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MIDSUMMER LEAF DROP AND FRUITLESS PLUMS

GARDEN TIPS – Written by Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Published August 14, 2016

Tree anomalies have a way of occurring from time to time over the years. They are signs of potential problems that justifiably alarm tree owners. Recently, some local tree owners became concerned when a considerable number leaves on their trees started to turn yellow and drop on the ground.

Midsummer leaf drop occurs before the arrival of fall and is usually related to heat stress. As you can imagine, excessively hot days can stress trees, especially species not well suited to hot climates. The root systems of these trees are not able to keep up with the water demands put on the trees by high temperatures. Some types of trees respond to heat stress by getting rid of some leaves, thereby limiting the loss of water through their leaves. Other types of trees develop leaf scorch (brown, dry edges on the leaves) when they cannot keep up with the water demand caused by hot weather.

In our area, sudden yellowing and dropping of numerous leaves due to heat stress has been noticed on birch, cherry, Liriodendron (tulip), linden, sycamore, and willow trees. This year’s midsummer leaf drop was probably more pronounced because of the abrupt change from moderate weather to high temperatures.

Drought stress can also lead to tree leaf drop, especially when paired with heat stress. During hot summer weather, it is important to provide your trees with the water they need via deep watering. Large shade trees seldom receive adequate water when getting moisture only through lawn irrigation. It is important in hot weather to provide trees with a deep watering at least once a week.

How much water do trees need? They need a lot of water because they lose a lot through the pores, called stomata, in their leaves. Adequate irrigation is extremely important. To determine how much water your shade tree needs, go to the WSU Irrigation website and use their Tree Water Management Calculator at http://irrigation.wsu.edu/Content/Calculators/Residential/

A Supposedly “Fruitless” Plum Tree with Fruit: It can be annoying for owners of a flowering plum tree when their supposedly fruitless plum occasionally or frequently produces a prodigious crop of plums. When this happens, I get asked the same two questions. Why did this happen and are the fruit edible?

The production of fruit on ornamental plums is not a reliable occurrence, but it can happen if their bloom overlaps that of other types of plums. Typically, purple-leaved flowering plums bloom in early spring before other plums are flowering, limiting the possibility of cross-pollination and fruit development. Before buying a flowering plum tree, check with your nursery to make sure the cultivar you are selecting is rarely fruitful in our area.

As to edibility, the fruit can be eaten, but are generally of poor quality for eating. The trees were bred for their beautiful flowers, not their fruit. If you are a thrifty gardener, you might try making jam with the fruit and see if it is tasty enough to be worth your time and trouble. Do not use the fruit if the tree has been treated with pesticides not labeled for use on edible fruit trees.

Garden Note: Whenever applying pesticide to a tree with edible fruit, check the label for the “days to harvest” or the number of days after application that you must wait before harvesting the fruit. Also, make sure the type of fruit receiving the application is listed on the label.

THERE ARE NO PERFECT TREES

GARDEN TIPS – Written by Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Published July 10, 2016

I am often asked what the best trees are for planting in our region. However, this query typically includes certain criteria that make my answer more challenging. Homeowners want a tree that does not get too big, does not produce messy fruit or seeds, does not have insect or disease problems, or does not have invasive roots or surface roots. Their ideal tree also has pretty flowers in the spring and attractive fall color, grows quickly, and tolerates our local soils and climate well.

If you are waiting for a list of the trees that meet these criteria, you will have to keep waiting. There are no perfect trees. Every tree has one or more characteristic that is objectionable in some way.

Leaf Litter: If you own a mature sycamore or silver maple, you know that large trees with large leaves produce large volumes of leaves, creating a raking and disposal nightmare in the autumn. Mature large trees can be magnificent. However, when studying what type of shade tree to plant you, may want to consider trees, such as little leaf linden or river birch, with smaller leaves that produce a smaller volume of fall foliage.

Seed and Fruit Litter: Generally, trees are going to produce litter in the form of seeds or fruit. I frequently hear complaints about the massive amounts of seeds produced by some maples and Siberian elm, as well as the seed balls of sycamore and sweet gum trees.

