Once again this year Tree Trust will be partnering with the cities of Minneapolis and St. Louis Park to provide low cost trees to residents.  For every new tree that is planted each year, five are lost to storms, disease, and pests.  With the increasing presence of Emerald Ash Borer in our area, it’s so important to start re-canopying our urban forest today!  This is a great opportunity to add a tree to your existing landscape and at an unbelievably low cost .  Additional information about the sale, including the tree varieties available in each city, can be found by visiting Tree Trust.  The trees have sold out in the past so don’t hesitate to take advantage of this great opportunity!

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By Ann Davenport

Well, the consensus is in (by consensus I mean a poll of those of us working in the office this winter—very official I know) and it seems that we are experiencing a drought here in Minnesota.  Just to confirm my suspicions, I checked in with the folks over at the University of Minnesota and my favorite climatologist, Mark Seeley, to see what they were saying about our unusual winter.  Yep—It’s dry and strangely warm….but for more detailed, not to mention interesting information about our Minnesota climate, check out their cool climatology website.

I know that we’ve all enjoyed this warm weather and I certainly haven’t been sad to not be shoveling snow every other minute but the big question looming out there is what does this mean for our gardens????  Here are a few things that I’ve been thinking about.

I think one of the biggest concerns is drought stress on trees and shrubs.  We experienced a warm, extended fall and hopefully everyone took advantage of it and kept watering their trees and shrubs up until the very last possible moment.  Providing supplemental water going into winter (drought or not) is one of the best ways to arm your trees and shrubs against our harsh winter elements.  In our area, the ground is now frozen anywhere from 4-8” in depth.  Providing additional water at this point likely won’t help your plants too much, as more is likely to run off than be absorbed.  If you do choose to try providing a little more water at this point, make sure to add it very slowly in order to minimize runoff and maximize the amount available to the plant.  It’s also not too late to burlap any newly planted evergreens which haven’t had a year or two to become established in the garden.  Evergreens are very susceptible to winter burn, caused by a drying out of their needles by the wind.  Only time will tell what kind of spring is in store for us but if the drought continues, getting an early start on watering may be necessary once the ground thaws and the new growth begins to appear.

This winter’s lack of snow is another potential issue for the gardens.  Snow acts as an insulator for our plants.  It helps keep the ground frozen when we experience temperature fluctuations.  It prevents heaving as the moisture in the soil expands and contracts, and also provides extra protection for tender perennials.  Most of our Zone 4 plants should be able to withstand a winter with little to no snow cover but it is possible that we’ll see more dieback on things this year.

The warmer than normal temperatures may also impact the number of pests we see in the garden.  The mild winter may help larger populations of insects whose numbers normally would be diminished by cold winter temperatures survive.  Winter certainly isn’t over yet and I wouldn’t be surprised at all to find that we still experience some bitterly cold days but will it be enough?

It’s easy to think that all this is doom and gloom for the garden but when I look out at my snow-less landscape, I’m intrigued, amazed, and very excited to see what spring will bring.  Plants can be so resilient.  They’ve been “going with the flow” forever.  It’s us who have a hard time changing.  Yes, maybe not all of my plants will make it this year.  Of course I’ll be sad for the ones that don’t.  But at the same time, I see it as an opportunity to try something new and what gardener isn’t thrilled with the prospect of that!

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The calendar has turned to September and the air is getting cooler.  It’s easy to think that your “work” in the garden is done but don’t put those hoses away yet!!!  Providing adequate water into the fall is a critical piece in assisting plants to prepare for our tough, Minnesota winters.  Continuing to water until the ground freezes increases plant survival as well as improving year round plant health.  Although Mother Nature often helps us out with rain in the fall, sometimes you will need to do a little supplementing to ensuring that your plants get 1-1.5 inches of water every seven to ten days.  With that said, it’s important not to over water.  Over watering can cause plants to send out new growth resulting in tissue that won’t be hardened off for winter.  It also can simply result in too much moisture in the ground, causing the roots to rot.  This is especially true in heavy, clay soils.

All of the plants in your landscape will benefit from fall watering, but it is especially beneficial to evergreens as well as trees and shrubs planted with in the last five years.  Because plant roots cannot extract water from the frozen soil, helping them to be retain moisture in the fall will help prepare them to survive whatever Old Man Winter throws their way!  So keep an eye on the weather and make sure your landscape gets that 1-1.5 inches of water per week.  Next season your plants will thank you for it.

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By Ann Davenport

May and June is the time to get out into your garden and take a look at your pine trees.  Do they look like they are losing their needles?  Take a closer look.  Do you see little worms on the old needles?  If so, you are likely looking at European Pine Sawfly.  European Pine Sawfly are part of the wasp family.  It is the larvae stage that eats your pine needles.  The larvae are about an inch long with a black head and a gray-green body.

