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THE SCIENCE OF FALL LEAVES

GARDEN TIPS – Written by Marianne Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Published October 30, 2016

Fall is my favorite season of the year. Growing up in the northeast part of the country, I have always been enthralled with trees changing color in the fall. The bright red, orange and yellow colors of autumn are marvelous. I can recall collecting the prettiest leaves on my way home from elementary school and bringing them to my mother.

After I became a science nerd, I wondered how this miracle of nature happened each year. It is because fall’s shorter days and cooler weather cues deciduous trees (ones that lose their leaves) that winter is coming. The leaves stop making carbohydrates via photosynthesis. Chlorophyll, the green pigment in leaves essential to photosynthesis, starts to break down. As the chlorophyll dissipates, the yellow and orange pigments already in the leaves become visible. In addition, anthocyanin pigments may develop in the leaves of some trees, resulting in red and purple leaf colors.

A variety of weather conditions influence the development of fall color. Fall colors will be their brightest when fall days are sunny and nights are cool and dry. Cool, dry conditions speeds the breakdown of the chlorophyll. Sunny weather promotes the production of the anthocyanins. If trees are drought stressed going into fall, the development of fall color may be delayed or can also result in early leaf drop.

Natural leaf drop is also part of the fall leaf phenomenon. Leaf drop occurs because the shorter, cooler days also prompt a layer of cells (called the abscission layer) to form where the leaf is attached to the twig. This layer of cells blocks the flow of water and nutrients in and out of the leaf. As the leaf begins to decline or senesce, it starts to produce ethylene, a plant growth regulator. Ethylene stimulates the production of enzymes that break down the cells in the area where the leaf is attached to the tree. This weakens the attachment and the leaf falls from the tree.

Some species of trees, such as oaks and beech, do not shed most of their dead leaves all at once in autumn. Instead, the leaves drop gradually over the winter or when the new buds begin to grow in the spring. This is called marcescence. Occasionally, marcescence occurs on many other types of trees as a result of a very early hard freeze. An early freeze surprises trees before the abscission layer has had time to form.

One thing you might not know is that needled evergreens also shed their “leaves” or needles in the fall, despite the descriptive epithet of “evergreen.” Each year the oldest needles on evergreens, such as pines, turn yellow, orangish-tan, or brown and drop from the tree. In most years, the change in color and drop of needles happens gradually and goes unnoticed except for the piles of needles beneath the trees. Other years, it can happen all at once and cause concern when it is observed.

In our area this phenomena is most often noticed on long-needled pines, such as ponderosa pine and white pine, as well as on arborvitae. If you note it and are concerned, check to see if the yellowing or browning needles are the older growth towards the inside of a branch. If the tips of branches on the outside of the tree or shrub are turning yellow or brown, there may be a problem worthy of concern.
Despite recent rainy weather, my two red maple hybrids, a Marmo maple and an Autumn Blaze maple, are turning delightful shades of red and orange. How about the trees in your yard?

FOREST BATHING AS A GARDEN TREND?

GARDEN TIPS – Written by Marianne Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Published October 9, 2016

I like to keep up with the most current gardening trends so I am always interested when the Garden Media Group (GMG) releases its Garden Trends Report for the coming year. For the next month or so I will share a few of the 2017 trends with you.

One of the 2017 trends GMG notes is “forest bathing.” Wait! It is not what you are thinking. This is not about hauling tubs out into the forest and taking a bath. Forest bathing or shinrin-yoku is the term used to describe this new fitness trend. It simply involves spending more time with nature to nurture all of our senses, reduce stress, and increase well-being. It is a purposeful practice of immersing yourself in nature. According to GMG, forest bathing is a “cornerstone of preventative health care and natural healing in Japanese medicine.”

To be honest I had never heard of forest bathing until I read this report so I did a little research. Forest bathing was started in the 1980s in Japan and is about taking leisurely hikes or walks in natural areas with the purpose of breathing fresh air, relaxing, and connecting with the natural world.

While this might seem like nonsense promoted by nature fanatics or flower children of 1960s and 70s, it is backed up by scientific research. It is not news that spending time in a wooded area or a garden can significantly reduce stress by lowering the cortisol, one of the hormones associated with stress. Chronic stress is associated with the increased risk of heart disease, high blood pressure, weight gain, deterioration of cognitive functions. Research has shown that lowering cortisol and other stress hormones can improve your immune system.