The fruit of ornamental plums, crab apples, and cherries can provide food wildlife, but this fruit can be very messy when ripe and mushy, especially if the tree located close to pavement. Some fruit trees, even ornamental fruit trees, are subject to attack by the cherry fruit fly or the codling moth. County law requires that these pests be controlled even in ornamental fruit trees. This requires regular pesticide applications.

Gingko fruit smells like dog manure and mulberries will turn white tennis shoes permanently purple. Catalpa, Kentucky coffee tree, and honeylocust can create an abundance of bothersome litter with their seed pods.

When selecting trees, look for seedless and fruitless cultivars. For example, the Autumn Blaze maple is a hybrid cross between red and silver maple. It is seedless or pretty much seedless. If you find those spiny seed balls of sweetgum trees a problem, look for ‘Cherokee’ or ‘Rotundiloba’, both virtually seedless sweetgum cultivars. If you like gingko trees like I do, be sure to purchase a male tree, as only female trees produce the stinky fruit. If you like mulberry trees but want to skip the fruit, find Morus alba ‘Fruitless’ that does not produce berries.

Bark and Twig Litter: Some trees, like sycamore, have bark that sloughs off and in some years they can create considerable annoying bark litter. However, this does create an attractive mosaic bark pattern. Siberian elms and birches have a tendency to drop twigs all the time that must be cleaned up before mowing. Since river birch is one of my favorite trees, I am willing to tolerate this annoying tendency.

Nut litter: Mature nut trees, such as walnut, horsechestnut, Chinese chestnut, and oak all produce fairly large hard or spiny fruit. Before planting nut trees, be sure to consider the fruit that will eventually be produced.

There are no perfect trees, but some research before you buy and plant a tree will help you avoid trees that create a mess and more work for you.

BROWN AND DEAD EVERGREENS PART 2

GARDEN TIPS – Written by Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Published June 19, 2016

Last week I covered the top two factors contributing to the browning and dieback of many area needled evergreens. While it is no surprise that heat and drought stress could cause problems, some of you might wonder why we are just becoming aware of the severity of the situation.

It is easy to tell when a tomato or squash plant is suffering from drought or heat stress. They wilt. This is not the case with trees, especially conifers. Browning needles and excessive needle-drop are telltale signs of stress, but a conifer may not exhibit browning until some time after the damage from stress has occurred. Why is that? Conifer needles have a very waxy coating that slows their drying out, delaying browning, diagnosis, and preemptive action.

I will also point to the cumulative stress from three successive years of extraordinarily hot summers and minimal winter precipitation. Many of these conifers have been declining over that time, but the additional stress year after year has pushed them past the tipping point.

So what about trees that are turning brown despite their owners watering correctly, keeping the top 18 inches of soil moist and mulching to keep the roots cooler? Restricted or girdling roots, the result of improper planting, are often involved in helping push trees over the edge.

Container grown plants are frequently pot-bound with circling roots or very dense, matted root masses. If these roots are not properly cut and loosened at planting time, the roots will not move out into the surrounding soil where they have access to moisture and nutrients. Eventually the roots will girdle or Achoke@ the plant, preventing the uptake of water, and killing the tree. The signs will be that same as signs of drought and heat stress.

A similar problem occurs with balled and burlapped trees that are grown in the field, dug, and their root ball wrapped in treated burlap. In our dry climate, the burlap does not decay quickly enough to allow for good root growth out of the original root ball. University horticulturists, landscape professionals, and The American National Standards Institute (ANSI) all indicate that the burlap should be removed before planting.

Also, the soil in the root ball is commonly very different from the native soil where the tree is being planted. This can lead to difficulty in keeping the soil in the root ball and surrounding soil moist, but not excessively wet.

Soil compaction restricts root growth and can contribute to a tree=s demise. This is because compacted soil has less air available for the roots and roots need air to function. In addition, soil compaction physically impedes root growth. In older landscapes, soil becomes compacted over time from traffic and even sprinkler irrigation. In newer landscapes, the soil may be highly compacted due to the use of heavy construction equipment during building.

