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Tuesday, September 1, 2009

September gardening endings and beginnings

Dear Yard and Garden News readers,

September represents both an ending and a beginning to me (see the 2009 September gardening list and tips related to these beginning and ending activities). It represents a time that much of the garden is hitting (or has hit) its peak and must become prepared for winter rest. Yet September brings with it another growing season's knowledge and discovery in which a gardener can formulate his or her new future gardening plans for the next year. As your new University of Minnesota Extension Yard and Garden News editor, it is with great enthusiasm, that I look forward to continuing the tradition of helping gardeners and yard caretakers in Minnesota become connected with the horticultural science and research that manifests itself into useful gardening information, tips, and discoveries.

Before I move forward with this and other issues, I would like to thank David Zlezak and past editors for producing and developing what I have always experienced as interesting, intriguing, and informative Yard and Garden News. The Yard and Garden News has always been a central place for me to stay connected to University of Minnesota horticulture research and information.

Before David crossed the Minnesota-Wisconsin border to take his new position as assistant professor at University of Wisconsin - River Falls, we had an opportunity to discuss and brainstorm infinite and exciting possibilities for Yard and Garden News readers. Similar to David, exploring gardening and horticulture is what led me to pursue both undergraduate and graduate degrees in horticulture. Even after two horticulture degrees, I'm still just as curious and interested in knowing the what, how, and why for just about everything plant-related (In fact, more education just makes me aware of how much more there is to know that I don't know!). Whether you read the Yard and Garden News with the same spirit of curiosity and interest in the science-based "when", "why", or "how", or whether you just want to find out what gardening methods or yard care tips the University of Minnesota Extension recommends so you care for your garden and yard in a way that meets your personal goals, I hope you will all join me in this and future editions of the Yard and Gardens News.

As the gardening season is winding down, the Yard and Garden News will be issued once per month. We will continue to be here for you with the standard monthly issues and a wealth of information available to you in the ten years of archived issues. Thank you for your faithful readership of the Yard & Garden News. Please look forward to the next issue of the Yard and Garden News October 1, 2009.

Happy Gardening!

Karen Jeannette
Yard and Garden News Editor
University of Minnesota

The Yard and Garden News: Features in blog format

Karen Jeannette, Horticulture Research Fellow & Yard and Garden Editor

Last month, former editor David Zlezak explained the Yard and Garden News has moved to a blog format.  Here we explain a little bit about how this new type of format has enhanced options, but still the same quality information you've come to depend on. These are some new features:

  • Readers can comment on articles - we want to hear from you!
  • RSS feeds - read Yard and Garden News in your favorite feed reader
  • View articles chronologically (under Archives) or by topic (under Recent Posts) - choose what works for you
  • More options to use media (video, voice, slidshows, etc...) to support articles
We encourage you to explore these new features, or you can sit back, relax and read the Yard and Gardens News as always. You will continue to receive email notifications linking to new Yard and Garden News articles.  And don't forget: The old Yard and Garden News archive is still accessible from the new site by searching for information under the  "Search 1999-2008 archive" (see left column).

Printing and photo captions

With the switch to the new format, we are still working on improving printing and photo caption options for our readers.

Printing instructions: To print the newsletter in blog format, click on the desired month in the archive (right column), then select print from your computer's file menu. Note: When printing pages, you currently may be experiencing the text clipped a bit short around the margins. We hope to resolve this problem in the next few issues. We appreciate your patience while we are working to get this problem corrected.

Photo captions: The blog format does not currently have the ability to produce captions around the images. Until this is corrected, we will be providing descriptions and photo credits in the body of each article.
We want to reassure our readership that your Yard and Garden News team is working to correct these printing and photo caption issues. We hope you'll enjoying using the new blog format. We're excited about the additional possibilities for sharing the latest Yard and Garden News with you.

A Honeydew List

Jeffrey Hahn, Asst. Extension Entomologist

There have been various reports lately of trees weeping or dripping some kind of sticky substance. There have been different speculations about what causes this problem. Is it some kind of disease? Is it just sap? The answer: insects.

Photo: Typical aphids.  Jeff Hahn.

