by Ann Davenport

Quaking Aspen (Populus tremuloides) has become a staple in many northern landscapes. We love its straight form, smooth gray-green bark, and the way its leaves quiver in the wind. Its strong presence is able to bring a little bit of the north woods to our urban landscapes. Sometimes despite our best efforts, pests and or disease can put a blemish on our otherwise well manicured space.
The U.S. Department of Agriculture Forest Service has categorized Hypoxylon Canker, caused by the fungus Entoleuca mammata, as one of the most important diseases affecting Aspen in our area (Anderson, R., Anderson, G., & Schipper, A., 1997). The fungus enters the tree through wounds in the bark. Wounds can occur through insect damage or mechanical damage (pruning, mowers, etc…). Initial infections often occur in small branches. With age, the infection moves into the main stem of the tree. Unfortunately, the prognosis for trees infected with Hypoxylon Canker is grim. Once the cankered area reaches the main trunk it will girdle the tree. Most trees that reach this stage will die within five years.

Here are some things to look for when monitoring Aspen for signs of infection:
• Leaves on the infected branch(s) appear smaller than normal, turn yellow, then brown
• Cankers usually begin near wounds, branch stubs, or at the base of branches
• New infections are marked by sunken bark which is initially yellowish-orange, turning black at the center with yellowish-orange margins as the infection ages
• During early infection, the bark of the canker has a blistered appearance
• With time, the blistered area breaks apart and falls off revealing blackened wood
Unfortunately, there is no chemical treatment for Hypoxylon Canker. Trees with main trunk infections should be removed to prevent further spread to nearby Aspen. Routine monitoring of trees in the landscape can help identify early signs of the disease. Removal of infected braches before the cankered area reaches the main trunk may delay infection. This should be done during dry periods to minimize spread of the fungus. In general, pruning cuts should only be made when necessary and sterilization of equipment between cuts is recommended to minimize risk of spread. The best way to protect your Aspen from this disease is to provide an environment that encourages tree vigor; appropriate fertilization, and adequate water to prevent drought stress.

Source:
Anderson, R., & Anderson, G., (1997). Hypoxylon Canker of Aspen. U.S. Department of Agriculture Forest Service. Forest Insect & Disease Leaflet 6. Retrieved August 1, 2010 from http://na.fs.fed.us/spfo/pubs/fidls/hypoxylon/hypoxylon.htm

Do you have that itch to get out in your garden yet?  I know your garden is filled with snow and that it is falling as I type, but there are some things you can do right now to get your garden off to a great start for the 2010 landscaping season.

Deciduous trees and shrubs need regular pruning than other plants, but fortunately, it is relatively easy.  Dormant pruning is done to produce strong, healthy, and attractive plants that are safe to be around.  Proper procedures should begin when the plants are young to produce a strong structure and to eliminate potential problems when plants are young and small.  Listed below are a few reasons to prune:

 Safety

• Eliminate dead or dying branches that are injured by disease
• Remove branches that cross and rub against each other

 Aesthetics

• Encourage flowers and fruit
• Shape limbs that could damage people or property
• Eradicate branches that have poor angles resulting in their susceptibility to snapping in high winds or ice
• Eliminate branches that obscure intersections or cross with power lines

 Plant Health

• Shape, i.e. a hedge
• Control size
• Remove suckers and water sprouts

Trees and shrubs that bloom later in the growing season should be pruned when they are leafless and dormant, just before the new growth begins for the season.  This is typically in February when new tissue develops rapidly in response to spring.  Another reason to dormant prune is to see the overall architecture of the plant you want to prune.  The leaves aren’t there to muddle your views.  Dormant pruning also prevents the spread of oak wilt disease.  It is a disease that is dispersed by spores between the months of April to June.  Do NOT prune an oak tree during these months.

One exception to dormant pruning involves trees such as maples and birches.  The tendency for them to bleed in the early spring can be unsightly.  It is best to prune those types of trees well after the trees have leafed out in the summer.  Below is a diagram depicting a proper pruning cut on a tree:

 

There are two primary pruning methods, renewal and rejuvenation. Renewal pruning cuts out older stems near the base.  This stimulates the growth of younger stems and keeps the shrub flowering and fruiting.  Subsequent pruning may need to occur to maintain the shape of the shrub.  Understanding the natural shape of shrubs will help you determine how to prune.  Shrubs that respond well to renewal pruning include lilacs, red twig and yellow twig dogwood, some species of viburnum, forsythia, mockorange, and weigela.  Most of these shrubs are pruned within two weeks after they flower in the spring. 

The second type of pruning, called rejuvenation pruning, involves cutting stems down to the ground. This method is useful when a shrub has become overgrown with many stems growing together. Some shrubs that respond well to rejuvenation pruning include Anthony Waterer spirea, honeysuckle, snowberry, and privet. Early spring is the best time to initiate this type of pruning.  There is a rejuvenation program that takes three years to complete but the overall attractiveness of the plant is maintained.

Year 1: Remove 1/3 of the oldest canes that are not productive anymore. 

Year 2: Remove one half of the old stems. 