Where trees are growing in lawns, periodic aeration can help relieve some of the compaction. However, if the compaction is severe, a certified arborist may recommend more extreme measures. When planting a new landscape, the soil should be properly prepared with tilling before planting.

This week and last week I have mostly focused on the browning and dieback of conifers in our area, but we are also seeing dieback on some local deciduous trees and shrubs. Depending on the plant=s situation, this decline may be attributed to the same factors causing the browning on conifers. I sure hope this summer is cooler. How about you?

WHY ARE THE EVERGREENS DYING?

GARDEN TIPS – Written by Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Published June 12, 2016

I noted earlier this year that our last three summers have been abnormally hot with record breaking heat. Even before I started getting calls about dying arborvitae, pines, cedars, and other conifers, I predicted that the stress caused by extreme heat and inadequate watering practices was going to lead to the decline of many area trees. We can not do anything about the weather, but we can try to avoid the same problem in the future by reviewing the contributing factors.

Before we do that, let’s talk about the needles on conifers. While we call trees with needles “evergreens,” they do shed or drop their oldest needles ever year. Evidence of this is the bed of needles underneath pine trees. This is not a problem for healthy trees that are producing a new set of needles each year. These new needles persist on a tree for a year or more. Depending on the species, pines will hold their needles for two or more years and spruces for five years or more. However, if a conifer is stressed or its health is compromised by insects or disease, the production of needles will be reduced or stop altogether. This stress can also lead to the browning and shedding of more than just the oldest needles. As a result, a tree will have fewer and fewer green needles, a sign of its decline.

Drought: We are in a region with very limited precipitation, making adequate irrigation essential to growing healthy trees. Many homeowners assume that their trees are getting enough water, but they do not check the soil moisture in the tree’s root zone to make sure.

The water absorbing roots of most landscape trees are within the top 12 to 18 inches of soil. It is this zone that should be kept moist with deep watering. Watering trees just with the lawn for 15 to 20 minutes once or twice a day may not be enough to moisten the soil to the needed depth. It of course depends on how much water is being applied, weather conditions, and the type of soil. The only way you will know if the soil is moist enough is to use a trowel to dig down and check.

It is also important to moisten the soil where the water absorbing roots are located. They are not close to the trunk or under the canopy of mature trees. They are located at and beyond the canopy or outermost spread of the branches called the “drip-line.” It is to this area that water should be applied.

Heat Stress: We can not offer much relief from the heat to established trees, but when planting new trees we should consider planting trees that are well adapted to hot summer weather. If you plant a species that is not well suited to our climate, select the site carefully to provide it with protection from sun, heat, and wind. On younger and smaller trees, mulch the root zone with three or four inches of wood chips or bark to keep the roots cooler and to maintain soil moisture.

Oh my, I have come to the end and I have not had the chance to talk about soil compaction and other factors contributing to local conifers turning brown. More next week…

SUMMER HEAT TOUGH ON PLANTS NOT WELL ADAPTED TO OUR HOT SUMMERS

GARDEN TIPS – written by Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Written Septembe 13, 2015

SUMMER HEAT TOUGH ON PLANTS NOT WELL ADAPTED TO OUR HOT SUMMERS
Two years of record heat is just too much. I am tired of seeing samples of crispy brown plants and being asked the cause of the problem. Quite simply, it has been hot and difficult for plants to survive, especially plants that are not well adapted to our climate.

Several weeks ago I took a look at some local Norway and Colorado spruces that were turning brown and dying. While not always the best clue to the origins of a plant, these spruces’ common names do give us a hint that they may not be well suited well to the hot, dry summer weather of the mid-Columbia. Norway spruce is native to northern and central Europe and prefers a cool, moist, humid climate. Colorado spruce, native to the central and southern Rocky Mountains of the US, is also best adapted to a cool, humid climate.