Aphids and certain scale insects feed in the phloem layer of plants using their needle-like mouthparts. They are not able to digest all of the sugars in the sap, and consequently, excrete a sugary liquid called honeydew. Honeydew is clear (can appear white) and is sticky. This material is not harmful to the health of trees but can be annoying when it coats deck furniture, cars, or other objects that are below infested trees. If this is a problem, try to remove it as soon as possible as honeydew can be very challenging to remove the longer it stays on.

Many ant species enjoy sweets and are attracted to honeydew. Some ants actually tend aphids to maintain their supply. Yellowjackets change their dietary habits during late summer and fall and are quite interested in the sugary content of honeydew. There can be so many yellowjackets attracted to a tree infested with aphids or scales that people may think that there is a nest in the tree.

Predators, especially lady beetles,may also be indirectly attracted to the honeydew. Of course they are interested in the aphids or scales that are producing the sugary liquid. One resident wanted to have a lady beetle larva identified. They were concerned because their tree was 'weeping' and these larvae were present. The owner was convinced that the larvae was causing the weeping and as a consequence started spraying them with an insecticide. Of course the lady beetle larvae were there to eat the aphids which were producing the honeydew.

Another consequence of honeydew is that it supports a fungus called sooty mold. Like the name suggests, it is black and sooty in appearance and is found on branches and leaves where honeydew is found. Although it is unsightly, sooty mold does not harm plants and should be ignored.

If you have a situation where you would like to reduce aphids, whether from the nuisance of the honeydew or from the insects themselves, there are several environmentally friendly options you can take. First, you can take a hose and direct a hard spray of water at infested leaves and branches. This knocks them off, effectively killing them. You can also apply a low impact insecticide, especially insecticidal soap or horticultural oil. These kill aphids while preserving natural enemies like lady beetles, lacewings, and syrphid fly larvae. Or just ignore them. As we approach fall, their activity slows down and they eventually stop producing honeydew.

Is late blight a threat to Minnesota tomatoes?

Michelle Grabowski, University of Minnesota Extension Educator

Thumbnail image for 9-09LateBlight 1.JPGMany articles about the late blight epidemic of potatoes and tomatoes in the northeastern United States have been appearing in the news this summer. These reports are making some Minnesotans worried about late blight here in Minnesota. Although the extreme level of disease that is occurring in the northeast is not currently present here in Minnesota, late blight is present in the state and disease is possible. Gardeners should be aware of what late blight infected plants look like, what environmental conditions favor late blight, and what to do if late blight occurs. At this point, however, there is no need to panic.

Photo 1: Late blight on leaves. H.Schwartz, Colorado State University,

About late blight

Late Blight is a disease caused by a fungus-like organism called Phytophthora infestans. Phytophthora literally means 'plant destroyer' in Latin. This pathogen has earned its name by causing several famous epidemics including the Irish potato famine of the 1840's that resulted in the death or emigration of millions of Irish people. Late blight is most severe on potatoes and tomatoes but can also infect related plants like petunias and nightshade. Olive brown spots on leaves or stems are often the first obvious symptoms of disease. These spots grow until the entire leaf is affected, progressing into petioles and stems. Eventually the entire plant is brown and wilted. Under very moist conditions, fine white cobweb like fungal growth may be visible on infected plant parts. Infected tomato fruit have a large greasy brown spot. Infected potato tubers have sunken brown lesions on the surface and reddish granular rot extending into the flesh of the potato. Rot can start in the field and continue in storage.

Thumbnail image for 9-09LateBlight2.JPGPhytophthora infestans thrives in cool wet weather. Temperatures ranging from 60-80 degrees F are ideal. In addition, moisture on leaves and other plant parts is necessary for the pathogen to infect and spread. This moisture can come from rain, irrigation or dew. The late blight pathogen is so devastating because once an infection starts the pathogen reproduces and spreads very rapidly. One lesion can produce 100,000 to 300,000 spores in the right weather conditions. These spores are carried on wind or splashing rain to other plants, devastating an entire field in as little as a week's time.