Year 3: Remove the remaining old branches.  New stems will quickly grow to fill in where the old wood was thus creating a more lush plant.

 

A lot of cuts are made on suckers which are vigorous vertical stems that are unsightly. The best way to get rid of suckers is to rip them out of the ground early in the spring while the stems are still small.  Opposed to pruning, this method removes the bud and will discourage the growth of new suckers. 

Finally, recent studies have shown that applying a paint or wound dressing to the cut will not prevent decay like it was previously thought.  The tree or shrub will form a callus on its own that will close over the wound and protect itself.  You also need to disinfect cuts between each cut with a product such as Lysol.  This will prevent passing diseases on to the next plant.

With these pruning tips and methods you will be armed with the knowledge to make thoughtful and decisive pruning cuts in your landscape.  Remember that if you make a mistake, you can always try again next year.

This is the season to get to your local garden center and start to plant!  There are so many fabulous sales going on right now and this is a great time of year to get back in your garden and plant.  It’s just a warning, but frost will arrive this month.  The question is when and how hard will it hit?

• Divide and transplant plants such as iris, daylilies and hostas
• Plant peonies now, but make sure the crowns are buried only one and a half to two inches below ground level. Planting them deeper than two inches may keep them from blooming.
• Perennial phlox can be divided about every third or fourth year. Divide big clumps of perennial phlox into thirds. Early fall or early spring are the best times to plant or transplant them.
• Purchase plants and get them in the ground so their roots can become established before winter. Replace any plants that did not survive the summer and fill in the spaces in your garden.
• Prune arborvitae bushes
• Keep weeding
• Destroy any yard waste that is diseased
• Rake up leaves, twigs and fruit from crabapple trees and dispose of them in the trash to help control apple scab disease.
• Fall is a good time for improving your garden soil. Add manure, compost and leaves to increase the organic matter content.
• Be sure to keep strawberry beds weed free. Every weed you pull now will help make weeding much easier next spring.
• Keep watering. It’s important to provide adequate moisture going into winter to help prevent winter damage.
• Select accent plants for your landscape that will provide autumn colors. Trees that have red fall color are flowering dogwood, red maple, sugar maple, Norway maple, red oak and scarlet oak. Shrubs with red fall foliage include sumac, viburnum, burning bush and barberry.
• Stop fertilizing plants so plants can begin to rest before shutting down for winter
• After a hard freeze, dig up dahlia and canna tubers and store in a cool place inside for the winter
• Later in the month, plant tulips, daffodils, and other spring flowering bulbs
• Plant grass seed and be sure to keep watered
• Harvest the last of the vegetables and herbs

Text by Carolyn Johnson

by Carolyn

:

August happenings in the garden

 

• If planting in August, keep plants well watered
• Cut back ‘tired’ plants
• Weed
• Stake plants as needed
• Do not fertilize perennials, roses, or shrubs after August 1; they need to prepare for winter. However, it is a good time to apply fertilizer to your lawn.
• Watch for grasshoppers and aphids in the garden
• Deadhead daylilies and other perennials
• Plan for your fall garden
• Cut back any disease or insect damaged foliage
• Divide iris and peonies
• Lawns can benefit from core aeration, especially if you have high foot traffic areas or clay soil
• Harvest fruits and vegetables from your own garden or take advantage of your local farmer’s market.

Sources:

http://www.arboretum.umn.edu/augustgardeningtips.aspx

“The Well-Tended Perennial Garden” by Tracy DiSabato-Aust

July To-Do List

• Sharpen mower blades to prevent grass from tearing and causing damage to the blades
• Mow high and mow less often since we usually don’t get as much rain this time of year
• Keep planting to a minimum this month unless you know you can water religiously
• Prune spring bulb foliage back
• Keep new plants moist with deep and infrequent watering
• Perennials that have been pruned must be kept moist
• Keep on top of weeding
• Watch out for plants that need to be staked
• Look for Japanese beetles and other insects. If using pesticides, be sure to read the labels.
• De-leaf early blooming plants to keep up their appearance
• Deadhead perennials to keep them blooming
• Apply mulch around plants to conserve water
• If you want beets, turnips, and cole crops such as brussels sprouts and broccoli plant them now
• Renovate strawberry beds after harvest
• Turn over the compost pile

 

 

 

The Japanese Beetle can be one of the most destructive garden pests, especially on roses, raspberries and linden trees. Late June to the end of July are the prime foliage eating times for the Japanese Beetle adults and one of our clients has spotted them in her garden already.

The Ohio State Extension Fact Sheet lists several options to control or minimize Japanese Beetle damage… these are the two that make the most sense:

Option 1: Cultural Control - Hand Picking

The first Japanese Beetles that arrive in your garden are often “scouts.” They chemically signal other Japanese Beetles to join them at the feast. By noticing when the first adults arrive on a property, you can pick off and destroy these scouts that attract additional pests. The adults are less active in the early morning or late evening. They can be destroyed by dropping into a container of soapy water.

