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Extension > Yard and Garden News > July 2015

Friday, July 24, 2015

Seeding your lawn this fall? Here are some considerations (Part 1 of 2)

Lawns in Minnesota take a beating. This is no surprise due to the extreme weather swings that we have from season to season and even within seasons. Fortunately this year has been a banner year for lawn care with plenty of rain, mild temperatures and low dew points. However, the current ten day forecast is setting us up to have some of the highest temperatures we’ve seen this summer, with dew points in the 70's. We may have another month of hot weather and then it will be time to seed bare areas in your lawn or conduct lawn renovations. With that, now is the time to start thinking about seed selection and purchasing.

Depending on the condition of your lawn and your goals going forward, I may recommend one of several renovation options and seed mixtures. Ideally, this work would be carried out from mid-August to mid-September. Renovation strategies can be grouped into four categories:

Lawn improvement- conducted when less than 20% weeds or bare soil are present. The goal is to utilize existing grass species and determine the factors leading to poor lawn quality and correct these. Often, recommended practices for improvement will include aeration, fertility, seeding, and weed control.

Partial renovation- conducted when 20-40% weeds or bare soil are present. This process requires stressing the existing vegetation to reduce the competitive advantage of existing species, while overseeding with new (possibly different) turf species. Depending on the weeds present, herbicides may or may not be recommended. 

Species conversion- conducted when greater than 40% weeds or bare soil are present, but there are no major soil issues. This process requires killing the existing vegetation by the use of non-selective herbicides or solarization (plastic sheet) and overseeding with new turf species. The species conversion process allows you to change the function of the lawn (ex: low input, no mow, high traffic tolerance) by establishing new species in a short period of time. 

Complete renovation- conducted when greater than 40% weeds or bare soil are present, and soil remediation is required. This process is essentially the same as the species conversion except soils will be tilled, graded, and possibly amended with organic matter or nutrients.

For more detailed information about all of these renovation strategies and in-depth detail on how to conduct the species conversion, view this webinar: Lawn Renovation

No matter which renovation strategy you choose, selection of the proper seed will be critical to the long term success of your lawn. I would generally suggest utilizing a mixture of several turfgrass species to overseed with, but let’s discuss the species individually and next week we’ll look at some mixtures that are available to you.

Mixtures vs. Blends

Mixtures are different from blends. Blends of grass seed include only one species, for example Kentucky bluegrass, and most blends would have 3-4 different varieties of that species. Mixtures of grass seed include two or more species and greater genetic diversity. Mixtures are often utilized for lawns that have differing microclimates (ex: sun and shade).

Cool Season Species for Minnesota Lawns

Leaf texture differences between tall fescue (left), Kentucky bluegrass (center),
and fine fescue (right)

Kentucky bluegrass is the most widely used species in Minnesota lawns due to its high aesthetic quality, adaptation and stress tolerance. If you have an existing lawn, chances are that a good majority of it is Kentucky bluegrass. Additional benefits of Kentucky bluegrass include its cold tolerance, drought survival through dormancy and high recuperative ability. However, downfalls with this species include a high water requirement, frequent mowing and high fertility needs. There is a wide range of genetic diversity in Kentucky bluegrass and Seed Research of Oregon has put together this great classification of the different varieties.

Perennial ryegrass can also be a high quality species, although its poor tolerance to winter and summer stresses make it undesirable in many cases. Perennial ryegrass is included in many of our Midwest mixtures due to its incredible germination and establishment rate. If quick establishment is desired, perennial ryegrass can be used, but I would suggest not using more than 25% perennial ryegrass in your seeding mixture.

Fine fescues have been receiving a lot of attention recently because of their ability to survive low maintenance environments. Fine fescue is a category of about five different species that are often mixed together. These species include hard fescue, slender and strong creeping red fescue, Chewings fescue, and sheep fescue. Like perennial ryegrass, the fine fescues germinate very quickly. Fine fescues are often the best performing species in drought trials and no-mow turf situations. They are also adapted to shade or full sun. For more information on fine fescues for lawns have a look at this short video: Fine fescue.