Photo 2: Late blight causes olive brown lesions on stems. Photo credit: H.Schwartz, Colorado State University,

2009 late blight epidemic in northeastern states

In the northeastern states this summer, several factors combined to create the perfect conditions for a late blight epidemic. First, Phytophthora infestans was brought into several states on infected tomato transplants. These infected plants were then sold at big box stores and distributed throughout the area in home gardens. This early season arrival of the pathogen, combined with unusually cool wet weather, allowed the disease to take hold and spread rapidly from gardens to farm fields.

2009 Minnesota late blight outlook

Until August, most of Minnesota was extremely dry with a few areas in moderate to severe drought conditions (US drought monitor - link to ). These conditions are not favorable to late blight and it is not surprising that the disease was not found in Minnesota until August.

9-09LateBlight 3.JPGWith recent rains, the possibility of late blight on tomatoes and potatoes in Minnesota has increased. Although very few cases have been reported in Minnesota, late blight has been found in North Dakota, South Dakota and Wisconsin. Because the disease spreads so rapidly, there is still time for damage to be done. In large part, the spread and development of late blight in Minnesota will depend on the weather conditions, but spread and disease development also depends on growers and gardeners properly caring for plants that may become infected. Commercial potato growers are already vigilantly looking for new late blight infections and have been spraying fungicides to protect their crop

Photo 3: Late blight on tomato fruit. R.Wick, University of Massachusetts,

Monitoring and controlling late blight

What can you do?
Thumbnail image for 9-09LateBlight 4.JPG
  1. Monitor: First monitor tomatoes and potatoes in your garden at least once a week, and more frequently if rainy weather persists. Examine the lower and inner leaves where humidity is highest and disease is most likely to appear first. Use the UMN extension online diagnostic tool to identify the problem you are seeing on your tomato plant or send a sample to the UMN plant diagnostic clinic (

  2. Remove diseased plants: If late blight appears, immediately remove the infected plant, place it in a tightly sealed plastic bag, and throw it in the trash. This will prevent the pathogen from spreading to nearby gardens and farms.

  3. Apply fungicides: Some gardeners may choose to protect their tomatoes and potatoes with a fungicide spray. Chlorothalonil is the only product available to home gardeners that will provide adequate control of late blight. The vegetable being sprayed MUST be listed on the fungicide label, and all label instructions MUST be read and followed. Organic gardeners can use a copper based fungicide, but should be aware that it will only provide partial protection. Fungicides must be applied before the disease starts in order to control the disease.
Photo 4: Late blight on potato.

S.Bauer, USDA ARS,

 With luck, the season will pass without further disease development. The active management strategies already in place by Minnesota farmers will reduce the amount of fungal spores available to spread the disease. Gardeners can do their part by keeping a watchful eye over their plants and responding quickly if disease occurs.

Lawn care checklist: late summer - early fall

Bob Mugaas, University of Minnesota Extension Educator

Fall lawn care cultural practices employed during the active fall growth period of our grasses can be some of the most important and beneficial activities for your lawn. These practices will aid in good winter survival, early spring green up and growth, as well as provide many other helpful benefits.
Photo 1: Bluegrass lawn recovered from early season drought stress. Bob Mugaas.
With the return of rainfall and moderate temperatures, many of our lawns have come back to life after drier than normal conditions during May, June and early July. With that regrowth beginning, now is a good time to start getting your lawn in tip top shape for the active fall growing period. Below are some good cultural practices to consider.

Seven fall lawn care practices to consider

1. Overseeding and sodding: If the lawn did suffer some permanent injury during the dry conditions of late spring and early summer, now is a good time to do some overseeding or resodding to repair those areas. The very best time of the year to sow grass seed is from about the middle of August to the middle of September in the Twin Cities area. To help ensure a successful overseeding, lightly work the seed into the soil and then keep the area uniformly damp, NOT SOGGY, until seeds start to germinate and emerge from the soil. As the new grass plants get taller and more established, watering can be done a little less frequently but with more water applied per application.