They feed in groups on the previous year’s needles.  Mugo, Scotch, Jack, and Red pine are favored by European Sawfly.  White and Austrian pine are less susceptible.

Early detection is the best method of control for the European Pine Sawfly.  Begin inspecting your evergreens in early May for signs of feeding.  If caught early, they can easily be removed by hand.  You can blast them off with a hose or spray with an insecticidal soap (you can purchase it or make your own with liquid dish soap).  You may need to spray a couple times a week during the feeding season.  As larvae mature, insecticidal soap becomes less effective and you may need to step up to an insecticide containing pyrethrin.  This can be found at a hardware store or garden center.

To make your pines happier and healthier and less attractive to sawfly, water them regularly throughout the summer and up to the first frost.  One to two defoliations won’t kill an otherwise healthy pine.  The new growth isn’t affected and barring no other disease or insect factors, the plant should recover.

For additional information about European Pine Sawfly as well as other Sawfly species found in Minnesota take a look at this University of Minnesota Extension publication.

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By Ann Davenport

I love a good Pagoda Dogwood (Cornus alternifolia).  Its defined shape adds an element of architecture to the garden.  White flowers and bluish berries on red stems provide multiple season interest in our outdoor world.  Sadly, this great shrub/small tree is susceptible to a disease know as golden canker.  Upon first look, infected branches are a not entirely unpleasant orange-yellow color in contrast to the dark reddish-purple healthy bark.  A closer look at the yellow branch will reveal hundreds of tiny, blister-like orange spots.  A distinct line marks the area between healthy and diseased tissue.  Any branch that has turned completely yellow is dead and will not leaf out.

Golden Canker is caused by the fungus Cryptodiaporthe corni.  Very little is known about this fungus other than that it only affects Pagoda Dogwoods, especially those which are heat and drought stressed.

It advances within the plant while the plant is dormant.  Any branch that is completely encircled by the fungus will die and if the fungus reaches the main stem of the plant, the entire canopy may die.

If you have a Pagoda Dogwood in your landscape, there are several things that can be done to either reduce the risk of acquiring golden canker or help control the disease in already infected plants.  It is important to visually inspect the dogwood in the spring before new growth begins.  Any infected branches should be removed several inches below where the infected bark meets the healthy bark.  The fungus travels in advance of that “dead” line so cutting farther back into healthy tissue increases the chance of removing all of the infected tissue.

It is also important to sterilize your cutting tool between cuts so as not to transfer fungal spores to uninfected tissue.  Any infected branches should be disposed of (not composted) and removed from the area.

Providing optimum growing conditions for the plant can reduce the chances of it becoming infected.  Pagoda Dogwood is native to our region and is typically found as a small understory tree, preferring shaded to partially shaded areas.  Providing a similar environment in the home landscape will help reduce stress to the plant.  Also, mulching around the base of the plant will help keep roots cool and retain needed moisture.  During dry periods supplemental water should be provided.

With a little bit of care and a few extra steps, pagoda dogwoods can thrive in our landscapes.  They add a unique quality that is difficult to replicate and well worth that little bit of extra time.

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By Jason Rathe

The cities of Minneapolis & St. Louis Park, through the organization Tree Trust, are currently offering low-priced trees for residents. Although it looks like many are sold out we decided to put together a list of our favorite trees for urban lots (many of our favorites are offered – like blue beech, serviceberry, ironwood, oak, crab, and Kentucky Coffee). The trees are broken down into the top three based on critical categories: large trees, medium trees, small flowering trees and shade trees.

Seed Pods on a Kentucy Coffee Tree

Large Trees: Large trees are the cornerstone of our urban forest. They provide shade and energy savings for our houses and many supply critical habitat and food sources for gads of critters – from insects on up.
Oaks – Whether red, burr or white. Oaks are our region’s most majestic trees. In the book Bringing Nature Home, author Douglas Tallamy lists oaks as the most important plant in supplying habitat, food and pollen for insects. Burr oak and white oak are slow growing but red oak and swamp white oak have a medium growth rate. White and burr oaks are two of the longest lived trees in our neighborhoods. If you haven’t noticed the amazing burr oak arching over Lyndale Ave. around 45th St., take a look when you are in the neighborhood.
Kentucky Coffee Tree – This native tree is a great tree for tough spots. It is used more and more as a parking lot tree. The tree has an open habit with interesting, furrowed bark, and thick, dark pods that offer winter interest. The fine leaves turn yellow in the fall. Like oaks, it is fairly slow growing. If you ever go to the Mill City Cafe in N.E. Minneapolis, take note of the great Kentucky Coffee Tree near the steps – it was only planted 10 years ago and already has great stature.