Tall fescue is a coarse fescue species that has been gaining popularity due to its shade and traffic tolerance, as well as its ability to avoid drought through an extensive root system. I find myself recommending tall fescue more and more. Tall fescue is a bunch type grass and it can be unsightly when overseeded into existing lawns, so I generally recommend using it for new seedings or utility turf areas. When tall fescue is greater than 75% of a stand it looks very comparable to a Kentucky bluegrass lawn, and it will require less inputs of water and fertilizer. Tall fescue is also very shade adapted. For more information on tall fescue have a look at this short video: Tall fescue.

For a more detailed explanation of the turf species visit this short video: Grasses for Minnesota Lawns.

Next week we will look at the various seed mixtures that are available on the consumer marketplace. Stay tuned.

Friday, July 17, 2015

Tiger swallowtail caterpillars

Jeffrey Hahn, Extension Entomologist

People have been finding tiger swallowtail caterpillars in the landscape recently. They have been on the move as they look for places to pupate. Upon first sight, this insect is quite mysterious looking. It is up to a little over two inches in length. The body is either brownish or greenish with a yellow stripe circling the body somewhat near the head.

What stands out, however, are two large yellow and blue eyespots in front of the yellow stripe. This gives the
Tiger swallowtail caterpillar. Note the
orange osmeterium near the head and
the yellow and blue eyespots.  Photo:
Howard Ensign Evans, CSU State Univ.
caterpillar a rather menacing appearance. To further enhance this threatening look, the caterpillar can swing its head from side to side, mimicking a snake. And if that was not enough to keep someone at bay, it can evert a forked structure called an osmeterium near the head. This structure can not only startle someone but can also emit a foul odor to help protect the caterpillar.

Despite all of its bluster, a tiger swallowtail caterpillar is perfectly harmless to people. Don’t be alarmed if you see one, just let it go on its way and know it will grow to be a beautiful tiger swallowtail butterfly.

To see more pictures, see the eastern tiger swallowtail entry in BugGuide

Cedar Apple, Quince and Hawthorn Rust

M. Grabowski, UMN Extension Educator

Cedar apple rust on Zestar apple, M Grabowski UMN Extension
Several rust fungi are now showing up in brilliant colors on hawthorn, apple, crabapple and other trees and shrubs in the Rosaceae family. Infected leaves have bright orange, yellow or red spots. Infected fruit are covered with small tube like fungal structures, that pour out large quantities of powdery orange fungal spores. Cedar apple rust, hawthorn rust and quince rust are all caused by fungi in the genus Gymnosporangium. The Gymnosporangium rust fungi infect juniper for half of their life cycle. On cool wet spring days gelatinous bright orange spores can be found on galls or cankers on juniper trees. Those spores cause the infections on trees and shrubs in the Rosaceae family. In turn spores produced by the Rosaceae trees and shrubs will infect junipers.

Quince Rust on Hawthorn Fruit, M. Grabowski UMN Extension
As a result of this unique life cycle, leaf spots may grow slightly bigger, but no new leaf spots or fruit infections will form this year on the Rosaceae trees and shrubs. The Gymnosporangium rust fungi rarely cause damage to the health of  trees and shrubs in Minnesota. So enjoy the colors and unique biology of these interesting fungi. No management is needed.

Garlic Rust

M. Grabowski, UMN Extension Educator

Orange and black elliptical spots on garlic leaves and stems are signs of garlic rust. Cause by the fungus Puccinia allii, garlic rust can infect several members of the allium family including garlic, onion, chives and leeks. Severe infection can result in yellow, withered leaves and reduced bulb size. Not much is known about the biology of the garlic rust fungus. Infection occurs in cool moist conditions and two different types of spores are commonly found on infected plants. The orange spots produce urediniospores. These are easily spread from plant to plant during the growing season resulting in new leaf spots. The black spots produce teliospores. These tough spores survive in plant debris and start new infections the following growing season.

If garlic rust appears in the garden, remove all leaf and stem debris from the garden after harvest. These infected leaves and stems can be burned, buried in an area where no alliums will be grown or composted in a pile that heats up. If backyard composting is not available many areas offer municipal compost drop off sites. Avoid planting garlic, onions, leeks or chives in the same area for the next 2-3 years. It is not known if the garlic rust fungus can move from an infected plant into the garlic cloves used for seed, but disease originating from infected seed has never been reported.