In their publication on “Spruce Problems” the University of Illinois points out that spruces as a group “prefer locations with acidic, well drained soils” and that “spruces are not well adapted to hot dry locations and often suffer when planted in the warmer regions of the US.” In this publication they also discuss heat injury of spruces, indicating that high temperatures can cause heat damage, especially when the high temperatures are preceded by cool weather. Heat damage on spruces is expressed as browning and dropping of new needles, leaving dead branch tips. After two or three years of this, a spruce is pretty much dead.

Just because spruces are not well suited to our climate does not mean that you can not find healthy spruces growing locally. However, our climate does stress them and make them more vulnerable to attack by a number of pests, like spruce mite, bud scale, and needle miner. I did find spruce bud scale on one of the browning Norway spruces, but the infestation was not severe enough to kill the tree. At least we can be thankful that our dry climate keeps fungal diseases that infect spruce from being a problem here.

Flowering dogwood is another tree that suffers when faced with hot, dry, windy summer weather. In its native habitat, it is an under-story tree that grows in the filtered shade of other forest trees. It grows best in a moist, well-drained, slightly acidic soil that is high in organic matter.

Dogwoods become stressed when planted in full sun and subjected to high temperatures, reflected heat and light from pavement and structures, wind, compacted soil, and poor watering practices. This stress shows up as curled leaves and crispy brown leaf edges. Nevertheless, many of these trees still put on a beautiful display of flowers each spring. To help dogwoods better cope with mid-Columbia conditions, plant them where they will have filtered shade and will not be subjected to a southern-western exposure or drying winds.

Dogwoods and spruce have very shallow root systems, making them more subject to drought and heat stress. It is advisable to keep the roots cooler and moist by mulching the roots with wood chip or shredded bark mulch. Apply a 3 to 4 inch layer of mulch all the way out to the tree’s dripline and beyond. Keep the soil moderately moist, but avoid excessive soil moisture. Be sure to water the spruces during the winter if the weather stays dry and mild.

I hope next summer is a little cooler, don’t you?

ARE ROOTS STRANGLING YOUR TREE?

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA
published- AUGUST 8, 2014

ARE ROOTS STRANGLING YOUR TREE?

When a homeowner comes to me with a sample of a sick tree, I look for signs and symptoms. Signs are the actual culprit causing the problem, such as aphids or a whitish coating on leaves from powdery mildew fungus. Signs make diagnosis easier and more definitive.

Symptoms tell you something is wrong, but not what is wrong. Symptoms include wilting, distorted growth, dieback, and more. I have to rely on symptoms to determine the most likely causes of a problem.

I also gather information about how the tree was planted, its care, and descriptive details of the problem. Often I cannot provide just one definite cause because there may be a variety of cultural factors involved. I suggest the most likely possibilities and the owner must go home and try to determine the actual cause and then remedy the situation.

ARoot problems@ is a nebulous term I often render as a diagnosis. Many tree problems are related to the roots, the soil and watering practices. A common Aroot problem@ is a stem girdling root (SGR). SGRs have become a problem for tree owners ever since the nursery industry began growing trees in containers instead of in the ground.

The SGRs start when the roots reach the sides of pots or containers and then begin circling the container. This creates roots which encircle the main stem, either partially or sometimes entirely. If not corrected at planting time, these roots will continue to grow in the same pattern. As trees get bigger, their roots grow in length and girth.

Eventually, a SGR will start choking off the flow of water and nutrients from the roots. Depending on how quickly the tree grows and how severe the strangling, SGRs can lead to a tree=s demise within several years of planting or… ten years or more in the future.

As a result of SGRs, a tree will exhibit symptoms that indicate something is wrong. These can include crispy brown leaf edges (leaf scorch), stunted growth, yellowing leaves, leaf drop and gradual dieback of branches and entire limbs. However, these same symptoms can be caused by other problems, such as chronic drought stress, physical damage to the trunk or roots, and compacted soil.

To determine if the problem is being caused by SGRs, owners must do some of their own detective work. While some SGRs are visible at the base of a tree’s trunk, others are not. Detection requires looking for clues and possibly doing some excavation.

Tree trunks usually flare out at the base, some species more than others. A clue that one or more SGRs is involved is a lack of flare or even an indentation at the base of the trunk. If this is noted but no SGR is visible, the soil in that area should be carefully excavated using a trowel and not-too-strong jet of water. Many, but not all, SGRs will be found in the top several inches of soil.

