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Archive for April, 2012

Bark beetle bore hole and larval galleries

Our new woodland garden replaces our front lawn!

Our new woodland garden replaces our front lawn! We planted a little pink dogwood, hosta, and several azaleas. Now it just needs some mulch.

Today is National Arbor Day!

It’s always the last Friday in April although some states recognize a different State Arbor Day that corresponds better with planting times in their state. Since Arbor Day was founded in 1872, it has been customary to plant a tree in observance of the holiday and on that first Arbor Day, it is estimated that about one million trees were planted.

As you celebrate Arbor Day this year, keep in mind that as important as it is to plant new trees, it is equally important to care for and protect the trees that are already growing in your landscape.

Damage to mature trees due to insects and diseases (many introduced from other countries) can be devastating to your landscape as well as the surrounding areas and adjoining forests. Diseases such as the Chestnut blight and Dutch elm disease and exotic insects like the emerald ash borer and the Asian long-horned beetle have killed tens of millions of trees across the U.S.

Chestnut blight canker on the stems of a young American Chestnut. Photo by Eric Jones

Chestnut blight canker on the stem of a young American Chestnut.
Photo by Eric Jones

The chestnut blight, caused by a fungus (Cryphonectria parasitica), was introduced to North America from Asia in the early 1900’s either on infected lumber or through diseased trees. Within 40 years of its introduction, virtually all the chestnut trees in North America were wiped out. Although mature American chestnut trees have disappeared from our forests, small trees often grow from stump sprouts since the blight doesn’t kill the roots. Unfortunately, these small trees rarely grow to reproductive age before they are attacked and killed by the fungus. Such a sad ending for these once majestic trees which often reached 200 feet tall and 14 feet across! There is no cure for this disease but much work has been done to genetically engineer a disease resistant American chestnut using genetic material from a few stump sprouts that managed to produce seeds and a bit of DNA (as little as 3%) from Asian species that show resistance to the blight. The American Chestnut Foundation is at the forefront of this research with a mission …

…to restore the American chestnut tree to our eastern woodlands to benefit our environment, our wildlife, and our society. The American Chestnut Foundation is restoring a species – and in the process, creating a template for restoration of other tree and plant species.”

How’s that for a great Arbor Day message!

Woolly adelgids on the branch of a young hemlock.

Woolly adelgids on the branch of a young hemlock. Photo by Eric Jones

Another pest that is doing its best to wipe out whole a species of trees is the hemlock woolly adelgid (Adelges tsugae). This past Sunday on a wonderful but rainy walk in the George Washington National Forest, Eric and I saw evidence of this destructive pest on a young hemlock. The hemlock woolly adelgid was also an accidental introduction from Asia and is devastating populations of eastern hemlock (Tsuga canadensis) and Carolina hemlock (Tsuga caroliniana) throughout eastern North America. The insect damages the trees by feeding at the base of the needles causing them to desiccate and eventually drop off. Heavy infestations have been known to kill trees in as little as four years but healthy trees can sometimes survive an attack for a longer period of time. Luckily, there are products that the homeowner can use to help control hemlock woolly adelgids but sadly in our hemlock forests, these pests are causing the destruction of large numbers of these beautiful trees. Read more about the woolly adelgid.

As they have with the American chestnut, researchers have developed an adelgid-resistant hybrid by crossing the Carolina hemlock with an Asian hemlock which is resistant. While this is great progress – it does nothing to save the trees that are already infected!

Seen these hanging around?

Seen these hanging around? These purple structures are Emerald Ash Borer traps used to evaluate populations of the pest.

Another group of insects that causes widespread damage to established trees is the wood-boring insects including the emerald ash borer, the Asian long-horned beetle (both introduced from Asia), and a wide variety of the bark beetles.

The emerald ash borer, first reported in Michigan in 2002, has already killed millions of ash trees and is a potential threat to all the ash trees in North America.

The Asian long-horned beetle is one of the most destructive of the wood borers because it is not selective and attacks a wide variety of hardwood trees.

Bark beetles, like the spruce beetle, the mountain pine beetle, and the southern pine beetle, have killed millions of conifers in North American forests especially during severe outbreaks.

Bark beetles attacked this weakened pine and contributed to its death.

Bark beetles attacked this weakened pine and contributed to its death.