Japanese beetle management options

Jeffrey Hahn, Extension Entomologist

Japanese beetles are being found in gardens and yards now. Although the first discovery of these pests was recorded on June, 18, it hasn’t been until more recently that they have become more abundant. Japanese beetles are challenging to deal with, especially when they are numerous. The following are non-chemical and chemical options for managing them.
Japanese beetles having their way with a grape leave.
Photo: Jeffrey Hahn, UMN Extension

A good non-chemical method is physical removal. To be effective, it should be done every day (or at least as regularly as possible). If you can only handpick these pests once a day, research shows the best time to do so is during early evening. Have a container of soapy water with you so that beetles that are brushed or picked off the plants end up in the water where they are killed.

For smaller plants, consider using a fabric barrier, like cheesecloth. The fabric is placed around the plants, preventing the Japanese beetles from getting at them. You can make your own or buy them from a garden store or online site that sells garden supplies (e.g. Gardens Alive). The fabric should be lightweight and allows light and rain in. Be sure to take the fabric off of any plants that are flowering so bees can reach them.

One non-chemical method to avoid is traps. Although they are popular and can capture an impressive number of beetles, what are found in the traps is actually just a small number compared to how many Japanese beetles are actually out there. Research from the University of Kentucky has shown that these traps actually attract more Japanese beetles than they capture; plants in these areas often suffer more damage than they would have without the traps.

If you are interested in using an insecticide, consider a low impact product like Neem. Neem does not actually kill them, but causes them to stop feeding. While this can be effective on small to medium numbers of beetles, it is less effective against large numbers. Another option is pyrethrins (containing piperonyl butoxide). Pyrethrins do not contain any residual; it is only effective on what it directly contacts and repeat applications are likely necessary.

If you would like to use a product with a longer residual, consider a pyrethroid, such as permethrin, bifenthrin, lambda cyhalothrin, or cyfluthrin. Another option is carbaryl (Sevin). Depending on the Japanese
Japanese beetles on basil.  Be sure to check to insecticide
the label to be sure the plants you wish to treat are listed.
Photo: Michelle Grabowski, UMN Extension
beetle numbers, you may need to make more than one application. Be careful not to apply one of these insecticides when bees are active.

Another option is the use of imidacloprid, a type of systemic insecticide (dinotefuran is a similar systemic insecticide but is less effective against Japanese beetles). It’s easy to apply and is long lasting so only one application during the summer is necessary. It does not kill Japanese beetles quickly but it does cause them to stop feeding, then they die a little later. It is important to note that this product is very toxic to bees. Avoid treating flowering plants (or plants that may still flower later this summer) that are attractive to bees.

When applying insecticides, be sure that the plant you wish to treat is listed on the insecticide label. This is especially important when treating fruits and vegetables. If the plant you wish to treat is not on the label, then do not make an application to it. Instead, find a product that is cleared for the plants you are trying to protect.

Friday, July 10, 2015

Mints - friend or foe?

Mint plant
Rhizomatous roots and creeping stems

Mints have square stems.
 Plants in the Mint family have a well-know reputation for being aggressive. Some, like creeping Charlie Glechoma hederacea) are common pests for many homeowners and gardeners. Wild mint (Mentha arvensis) is a Minnesota wildflower.

Mints can most easily be identified by their square stem and fragrant leaves when crushed. Mints are aggressive and have rhizomatous root systems and creeping above-ground stems, making them difficult to eradicate. Mints grow well in sun and shade, and are adaptable to various soils. Many mints are grown for culinary use, and mints - including creeping Charlie - are good sources of nectar for pollinators. Still, some people want to eliminate large areas of wild mint (and creeping Charlie) from their landscape. There are essentially three options: (1) treating the area with a broadleaf herbicide with glyphosate + triclopyr. (2) Solarization using clear plastic sheeting. (3) Dig out the plants, removing as much of the plant root as possible.

(1) Spraying a broadleaf herbicide would be the fastest option. However, the broadleaf herbicides noted above are non-selective and will most likely kill every plant. So it is important to treat the area on a calm day (no wind) and to protect desirable plants with mechanical barriers such as cardboard pieces / boxes, leaf bags, tarps, etc. These should be left in place till the sprayed foliage is dry. Always follow the instructions for proper chemical use, storage and disposal on the product label.