Fall "Fruit" of the Ironwood

Maples – Our native red maple and sugar maple make nice urban trees, either in their native species form or in popular cultivars like “Autumn Radiance” red maple or “Fall Fiesta” sugar maple. They both have medium growth rate and spectacular fall color. They won’t thrive on the boulevard or other exposed and droughty areas. This is a tree to keep well watered, particularly during establishment. (We recommend these over the crazily popular “Autumn Blaze” maple or any of the Norway Maple cultivars).

Medium Trees: Medium growth rate trees are some of the most versatile trees for our urban landscapes. The size gives nice shade without the high removal costs and liability of larger trees. They are also friendlier for planting around above ground utility lines.

Aspen

Ironwood (Ostrya virginiana) – Tough native tree. Slow growing and long-lived. This tree thrives in part sun, but will do ok with a little more sun too. Turns yellow in the fall and has interesting “fruit” in fall and winter.
Aspen - Aspen is a popular native tree that is medium height and medium to fast growth rate. It grows straight and upright and the leaves “quake” in the breeze. Nice yellow fall color and white to gray smooth bark.

Decorative "Cones" and Catkins of the Alder

Black alder – This is not a native tree, but nice for our urban yards. It has a medium to fast growth rate and beautiful lush leaf. One highlight is in the winter when the little “cones” (actually strobile) and catkins hang like ornaments on a tree. Insignificant fall color.

Flowering Trees:  When we design yards, we like to add at least one tree for flowering interest (usually in the spring) and one for fall interest. Here are some of our favorite flowering trees.

Crabapples in Bloom

“Prairie Fire” Crab Apple – This is a time tested crab apple that has stunning dark pink flowers in the spring. In our opinion, crab apples are to the Midwest what cherries are to Japan. Experiencing a city street lined with crab apples in bloom is one of the most dramatic natural events in our urban realm. Always make sure to purchase only crab apples that are disease resistant.
Buckeye – Not generally purchased for its flowers, buckeyes have unbelievable flowers. This underused tree has an interesting leaf, flawless form that requires little pruning and a relatively slow growth rate that insures it will be a great tree in your landscape for a long time. Ok fall color.
Catalpa – A tree that has its downsides, when the flowers are blooming and filling the neighborhood with its sweet scent you can easily forgive them. This is an upright tree that eventually gets quite large and is prone to trunk rot. Catalpa can be kind of “messy”, but it’s really noteworthy, huge tropical-looking leaves and interesting dangling seed pods, along with its amazing flowers make up for some of its short comings.

Trees for Shade:  Our urban yards often have areas of significant shade. Here are some trees that we use for those areas.

'Autumn Brilliance' Serviceberry Flowers

Serviceberry - We use more serviceberry than any other tree. Although we often use the cultivar “Autumn Brilliance” many of the species are equally usable. Serviceberries (also called Juneberry and other) have a nice white flower in spring, interesting silvery smooth bark and edible fruit in the fall if you can get to them before the birds. It also has great fall color with a little sun. There is a nice large specimen along the parking lot at the Peace Garden in Minneapolis.

'Northern Strain' Redbud in Spring

“Northern Strain” Redbud – While most redbuds are only hardy to Zone 5 (we are Zone 4), this one has been successful for over thirty years. Redbud has stunning pink flowers that burst from the twigs before the plant leafs out. This is not a plant that we feel is “guaranteed” to survive for 30 or 40 years, but we still think it is worth planting for its spring flowers as well as the nice large, lush leaves for shady spots.
Blue beech (Carpinus caroliniana) – Blue beech is a native woodland understory tree that has interesting “muscle-y” silver bark. With a little sun, it gets strong yellow to purple fall color and, similar to ironwood, dangling seeds in the fall.

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by Ann DavenportQuaking 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 woodUnfortunately, 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

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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.

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Shannon and I were driving to a client site yesterday via 42nd St. in south Minneapolis. WOW! The entire street is lined with crab apples – and, in this high season, is literally draped in pink and white flowers. I think our crab apples must rival the Japanese cherries in this glorious time. The flowering doesn’t last long so if you have time head down 42nd St. between Hiawatha and the river, or the east side of Lake Nokomis, or the MN Landscape Arboretum or the Japanese Garden at Normandale College.

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Sometimes it takes a grove of a particular tree to express its positive characteristics. If you are driving down Colfax somewhere around the 48 hundred block you will suddenly notice a grouping of trees that give the block an ethereal feel. These are tamaracks – a tree that can easily look out of place by its lonesome, but in natural clusters takes on a totally different hue.Many Minnesotans share a fondness for tamarack trees built up from trips to the cabin where the trees bright green early season leaves and especially the trees brilliant gold fall color make it remarkable. But few take advantage of these characteristics in their urban homes. Take a drive by the trees on Colfax and see what you’re missing.

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