If a sizable SGR is found on a large tree, I recommend hiring a certified arborist to assess the situation. They will excavate the SGR and use a sharp chisel or saw to cut the root where it attaches to the trunk. If the SGR is deeply embedded in trunk tissue, they will leave it in place after severing. If removal will not damage the plant, they may remove it.

Are your trees being strangled by SGRs?

Published: 8/8/2014 11:37 AM

YOUNG TREES SUDDEN DECLINE

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA

Wow! After such a cool spring this hot weather has come as a shock to us and our plants. A number of local residents have been dismayed to find their landscape trees suddenly dying. It’s likely that many of these trees showed signs of decline in the past, but the stress from the sudden onset of summer has been a tipping point.

There are two main categories of trees biting the dust, newly planted trees that have been in the ground for less than three years and trees that have been in place for longer.

Today, let’s talk about the young or newly planted trees. In the past, I’ve talked at length about the correct way to plant trees. Rather than repeat myself, you can obtain a free copy of a WSU Extension publication ‘FS047E Planting Trees and Shrubs in the Landscape ‘ at pubs.wsu.edu.

Let’s discuss how to investigate why young trees are dying. First, check the root system to find out if it’s grown out of the original root ball. According to tree expert, Dr. Gary Watson of the Morton Arboretum, ‘under favorable conditions, roots can be expected to grow approximately 18 inches per year. ‘ So if you planted a tree correctly last spring, this year you should be able to find roots growing at least a foot or more away from the original root ball, even more if it’s been in the ground longer. Carefully dig down to find out if the roots have indeed grown out from the root ball. Use a trowel and a hose to carefully excavate for roots, starting at the perimeter of the original root ball.

How are the young trees being watered? Many conscientious gardeners wanting to conserve water have shifted their trees and shrubs, particularly those in landscape beds, to drip irrigation. When a new tree or shrub is planted, the drip is often positioned at the base of the plant. This may seem logical, but depending on the type of soil and the emitter used, the water may be simply pooling at the base of the tree and not moistening the entire root ball and the area beyond. This results in a poorly developed root system and a drought stressed plant.

Again use a trowel to check the moisture in the root ball and in the soil just beyond where the roots are growing. It’s crucial to have roots growing into the surrounding soil as the top of the tree grows bigger. Those roots are responsible for absorbing water and nutrients to support tree growth. If that doesn’t happen, the tree can’t grow into a healthy older tree.

Don’t place drip emitters right at the base of a young plant, position them several inches or more away from the trunk. Keep in mind that as the tree roots grow outwards, the moisture needs to be applied in the area of the outward edge of the roots and just beyond. That’s where the fine roots that take up the water and nutrients are located, not at the trunk. You should adjust your system to be moistening the soil to a depth of 18 to 24 inches in the root zone, not at the base of the trunk. This may require using more emitters, sprinkler-type emitters, or a soaker hose.

For young trees located in lawn areas, don’t rely on lawn sprinklers to provide adequate moisture. It’s likely you will need to apply additional water to newly planted trees using a soaker hose or individual sprinkler, especially during the first several years after planting.

In a week or two we’ll talk about why some older area trees may be dying.

Published: 7/20/2012 2:59 PM

ARE THERE WORMS IN MY CHERRIES?

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA

Several weeks ago a cherry tree owner brought some cherries into me to see if they were infested with cherry fruit fly. Because of an out-of-town emergency, she had missed one or more of the sprays recommended to control cherry fruit fly.

This cherry tree owner knows the importance of regular insecticide sprays to keep her cherries worm-free. However, not everyone with a cherry tree knows that regular sprays are needed to keep their cherries from becoming infested with cherry fruit fly maggots or ‘worms.’