I remember when we were in Alaska several years ago seeing where the spruce beetle had killed entire forests of Sitka Spruce. Although bark beetles generally attack trees that are weak, dying, or already dead, the species listed above are particularly destructive because they will attack live, seemingly healthy trees.

For the homeowner, there are products that can be used to help control some of these pests. Horticultural oils can help control the woolly adelgid if they are sprayed at the correct times.

Some systemic insecticides may help control adelgids, emerald ash borers, Asian long-horned beetles, and pine borers. Bayer Advanced 12 Month Tree & Shrub Protect & Feed II and Bonide Annual Tree & Shrub Insect Control are products that can be mixed and poured at the base of the tree according to the label directions. These products are not available in all states. Always read and follow the label directions when using any pesticides. Read more about borers.

On this Arbor Day, The Nature Conservancy reminds us of some important tips to help protect our trees.

  • Keep your trees healthy and vigorous! Many destructive insect pests and diseases are attracted to trees that are stressed due to poor nutrition, drought conditions, and mechanical injury such as lawn mower or weed whacker nicks in the trunk.
  • When purchasing trees, purchase certified, pest-free nursery stock.
  • To avoid inadvertently spreading invasive pests or diseases, NEVER transport firewood when you travel, always obtain it locally!

So make a pledge this Arbor Day to pay attention to your existing trees and strive to keep them strong and healthy!

… and plant a tree!

Until next time – Happy Gardening!

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Vole runways wind through the dead grass after the snow melts.

Wee, sleekit, cow’rin, tim’rous beastie
O, what a panic’s in thy breastie!”

Voles can do a lot of damage to trees, shrubs, and perennials in the landscape.

Voles can do a lot of damage to trees, shrubs, and perennials in the landscape.

The beginning of the poem, “To a Mouse” by Robert Burns, came to mind when “Bo”, our field manager, came to me this morning exclaiming, “I’ve never in my life seen so many voles before!”

“Bo”, a.k.a. Tim, was bush hogging a field that hadn’t been cut for a long time and he had been watching hordes of voles (Microtus spp.) running in all directions to get out of the way of the tractor. Good thing they were able to hear (and feel) it coming from a distance so they all managed to flee to safety!

He called me over to the field so I could see the extensive runway systems and holes that the voles had created throughout the overgrown field. It was pretty impressive what these little critters had managed to do to this abandoned field.

Meadow voles can create major highways under the cover of snow!

Meadow voles can create major highways under the cover of snow!

In the spring of 2010, we had a post on our Discussion Board asking about “strange marks/trails in my yard … These trails are 1-2 inches wide with smooth turns. The grass is ripped out of the ground and deposited to the edges of the tracks. These appeared in the late winter after snow melt.”

He included some photos and it was pretty clear that they were vole runways. Voles can be very active under the snow because when there is snow cover, they don’t have to worry about predators as much and they can have a real party under there!

The same thing happens when there is a heavy cover of tall grass, although our resident barn owls have no trouble catching as many voles as their fluffy little owlets can eat – and that’s a lot!

Cozy entrance to a meadow vole runway.

Cozy entrance to a meadow vole runway.

In a field, voles usually aren’t much of a problem but in the landscape or orchard, they can be devastating to your perennials, shrubs, and trees. Plant injury from vole feeding can be severe enough to cause significant decline and/or death of many ornamentals and edibles as well. They absolutely LOVE Astilbe and hosta and we have lost many of our prize hosta to their voracious appetites. Although we have not experienced damage to our fruit trees so far, the tender bark of apple trees and other fruit trees is another of their favorite meals. Voles can girdle trees by chewing the bark or devour whole root systems causing the death of the trees.

In many cases, the damage from voles may go undiscovered until the decline or death of a particular plant is noticed. Trees and shrubs which have had their roots chewed will eventually begin to wilt and may even fall over. If the damage is severe, they can often be pulled right out of the ground with very little effort. In vegetable and perennial gardens, entire plants may disappear completely or be partially pulled underground.

So what can you do if you have voles in your garden?
Moles and voles can be difficult to get rid of and some say the only way is to trap them. Many of our gardening friends have had success with certain repellents such as:

    • Bonide MoleMax (Granules and Ready to Spray)
    • Bonide Repels All
    • Mole Scram
    • Liquid Fence Mole Repellent

These repellents are biodegradable and safe to use around children and pets when applied according to label directions.