2. Fertilizing: The period right around Labor Day is an excellent time to put down an application of fertilizer. Putting down about one pound of actual nitrogen at this time of year helps provide the plant with the necessary available nitrogen needed to support and sustain active grass plant growth through the fall period. Taking a soil test will help determine whether or not you need either of the other primary nutrients, phosphorus or potassium. Find University of Minnesota Soil Testing Lab at: Remember, it is a violation of Minnesota state law to apply phosphorus containing fertilizers to your lawn unless a soil test indicates there is a need for the nutrient or you are (re)establishing a new lawn. Additional information about this law can be found at:

3. Watering: As days get shorter, temperatures become cooler, and rainfall occurs on a somewhat regular basis, the need for additional or supplemental watering usually diminishes during the fall period. While an inch of water per week is usually necessary to keep lawns actively growing during the summer months, that same one inch of water may now be sufficient for two or even three weeks depending on weather conditions. Nonetheless, it is important to not severely drought stress a lawn if rainfall is not forthcoming. Periodic watering during the fall will help sustain active growth, allowing the grass plants to make and store food that will help it survive winter and resume healthy growth next spring.

4. Manage mowing height: Maintain mowing heights between 2.5 and 3.0 inches throughout most of the fall period. That will allow for plenty of leaf tissue to be actively involved in making food for the grass plant and a more robust root system that can take advantage of available water and nutrients in the soil. For the last two or three cuttings of the year, gradually reduce mowing heights to about 2.0 - 2.5 inches. This can help in the reduction of snow mold and allow for easier clean up of the lawn surface just prior to colder conditions arriving later in the fall.

5.Lawn aerification: If your lawn has significant compaction problems, the period right around Labor Day and through the early fall is an excellent time to do some core aerification. Lawn aerification machines are usually available through most rental businesses.
Photo 2: Lawn aerifier. Note the hollow tines for removing soil cores. Bob Mugaas.

Be sure to rent a core aerifier, one that actually pulls cores out of the soil and redeposits them on the lawn or soil surface. The extra aeration in the soil will encourage more active root growth as well as benefit the soil microbial community. Healthy plant roots and a healthy soil microbial population make for a healthy, vigorous grass plant better able to withstand stress along with normal wear and tear of lawn activity. The cores can be left on the soil or lawn surface to naturally decompose. This will also help control the buildup of thatch in the lawn. It is best to make two or three passes over the lawn to increase the number of holes needed to maximize the benefit.

6. Thatch control: Occasionally, a thick layer of brown fibrous material will build-up between the soil surface and where the grass plant shoots begin to turn green. This brown fibrous mat is known as thatch. It is actually composed of both living and non-living material. Thatch develops from the regular sloughing off of plant roots and other dead and decaying parts of the grass plant. It is however, NOT composed of any grass clippings. While there may be some grass clippings left on the surface, they are not part of the true thatch layer. So, whether you pick up your clippings or not, it will make no difference on the build-up of thatch. The living component of thatch consists of some roots, rhizomes and, of course, the many microorganisms and other living creatures.

If thatch develops at a faster rate than can be broken down by microorganisms, it can accumulate to undesirable levels. Generally, thatch greater than half-inch is undesirable. Cultural practices that contribute to thatch buildup are excessive nitrogen fertilizer, overwatering, infrequent mowing, compacted soils and simply the genetics of the particular grasses. Some grasses are more prone to thatch build-up than others.

Photo 3: Vertical mower or dethatcher; sometimes referred to as a power rake. Bob Mugaas.

Late summer (i.e., early September) is a good time to work at removing excess thatch build-up. Machines know as vertical mowers or de-thatchers can be rented and used to mechanically remove some of the thatch build-up. Leaving the soil cores on the surface will also help begin to break down thatch. In fact, where very thick thatch layers exist, using both a vertical mower and core aerifier may be helpful. If this is the case, thoroughly aerify the lawn, than perform vertical mowing. This operation can be done back to back on the same day if desired. It's a good idea to follow-up with a quarter to half-inch inch of water to reduce lawn stress incurred from the dethatching and aerification processes.