Also, not everyone knows that county law in Benton, Franklin, Yakima, and Walla Walla counties requires that if your tree produces cherries you MUST control the cherry fruit fly or remove your tree. These laws are intended to help protect the region’s commercial cherry industry. Infested cherries trees in local neighborhoods serve as sources of infestation for commercial cherry orchards, requiring nearby growers to apply more pesticides to avoid the risk of their crop being rejected because of infested fruit.

(The same is true of fruit bearing apple, pear, crab apple, and ornamental pear trees. They’re all codling moth hosts. The law also requires the control of codling moth in these trees to protect local commercial apple and pear growers.)

What about flowering cherry trees? Do they need to be sprayed? No, most ornamental flowering cherry trees, such as the weeping cherries or the Japanese flowering cherries, don’t produce fruit and don’t require spraying. However, ornamental flowering cherries trees are usually grafted trees. The top of the tree (called the scion) is the desirable flowering variety, but the bottom part of the tree (called the rootstock) is usually a type of cherry capable of flowering and producing fruit. If the scion dies for some reason, the rootstock often grows, flowers, and produces fruit. Sometimes the rootstock grows and produces fruit even if the scion is still alive.

The bottom line is that if your tree produces fruit, it must be sprayed regularly to control cherry fruit fly. If your ‘ornamental’ cherry is bearing fruit, your best bet is to remove it and start over again with a new tree. You might want to try planting something other than a cherry!

Home gardeners have two materials available to them for cherry fruit fly control. One is malathion, an organophosphate insecticide. The other is spinosad which is considered an organic material. Either of these materials must be applied to the entire tree beginning when the fruit starts to soften a bit, typically around Mother’s Day weekend in May. Sprays are reapplied every 10 days until close to harvest, stopping when specified on the label as the ‘pre-harvest interval’ before picking.

So if you do miss a spray application or two, how can you determine if your cherries are wormy? Some backyard cherry growers find out when the worms or maggots float to the tops of canning jars after processing, but there are ways to test for them.

In lieu of actually canning the cherries, you can make the maggots separate from the fruit by crushing some cherries and then submerging the mashed mess in a jar or other container with hot (140 to 180 degrees) water. Shake the container for about a minute to kill the maggots, then strain off the pulp with 1/4 inch mesh and look for the maggots to settle out. If you’ve done a good job of protecting the fruit, then there should be no maggots at the bottom. Yummy.

Published: 7/13/2012 2:52 PM

WORST TREES TO PLANT

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA

I’m often asked about the best trees to plant in our area, but usually not about the worst trees to plant. My reasons for deeming a tree ‘the worst’ is its extremely large mature size; susceptibility to disease or insect pests that are difficult to impossible to control; invasive roots; and weak wood prone to breakage from wind and ice. So what trees do I advise against planting on the normal home lot? Here goes…

Silver Maple (Acer saccharinum): Silver maple is a common older tree in our area, planted in years past because of it’s fast growth. However, with fast growth comes weak wood and invasive roots. Silver maple is also a very large tree when it reaches maturity, much too big for today’s average home landscape. Plus, as silver maple ages, surface roots become a significant problem, lifting sidewalks and making lawn mowing difficult.

Ash (Fraxinus americana and Fraxinus pennsylvanica cultivars): Ash trees are well suited to our soils and perform quite well until they’re attacked by the ash borer which has become prevalent in our region. There is no practical control for ash borer, so the longevity of an ash tree in a home landscape is questionable.

Quaking Aspen (Populus tremuloides): Who doesn’t like the trembling leaves and the spectacular golden fall color of aspens? Many folks love this tree until it’s been growing in their landscape for a couple of years. That’s when the aspen roots start sending up suckers, lots of suckers. According to research, aspen roots start suckering when they’re about two years old and one-quarter inch in diameter, plus aspens develop extensive root systems. This explains how native aspen stands grow larger and regenerate themselves after forest fires. In home landscapes this ability becomes a nightmare.

Hybrid Poplars (Populus sp.) Hybrid poplars are created by breeding two or more poplar species together. Because poplars are some of the fastest growing trees in northern temperate zones, plant breeders have worked at creating hybrid poplars that are very fast growing for pulp, energy, and lumber production. However, the title ‘hybrid’ doesn’t equate to a good landscape shade tree. Poplars and hybrid poplars tend to be short-lived (15 years or less) because they’re prone to trunk canker diseases. They also have shallow, invasive roots and weak wood. Depending on the hybrid they may also produce cottony seed masses and root suckers.