MicrotusAnother effective way to protect plants and bulbs is to create a barrier between the vole and its lunch! Voles don’t like to tunnel through coarse materials, so when you plant, surround your plants with a coarse aggregate that has jagged edges. Espoma Soil Perfector is perfect for this; it’s safe, nontoxic, lightweight, and easy to use. Soil Perfector also promotes rooting and since it doesn’t breakdown, it creates a permanent barrier.

Tree guards are another effective way to protect your young trees from vole damage. The green tubes you see neat rows of in many fields are there to protect saplings from vole damage. When set-up correctly, they go several inches into the ground and prevent voles from reaching the tender trunks.

Here are a few more ideas to protect your trees and shrubs from vole damage.

If you have these critters in your garden – I’m so sorry! We have them now, too. We never had a problem with them when our outside cat was alive. He kept them out of the gardens for many years. I guess it’s time to replace him – I’m tired of my hosta disappearing!

Until next time, Happy Gardening!

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The lacecap hydrangeas are beautiful when they bloom.

The new growth on the boxwood was severely damaged

The new growth on the boxwood was severely damaged

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Everyone has been talking about the early spring we’re having and how far along all the plants are. All this warm weather has many people forgetting the fact that it really IS still early spring and that frost and freezes are still VERY LIKELY. In fact, many areas of the country have had a rude awakening in the past few weeks as nighttime temperatures have dipped below freezing for the first time in a while. I talked to my mom and dad in Vermont last night and they recently had lows in the teens and even had snow this week.

This is just Mother Nature reminding us what time of year it really is!

The flowers and new foliage of the deciduous magnolia were damaged by frost.

The flowers and new foliage of the deciduous magnolia were damaged.

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Walking through the gardens, I have seen quite a bit of damage from the recent freezing temperatures. Some of the dogwood blooms have been burned and the deciduous magnolia flowers and its new foliage took quite a hit. Even the new growth on the boxwood and Buddleia, which emerged very early this year, has been nipped. Most of this will have to be pruned off. But the worst damage I noticed was on the new foliage of the lacecap and mophead hydrangeas.

We have three beautiful lacecaps at our house that my sister gave us when she realized that they were not bloom hardy in Vermont. They have established well for us and have bloomed beautifully over the years (see blooms at the top). Every once in a while the flower buds get zapped in the winter and they don’t bloom but in the last few years, as the shrubs have matured, the bloom has been spectacular.

Frost damage on my lacecap hydrangea

Frost damage on my lacecap hydrangea

Right now these poor shrubs look rather pitiful. They broke dormancy very early with the warm March temperatures and the foliage was fairly advanced when the first cold snap occurred 2 weeks ago. Since then we have had several more nights where the nighttime temperatures dropped below freezing. At this point, the foliage is quite damaged and I feel this does not bode well for our chances of having flowers this year. Time will tell!

Frosts are funny things. They can sneak up on you sometimes because the temperature doesn’t necessarily have to drop below freezing for a frost to occur. If the night is clear and the winds are calm, frost can occur even at 38oF or 40oF. These are called white frosts.

Tender new growth on this butterfy bush was burned back by the frost.

Tender new growth on this butterfly bush was burned back by the frost.

White frosts generally occur when temperatures are at or above 32oF and are usually less damaging to plants than a black frost. They typically cause mainly surface damage – what we call “burning” of the foliage.

Black frosts occur when temperatures fall below 32oF – usually when it drops to around 28oF or lower.

Black frost is always a killing frost because it damages plant tissue and causes a blackened appearance to the foliage. Perennials and woody plants can get pretty severely knocked back but generally they will recover and put out new foliage.

New growth has begun to leaf out on my hydrangeas. I hope it doesn't get zapped tonight!

New growth has begun to leaf out on my hydrangeas. I hope it doesn't get zapped tonight!

I think the damage in our area was mostly due to white frost. The more susceptible herbaceous perennials in the Viette gardens were largely spared from injury because Mark and Andre had many sections of the gardens draped in cover cloth for protection; especially the tender new hosta foliage which is very prone to frost and freeze damage.

If your perennials did suffer frost damage, many plants, such as hosta, ferns, Astilbe, Kirengeshoma, Cimicifuga, and Japanese anemones, can be cut back completely and they will regrow with fresh new foliage. If the damage isn’t widespread on the plant, just trim off the damaged parts.