 7. Broadleaf weed control: The month of September into early October is an excellent time for controlling those pesky broadleaf perennial weeds such as dandelion and creeping Charlie. There are many different broadleaf weed control products available that can be used around the home. Always follow the product's label directions exactly as printed on the container. Remember, it is a violation of federal law to handle or use any weed killer inconsistent with its label directions.

9-09_04lawns.jpgPhoto 4: Creeping Charlie growing in a partially shaded lawn area. Bob Mugaas.

Most broadleaf weed killers work best between the temperatures of 50 degrees F and 80 degrees F. Late summer and early fall is an especially good time as these perennial broadleaf weeds are actively growing and the material is moved throughout the plant and root system, resulting in better control. While you may not see the weeds completely dying this year, chances are that few, if any, will be around come next spring.  For more information about many other common lawn and landscape weeds and how best to control them, check out the section: 'Is this Plant a Weed?', on the Gardening Information web page ( .

Fall is for Tasting and Rating University of Minnesota Apple Varieties

Excerpts from Arboretum News, Judy Hohmann, Arboretum Marketing & Public Relations Manager
Zestar in bowl high res_David Hansen.jpg
The University of Minnesota's Horticultural Research Center (HRC) breeds northern-hardy apples. Twenty-six robust varieties of apples have been introduced in the marketplace thus far. Some of these apples will be available for tasting at the Arboretum's Oswald Visitor Center (see weekend apple tasting details below).  Apples for purchase will be available at the Arboretum's AppleHouse in early fall. After 20 years of research, testing, and cultivation, SweeTango® -- the offspring of Honeycrisp and Zestar parentage will burst on the scene this year with predictions over time to jostle Honeycrisp from its superstar perch.  Look for a limited supply of SweeTango® apples for sale at the Arboretum AppleHouse in early Fall.

Photo:  Zestar apples in bowl. David Hansen.

Weekend apple tastings

Sample and rate test apple varieties - each weekend
features different apples. Drop in and complete a short survey, and
talk with Master Gardeners. Your feedback is compiled for research
scientists in the apple breeding program.
  • 1 - 3 pm on September 19 and 20, October 3 and 4; 10 and 11
  • Oswald Visitor Center, Great Hall

Arboretum AppleHouse opens

  • Tuesday, Sept. 1
  • The AppleHouse apple and garden
    market opens September 1. This is a great source for a variety of freshly picked apples
    from the trees of the Horticultural Research Center. Continues through
    October. Located at the intersection of Rolling Acres Road and State
    Highway 5, just over a mile west of the Arboretum. 

® Minneiska apple

Animal part, plant, or rare mushroom found in Anoka County?

Lynne Hagen, Master Gardener Program Coordinator, Anoka County

9-09_01Stinkhorn rare  Mushroom _Jill Libby.JPGOne never knows what curiosities can arrive in a county Master Gardener office. A phone call from a client came in with the request of identifying an object that was found in her yard. The client wasn't sure if it was an animal part, a plant or fungus. Since the person calling raised chickens and ducks, she thought perhaps it was a deformed body part but wasn't convinced. This piqued my curiosity. Upon receiving the photos, the image was forwarded a couple of Master Gardener and Extension colleagues, as well as the Bell Museum. After a little sleuthing, David McLaughlin, from the Department of Plant Biology confirmed that it was a rare stinkhorn mushroom and most likely, a Lizard's Claw Stinkhorn Mushroom, Lysurus cruciatus. He stated, "What is shown in the pictures are the stem and apical, spore-forming area. These arise from a sack-like structure in the substrate. The spores usually have a strong odor and attract beetles and flies which carry the spores away. This genus is believed to be introduced here."

Photo: Lizard's Claw Stinkhorn Mushroom, Lysurus cruciatus. Jill Libby.

Some of the information found stated that the origin is New Zealand and Australia. McLaughlin said there are only two records of this genus in Minnesota. The client that found the object saved the specimen and donated it to the Bell Museum for their collection. Anoka County continues to be full of surprises.

