbs and flowers. The garden was designed to emphasize the ornamental qualities of edible plants, and demonstrate how these plants might be incorporated into the home landscape in creative, attractive ways. Most of the ornamentals, herbs and warm season crops were started from seed in the greenhouse during the winter months. Others, such as chard, kale, summer and winter squash, melon, lettuces and radishes were direct seeded throughout the season. By mid-October, almost 500 pounds of produce had been harvested from the Edible Landscape and shared with students, faculty and staff in the Department of Horticultural Science.

After cleaning all the annuals out of the garden (which were then composted), winter rye seed was raked into the beds for a winter cover crop. It may sound strange to think of cover crops in a home gardening demonstration. After all, we normally think of cover crops being used on acres of land, not in the backyard. But cover crops in the home garden can offer great benefits such as weed suppression, erosion control, increased microbial activity and moisture retention, just to name a few. You can read about Green Manure Cover Crops for Minnesota on the U of MN Extension Website.

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Photo 2 (right and above): The largest bed in the University of Minnesota Edible Landscape in mid-July. Emily Tepe.

If the idea of edible landscaping sounds intriguing, or if you would simply like to learn more about this project, visit the Edible Landscape blog. The entire season was documented on the blog, which is filled with photos, design ideas, plant lists, growing information and more. Now that the harvests have finished, and the season is being evaluated, there will be more discussions on the blog about plant combinations that worked well, successful varieties, and lessons learned. Read, learn, share and join the discussion.

Thursday, October 1, 2009

Field Guides Can Be Fun

Jeff Gillman, Nursery Management Specialist


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Different people collect different things. Some like baseball cards, some like shoes, and some like coins. I like books about insects. No, really, I do. Just glancing up from my desk I can count something like 5 field guides, 10 general entomology texts, and a slew of others that fit into categories like insect control, insect taxonomy and insect physiology (I have a lot more at home). If you were to spend some time with these books you would discover rather quickly that, all in all, entomologists are boring writers. No zip, little spark. And that, in a nutshell, is why I like Jeff Hahn's new book Insects of the North Woods so much.

Photo and Cover: Insects of the North Woods, by Jeffrey Hahn. © Kollath-Stensaas Publishing.

Just looking at the cover of Insects of the North Woods you might be convinced that this is just a typical insect field guide. It's got some pretty pictures and, on the back, the obligatory author photo. But when you open the pages of this book, you quickly discover that it is not only as informative as you would expect from a University of Minnesota Entomologist, it's also entertaining. This book literally drips with Hahn's personality and sense of humor. Between talking about receiving a gift of a dead insect being every woman's dream when referring to scorpion fly mating rituals, and the mini scuba tanks that predaceous diving beetles use, you soon come to realize that this isn't just an entomologist reciting dry facts. Instead, this is an author who loves his subjects and who wants the reader to love them too. Like most people, I don't read field guides cover to cover, but with this book I have often found myself going through the book page by page because I don't want to miss one of Hahn's insightful comments (or one of his amusing analogies).

Besides the writing, this field guide has everything else that you'd expect a field guide to have, including great pictures (mostly by the author), a nice index system for finding the insect you're looking for, and a good, but not overly-done introduction. Though this guide concentrates on insects of the North Woods and so is, at least in theory, intended for use in northern Wisconsin, Michigan, and Minnesota, it is also the best book available for identifying insects in forests around the Twin Cities area and is a great first field guide for any budding entomologist. If you enjoy insects, or if you're just interested in knowing what some of the insects that flit about your trees are, then you shouldn't miss this book.

What's Up With That?!

Birch Abnormal Growth Syndrome (BAGS) aka. Mouse Ear Disorder

Carl Rosen, Extension Soil Scientist and Karl Foord, Extension Educator

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The strange leaf symptoms on this river birch tree, taken on August 7 (Photo 1, left) were diagnosed as birch abnormal growth syndrome or BAGS. New leaves are severely stunted and take on a mouse ear appearance. For many years the cause of this disorder was a mystery, but it is now known to be due to a deficiency of nickel.

Photo 1 (left): River Birch 'Summer Cascade' at planting time showing symptoms of nickel deficiency (BAGS). Photo taken August 7, Karl Foord.

Nickel is an element only recently shown to be essential for plant growth and is required in very small amounts. Almost all soils have enough nickel to support plant growth, but under some conditions, nickel deficiency can still occur. The mouse ear symptoms on this river birch were first seen when growing in a peat-based container mix, and were initially misdiagnosed as bud damage from a late frost. However, after the tree was transplanted into the soil in mid-May, the symptoms, after continuing for the next few months, have now begun to appear normal.10-1-09_Med-Summer Cascade Birch mouse ear.j_CarlRosenpg.jpg

Based on research conducted at the University of Minnesota and in other areas of the country, BAGS almost exclusively occurs on river birch when grown in peat-based media and can be corrected by soil or foliar applications of nickel.

Photo 2 (right): Close up of 'Summer Cascade' river birch leaves with BAGS. Photo taken August 7, Karl Foord

Research has also shown that when soil is added to the peat media (20-30% by volume), the nickel deficiency symptoms will not occur, suggesting that there is enough nickel in the added soil to meet the nickel requirements of the plant.
10-10-09_Med_nickeldefonriver birch_carlrosen.jpgIn cases where the symptoms are most severe, an analysis of the peat has shown excessively high levels of zinc. These high levels of zinc in the peat likely accentuate the nickel deficiency. Therefore, adding soil to the peat mix may help by 1)alleviating BAGS symptoms by adding the needed nickel,  and 2) by tying up or diluting some of the excessive zinc in the peat.

Photo 3 (left): Up close. Mouse ear symptoms of nickel deficiency on peat-based media. Carl Rosen.

As shown by the picture taken on September 14 (Photo 4, below), the tree has nearly recovered from its mouse ear symptoms and is expected to make a complete recovery once the roots have fully established into the native soil. 

10-1-09_Med-Summer Cascade Birch 9 14 2009 recovered_KarlFord.jpgIn general, BAGS has been a problem most apparent to the nursery industry, as trees showing the symptoms are usually not sold. However, if the problem does occur in containers, it can be corrected with nickel applications or by transplanting to a medium containing at least 20% soil. Soils in Minnesota have enough nickel to support plant growth, therefore nickel application to river birch growing in the landscape is not necessary.

Photo 4 (left): Recovery of river birch 'Summer Cascade' from BAGS.  Photo taken September 14, Karl Foord.
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