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.

Hypoxylon canker

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

Overflowing entrance sign at Oak Ridge

We are proud to announce that Field Outdoor Spaces was awarded a 2010 MNLA Merit Award for our annual bedding plant management and garden maintenance at Oakridge Golf Club located in Hopkins, MN. We are going on our fifth year of partnership installing and maintaining the club’s annual flower beds. This is the second year in a row that we have won an award for commercial garden maintenance.

Last fall, we submitted our entry for the landscape management award to MNLA (Minnesota Nursery and Landscape Association). Part of the award criteria was based on the submission of twenty digital photos taken throughout the season and a written description about each photo. Please visit the website www.gardenminnesota.com to check out our work under ‘Award Winning Landscapes’ and ‘Merit Award 2010.’ Pictures of the gardens will also be displayed through March at the Minnesota Landscape Arboretum in Chaska, MN.

Hole 10 annual combination

Preparation for the annual installation begins in January with new designs and preparing the plant order. Around May 15^th, our crews install the annuals. Colorful seasonal plantings are found in high traffic areas with bold bursts of color that greet club members. Our annuals are found around the tee boxes, under trees, and in areas where members and their families frequent, such as the pool and tennis court areas. In a typical year we install over 250 flats of annuals at the club, including simple bedding plants like zinnias and petunias as well as specialty plants like cannas, purple fountain grass and house ferns. After installation, we are at the course every Monday to dead-head, remove dead or underperforming plants, and weed every week.

We are honored to have won such a distinguished award. Our company, along with other award winners, will be recognized at a dinner hosted by MNLA in March.

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:

(from Colorado State website)

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.

Watering trees is incredibly important. The drought this summer has left a huge number of our boulevard trees looking like this.

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

:

'White Swan' Echinacea with aster yellows. These are actually leaves growing into the flower head.

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

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.