Willows (Salix sp.) There are a variety of large fast growing willows planted as shade trees in home landscapes. This includes weeping willow (Salix spp.); the Austree willow, a cross between Hankow willow and white willow; and corkscrew willow. These are nasty trees with very aggressive roots that spread out as far as the tree is tall and farther. These roots proliferate where water is available and can damage irrigation lines, sewer lines, and septic system drain fields. Willows also have weak wood, shallow roots, and are prone to canker disease. All of this contributes to making them relatively short lived (30 years) shade trees.

While some trees are not well suited to the normal home landscape, most trees have some redeeming value. Willows will tolerate fairly wet soil, where many other trees won’t. Poplars and willows with invasive roots can be used to stabilize soil on river and stream banks. Fast growing trees can serve as temporary windbreaks until slower growing species have a chance to grow. However, the trees on my ‘worst list’ should usually be avoided. There are many other better choices for planting in your landscape.
Published: 10/1/2011 12:18 PM

WHEN THE BOUGH BREAKS, PREVENTING LIMB DROP

written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

I’d call it limbs falling out of trees, but the technical term is “branch failure. The winds last week in our region and elsewhere in the state led to a number of “branch failures.” When wind gusts blow and twist about tree tops, there’s always the chance of limbs and branches breaking. Rarely do limbs drop from trees for no reason. When the “bough breaks” and falls in wind storms, there are three very predictable reasons.

Past tree topping is at fault for many limbs that break from trees. When trees are topped the regrowth that develops are called water sprouts. These water sprouts are not strongly attached to the stem or branch on which they form. As they grow larger and heavier, they’re more and more prone to breakage in windstorms because their weak attachment can’t hold their weight.

This type of failure can be avoided by not making topping cuts on large tree branches and major limbs. If needed, tree height and crown density can be reduced with thinning cuts that retain a tree’s natural form and don’t leave stubs. With thinning cuts, branches are cut back to side or lateral branches that are at least one-third the diameter of the ones being removed. The growth that is stimulated by thinning cuts will be evenly distributed around the crown, in contrast to the vigorous, weakly attached water sprouts that result from topping cuts.

Wood rot is another problem that results from topping. A branch stub left from a topping cut never closes over, leaving the branch wood exposed and prone to invasion by wood rot fungi. Once rot invades the heart wood of a branch or trunk, it loses its structural integrity. Decayed branches are very vulnerable to wind breakage. Also, decayed branches provide poor support to branches that developed from water sprouts.

Wood rot is best avoided by making proper pruning cuts at the base of a branch, but outside what is called the branch collar. Treating pruning wounds with pruning paint or “wound dressing” materials will not prevent wood rot. In fact, these materials can actually encourage wood rot by sealing in moisture and excluding light, creating a better environment for wood decay organisms.

The third common reason for branch or limb failures are narrow or V-shaped crotch branch angles. These narrow angles are weak connections between two branches or limbs. The narrower the angle, the more poorly they’re bonded together. Stress put on these weak attachments by wind or ice can cause them to split. This is particularly true as the branches or trunks grow in girth, pushing against each other.

Certain trees, such as Bradford pear, green ash, and silver maple, are prone to developing narrow branch angles. However, other trees may also have narrow crotches due to poor training as a young tree. The best way to avoid problems is to refrain from buying trees that have already developed narrow crotch angles or trunks with forks. Forks are “co-dominant leaders” or competing leaders that have developed instead of a single trunk or “leader.”

When buying a tree, look for ones with good branch angles of 60 to 75 degrees. Avoid any trees with trunks that already have forks. Also, branches should be evenly distributed around the trunk, not all on one side or with multiple branches arising from one point.

Protect yourself from falling branches by never topping trees and by buying well-structured trees that won’t set you up for failure in the future.

Published: 1/21/2010 1:57 PM

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