(2) Option two is solarization. Plants are cut back and sheets of clear plastic (not black) are laid down tightly over the plants. Solar energy will heat up and kill the plants and seeds. The plastic should stay in place until plants have died back completely. According to the University of California IPM website, this may take 4-6 weeks depending on the intensity of the sun's energy, number of sunny days, and the plants' resiliency.
(3) Option three- and most labor intensive - is digging out the mint. Because mint can vegetatively propagate - grow from a small piece of root or stem - it is important to dig out as much of the root as possible and resist pulling the plants out thus breaking the roots. Digging out the plants could be done in conjunction with Option one or two as well.

After eradicating the mint, it is important to follow up regular weeding and treatment as necessary. If re-establishing lawn, choose grass seed appropriate for the site and re-seed as per Lawn Renovation. For landscape beds, mulch the area with 2-3" of wood mulch and / or replant with preferable plants. See Extension publication Mulching the Home Landscape. Typically, landscape fabric is not recommended nor is it necessary; however, because the goal is to prevent a perennial from re-sprouting, fabric is an option under the wood mulch.

From eXtension Ask an Expert: 'William Baffin' Rose

Rosa 'William Baffin' supported by a trellis,
at the MN Landscape Arboretum
Q: I have a 'William Baffin' rose bush growing in the lawn area of my landscape. It has well over 50 hips forming after a really fabulous bloom. Do I cut them off now or leave them on the plant? Will the rose re-bloom? 

A: 'William Baffin' is a repeat climbing rose; that is, it most likely will set more buds and bloom till frost. Pruning off the early hips will encourage the plant to put more energy into blooming rather than setting seed (the hips). You may decide to leave the later season hips on the plant as winter interest.

As a "climbing rose", 'William Baffin' requires
 support. Unsupported, it is a sprawling rose. Often climbing roses are trained along arbors, walls, fences, etc. Provide a strong trellis and tie the canes along the trellis. This will support the plant and allow light to reach the canes, improving plant health and bloom. Use a soft / padded tie material to avoid girdling the stems. You can purchase various types of covered wire and tie material in garden centers and online or use nylon stockings cut into 5-6" lengths.

Rosa 'William Baffin' is a repeat bloomer.
You note that the rose is growing in a lawn area. Grass will compete for light, water and nutrients, and the rose, as it grows, will shade out the grass, allowing for weeds to grow. It is best to remove the grass now by digging it / pulling it out in a 3-4' diameter circle around the plant. Apply rose fertilizer to the bare soil (always read and follow the directions on the label). Then mulch the plant with wood mulch about 2"-3" deep, pulling the mulch away from the main stem 3" to allow air and light to reach that area of the plant. Note that as wood mulch decomposes, it absorbs nitrogen from the soil, so the rose fertilizer is helpful in maintaining plant health through the season. No landscape fabric is needed under wood mulch. Mulch will conserve moisture, suppress weeds, protect the rose, and will show off the plant much better than grass. 

Do you have a gardening question? Extension educators and Master Gardener volunteers are ready to help:

Thursday, July 9, 2015

Anthracnose Blights Shade Trees

M. Grabowski, UMN Extension Educator

Anthracnose, a fungal leaf blight of several different shade trees, is not uncommon in Minnesota. This disease causes brown spots and cupping or distortion of young leaves. The fungal pathogens that cause anthracnose thrive in cool wet weather common in early spring. In a typical year, trees recover from anthracnose as summer brings hot dry weather and leaves become naturally more disease resistant as they mature.

This year several cases of severe anthracnose have been reported in late June and July; later than usual. Maple trees with advanced cases of anthracnose have large brown blotches on fully expanded leaves. In white oaks, the typical anthracnose leaf symptoms can progress to shoot blight. In the shoot blight stage of anthracnose, several leaves turn completely brown along with the young shoot, resulting in clumps of dead leaves at the ends of branches. These leaves may remain attached for the entire growing season and into the next. As a result clumps of dead leaves seen this year may be a result of last year's infection.

The unusual timing and severity of symptoms observed from anthracnose of shade trees this year could easily be confused with damage from other pests, pathogens or abiotic causes. The cause of the problem must be properly identified before an effective management decision can be made. For assistance in diagnosing plant problems, samples can be sent to the University of Minnesota Plant Diagnostic Clinic

Anthracnose is a minor stress on the tree and will not significantly affect the health of the tree unless the majority of the canopy is affected several years in a row. There is no treatment effective against anthracnose that can be applied at this time of year.
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