Just remember – the cold weather is not over! In fact, it was snowing here just a few minutes ago – really! The very warm March days fooled many of us into thinking that we were done with frosts and freezes – not so! Watch for more spring frosts – April can be very unpredictable.

Be patient and don’t rush out to plant your tomatoes and annuals just yet. Pay attention to the average date of last spring frost for your area and plant according to that date – just to be safe!

Until next time – Happy Gardening!

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Beautiful dogwood blooms

Our woods are full of native dogwoods (Cornus florida). In the spring, their white “flowers” provide a colorful and very beautiful effect in the awakening forest. We’re just beginning to see that this week. In a few days, the woods will come alive with soft clouds of white as the dogwood bracts expand to their full size.

Airy layers of dogwood blooms brighten the spring woodland.

Airy layers of dogwood blooms brighten the woodland in the spring.

Dogwoods of various sizes and stages of maturity are the dominant understory trees in our woods. At the time they come into bloom, the woodland is still colored in the browns and grays of the bare oaks and hickories and the tan shades of the leaf covered forest floor. This dark backdrop really allows the white dogwood blooms to stand out.

One of my strongest memories of these beautiful trees comes from when I was doing research in the Sandhills region of North Carolina. The flowering dogwood is the dominant understory tree in the longleaf pine forest where we were studying the southeastern fox squirrel. In the spring, the dogwoods would burst into bloom before anything else and the beautiful layers of white blooms stood out brilliantly against the dark trunks of the tall pines and the carpet of pine needles on the ground – absolutely stunning! I really wish I had a picture.

Monolayering leaves all branches exposed to the sunlight.

Monolayering leaves all branches exposed to the available sunlight.

There is a really interesting story about the growth form of these trees and how it varies depending on the amount of sun they receive. Dogwoods that grow under the shady conditions of mixed hardwood or pine forests develop a unique growth pattern which truly adds to the beauty of the tree and its overall attractiveness in the woodland setting.

In the shade, these trees (as well as many other understory trees) tend to have a sparser crown with branches that spread out horizontally resulting in a rather flat-topped, layered appearance. When these dogwoods come into bloom, this horizontal branching pattern is especially obvious and it creates a really beautiful effect – like low clouds floating through the forest.

This dogwood growing in the open is heavily branched and has developed a fairly symmetrical crown.

This dogwood growing in the open is heavily branched and has developed a fairly symmetrical crown.

The branches of woodland dogwoods are arranged in alternating layers so that one branch never shades the branch growing below it. This allows all leaves to have maximum exposure to the available sunlight. This form develops as the tree grows because branches that are heavily shaded by another branch eventually die off due to lack of sun. The branching pattern, called monolayering, allows the tree to maximize photosynthesis under the lower light conditions that occur in the interior of mature forests.

In contrast, dogwoods that grow in more open habitats where competition for sunlight is not a factor usually have a much denser crown with overlapping layers of branches (multilayered).

Looking up through the multilayered crown of a dogwood growing in the sun

Looking up through the multilayered crown of a dogwood growing in the sun

In the forest, the majority of the sunlight reaching a tree comes from above, while in an open field, light reaches the tree from the sides as well. This allows more branches to harvest sunlight and the airy layers seen when the trees are growing in shade are much less pronounced or even lost all together.

We have a beautiful dogwood that is growing out in the open on the way up to our orchard. This tree, which is exposed to much more sunlight, shows the very striking difference between the two growth forms.

A beautiful dogwood growing in the sun in one of the Viette gardens.

A beautiful dogwood growing in the sun in one of the Viette gardens.

Trees grown in the landscape in full sun or high shade often have more lower branches than forest trees of the same species. When you walk through the woods and see an old tree with massive lower branches you know that this tree once held vigil over a field or clearing. If you find a tree that has large branches on one side only, then it is probably growing or once grew at the edge of a field with the lower branches pointing towards the field.

Here’s one more bit of interesting tree growth trivia:

When trees are planted for timber harvest, the seedlings are planted close together to discourage the development of lower branches which would form knots in the wood and reduce the value of the timber.

Such cool stuff! Next time you are walking in the woods or around your yard take a look to see how the dogwoods grow!

Until next time – Happy Gardening!

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