2009 September gardening list and tips

September 2009 gardening tips are compiled from past conversations with University of Minnesota Extension Educators through 2004, 2006, 2007 Yard and Garden News calendars, and through email conversations with Ask a Master Gardener volunteers:Barb Harlan, Theresa Rooney, Claire Kari, and Darla Medic-Johnson.

joe pye.jpg
Photo: (from left to right) Sneezeweed and Joe Pye Weed in the September garden. Karen Jeannette

While some might consider September the end of another gardening season, it might also be considered a beginning for enjoying the harvest of the garden or planning next year's activities. This time of year you may notice some central themes helpful in remembering seasonal garden and yard care tips, such as: watering, cleaning up, moving, harvesting, and preparing for next season, just to name a few. As always, this September gardening list is far from all-encompassing, yet a good reminder of where to start.


Providing adequate water in fall is especially critical for increasing plant survival in winter and providing year-round health:

  • Help your plants prepare for the long winter by adequately watering plants. This is especially true for trees and shrubs planted in the last 5 years. Provide these plants 1.0 - 1-.5 inches of water per week.. See Fall Watering advice for more information.
  • Follow this month's Lawn care checklist: late summer - early fall, (#3 out of the seven fall lawn care practice to consider)

Cleaning Up

A little clean up now can prevent a lot of weed and disease problems in the future.
  • Remove weeds and diseased plant materials from your gardens. Do not compost diseased plant materials in your home compost. For more information on other fall clean up recommendations, see Fall is Clean Up Time. 
  • Remove overripe fruits from plants or the garden so as not to encourage insects or other stray critters.

Moving plants

Harvesting & Storing

  • Apples are ripe when the starches have converted to sugars. You can feel the starch on your teeth when you bite into an unripe apple. Just because it's red doesn't mean it's ripe. If you want to become more proficient in your apple tasting abilities, see  Apple Tasting Training with host University of Minnesota apple breeder David Bedford,

Preparing for next season

Plant Information Online

Karen Jeannette, Research Fellow and Yard and Garden News Editor

Sometimes finding the right plants for your garden is half the battle of getting them planted!

The University of Minnesota's Plant Information Online database is a valuable tool for finding sources of plant materials, links to plant specific information, and much more. Created and maintained by library staff at the Minnesota Landscape Arboretum's Andersen Horticultural Library, it is updated many times a day. Kathy Allen, Andersen Library's head librarian, highlights ways that the Plant Information Online database can be used, including as a resource to find:
  • nurseries that specialize in certain plant materials (mail order)

  • where to find or buy a particular plant (mail order)

  • wholesale plant sources
  • (hint: knowing local wholesalers may provide clues about local retail plant availability)
  • nurseries or plant names (especially helpful when you can't remember the entire name)

  • plant specific links to reliable web sites with images and information

  • plant specific book and magazine citations listings
Allen and University of Minnesota Extension Librarian, Kristin Mastel, developed this 5-minute YouTube video showing how to use Plant Information Online. The video uses animation and subtitles to convey how to effectively use this online resource. Sit back and enjoy learning how you, too, can become a pro at finding plant information online!

HORT 1003 Master Gardener Core Course / Horticulture for the Home and Garden 2010 class schedule


The 2010 HORT 1003 Master Gardener Core Course / Horticulture for the Home and Garden will be held in St. Paul, Mankato, Pine City and online. While originally designed to educate new Master Gardener volunteers, this class is also open to those people who want to gain valuable horticulture knowledge without the volunteer obligation (called "ProHort"). A total of 48 hours of education, this class is taught by extension educators and faculty. Topics include: botany, soils, horticulture resources, entomology, plant pathology, herbaceous plants, trees and shrubs, indoor plants, integrated pest management, lawn care, weeds, fruits and vegetables.


2010 Class locations:

  • Online: January 12 - May 2, 2010

  • University of Minnesota - St. Paul campus: January 12 - February 6, 2010

  • Pine City, MN: January 26 - February 20, 2010

  • Mankato, MN: February 23 - March 30, 2010

2010 Class fees (includes class materials):

  • Online class: $250 for Master Gardener interns; $550 for ProHort students;

  • Face-to-Face classes (St. Paul, Pine City and Mankato): $200 for Master Gardener interns; $500 for ProHort students

Normal University fees apply for students taking the course for credit through the College for Continuing Education.

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