Option 2: Insecticide

The adults can be controlled by spraying susceptible plants with insecticides. Over-the-counter pesticides available for this include: acephate (Orthene), carbaryl (Sevin), and several pyrethroids - bifenthrin, cyfluthrin, deltamethrin, lambda-cyhalothrin, permethrin, and others. Applications of imidacloprid (=Bayer Advanced Tree & Shrub Concentrate) generally need to be made 20 days before anticipated Japanese beetle adult activity. During the heavy adult activity periods, sprays may be needed every 5 to 10 days.

A couple of important notes - there is no “Japanese Beetle” specific insecticide, so the insecticides will kill other insects in the process, some of which may be beneficial in your garden. Also, there is a Japanese Beetle look alike called the False Japanese Beetle. It is more greenish black in color and will not have the distinctive 5 hairy stripes on the side that the Japanese Beetle has.

Living “cheek to jowl” as we do in our neighborhoods always develops the potential for some neighborly disputes. None is more contentious than the “fence vs. privacy” dispute. In some neighborhoods it is considered un-neighborly to put up a privacy fence. In the cozy St. Louis Park neighborhood in which my inlaws live, it is well understood (and enforced) that no one will ruin the rolling sward of forest and lawn by imposing fences. Even in Minneapolis, we encounter many, many hard-feelings and bitterness that are the result of someone putting up a fence.

On the otherhand, the need for privacy is a central factor in our client’s decision to call in a landscape designer. Even when we like our neighbors, we don’t want to always have to step out the door and be intimate with their every gathering and impulse. To say nothing about the neighbors who have a barbeque party every night and can only talk at the highest decibels. Or the nice family who’s children stare through the chainlink fence and ask you questions about everything you do. Or the mechanic who uses his yard as a storing area for various car carcasses and greasy parts. Even the “Master Gardener” neighbor who has such a carefully primped front yard always has a tendency to pile all her clay and plastic pots and compost pile along our property line to stare at all winter.

Here are a few rules when thinking about fences and privacy:

1. Think about your neighbor’s perspective during the design process (and beyond). What effect will the fence (or other privacy measure) have on their space? What ways can the design not only decrease the negative effects of the measure, but hopefully be an asset for them as well.

2. While I do not recommend having a “blank slate” brainstorming conversation with you neighbors, I do recommend that you talk with your neighbors about your intentions. Discuss not only the decisions you’ve made but what led you to the decision. Be sure to mention ways in which you’ve considered their space. Ask them what they think and if there is anything they feel strongly about. Sometimes their input can lead to a solution that is better for all parties.

3. Make the fence as transparent as possible while gaining the privacy required. No one wants to feel like they’re in a walled prison. Focus on blocking out the elements that require blocking, while leaving open views, areas for sun exposure, and paths for air circulation. Good fence design has a “light touch,” still leaving the space feeling open and with circulation and flow.

4. When using plants for privacy, be cautious about overusing evergreens. In our climate, evergreens are prone to burn and other issues that can make them look mangy and worn. Mixing evergreens and deciduous shrubs and tiering plantings in front of them, will often provide the privacy required without making it look like an obvious “wall.”

5. Get a survey done and double-check the city rules on fence locations. A survey seems like a hard pill to swallow at the time - they seem to run $600-$1000 - but they can save a lot of pain in the long run.

June To-Do List
• Try to finish planting by early this month
• Transplant and divide perennials; keep watered and shaded
• Start to place stakes around plants that need it
• Watch for Japanese Beetles
• Deadhead to extend bloom times of perennials
• If it has rained, wait to get into the garden until after soil has dried to prevent spreading fungus and disease
• Start perennial seeds now so they will have a strong root system before winter
• Take photos and notes of what looks good and what doesn’t so you can have records to work with when planning next year’s garden during the winter month
Pruning:
• Cut leaves from spring flowering bulbs once they have faded
• Prune spring flowering shrubs, like lilacs and forsythia to help promote new growth
• Cut back spring-flowering plants
• Pinch autumn-flowering plants
• Shear any foliage that is showing signs of distress
In the vegetable garden:
• Plant heat tolerant types of lettuce that can be shaded by other crops
• Plant short-season crops now so they will ripen before frost
• Remove crowded seedlings to make room for the stronger plants
• Donate extra veggies to a shelter or food bank

Sources: The Well Tended Perennial Garden, Tracy DiSabato-Aust, http://www.nwhealth.edu/healthyU/getMoving/garden3.html

This weekend we saw the first saw fly larvae on a pine tree. Double-check your pines for this pesky pest - they are tiny worm-like larvae of the saw fly and their voracious appetites can defoliate even large trees. You can spray the tiny monsters off with a garden hose or, on larger trees, call your friendly arborist for control measures.

May To-Do List

• Remove plants from their pots and untangle any roots before transplanting to your garden.
• Wait until mid-month to plant tomatoes, since frost is typically gone after May 20
• You can plant annuals after the last frost. But be sure to put them in containers or in well-drained garden soil - spaced evenly apart. Water only the soil and not the leaves. If you see any leaves with spots on them, be sure to remove them immediately.
• Postpone major pruning of trees and shrubs until next winter (unless they are broken).
• The last two weeks in May is the peak time for planting annual and tropical flowers.