I knew that plenty of research is available documenting the health benefits of interaction with nature in green spaces like gardens, parks, and forests, but I did not know about phytoncides. Phytoncides are natural chemicals released by needled evergreens. Research indicates that when these chemicals are inhaled on a regular basis, they may significantly improve the human immune system.

My research into forest bathing revealed that there is a U.S. organization (www.shinrin-yoku.org) that promotes shinrin-yoku therapy. Who knew? This organization offers three hour therapy walks and seven day immersions in California. The Association of Nature & Forest Therapy Guides & Programs (www.natureandforesttherapy.org) trains and certifies therapists or guides from other parts of the country so the practice of forest bathing can be spread to other parts of the country.

I am not sure we need to practice forest bathing in an actual forest. I bet we can gain similar benefits by spending time in our gardens, tending the plants, hearing the hum of honeybees and other insects, and appreciating nature. Folks without a garden should make a habit of visiting the Master Gardener Demonstration Garden located behind the library at 1620 South Union. This almost three acre garden is a delight any time of year.

In the Master Gardener Demonstration Garden you can discover how restoring it is to sit for a while on the bench in the Bird & Butterfly Garden or relax in the Serenity Garden, listening to the sounds of nature. Of course, if you want to breathe in the phytoncides of an evergreen forest, you will need to drive to the Cascades and take a hike in the woods. Make it a leisurely hike and breathe deep while amongst the trees. Ahhh!

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…

TREES ARE GOOD FOR US

GARDEN TIPS – Written by Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Published May 15, 2016

I hope celebrated Mother’s Day with some pretty flowers or plants. They can help moms live longer! Recent research at Harvard University indicates that higher levels of green vegetation are associated with decreased mortality in women.

Harvard researchers found that women living in the study areas with the highest levels of greenery had a 12 percent lower mortality rate. The lead researcher attributes this lower mortality rate due to less air pollution, greater physical activity, more social interaction, better mental health, and decreased depression. This is proof that green spaces, including parks, street trees, and even turf, are important to our health and well being.

Too stressed out to think about it? Trees and green spaces can help. A university study in Scotland measured cortisol levels (the principal human stress hormone) in both men and women over the span of a day. Individuals experiencing everyday life stresses experienced lower cortisol levels if they were surrounded by green spaces.

If you find these benefits too vague, consider that trees and green spaces provide real economic value to our communities. A 1990 study in Sacramento revealed that residents whose homes had shade trees planted on the west and south sides of the houses saved an average of $25.16 over the summer in cooling costs. While not impressive on an individual basis, the savings were significant considering the large number of homes in Sacramento.

A study in Portland found that street trees added an average of $8,870 to a home’s sale price, as well as raising the value of nearby houses. Those conducting the study extrapolated these numbers to include the entire city and found that Portland street trees have a capital value of $1.1 billion and provide an annual benefit of $45 million. Considering the increased property tax revenues due to the increased in property values realized from homes with street trees, the trees bring in $15.3 million every year in revenue. This is greater than the estimated $4.6 million annual maintenance costs of the trees. This has Portland seeing “green” and as a result they have focused their efforts on planting many more street trees.

Need more convincing? Consider that studies have shown that paved streets shaded by trees last longer and needs less maintenance over time, saving potentially up to 60 percent of repaving costs over 30 years. Other documented benefits of trees and green spaces have shown that they improve air quality by trapping pollutants and particulates, decrease asthma and other respiratory problems, increase physical activity levels, improve mental well being, lower stress levels, provide protection from UV radiation, reduce noise pollution, calm drivers and slow traffic. Wait, there is more. Trees store carbon, reduce the heat island effects in cities, reduce violence and crime, and increase a sense of community.

Kudos to the Cities of Kennewick, Pasco, and Richland for their dedication to improving our communities with trees and green spaces. All three cities have been recognized as a “Tree City USA” by the Arbor Day Foundation. The award acknowledges them for addressing the core standards of urban forestry management which are maintaining a tree board or department, having a community tree ordinance, celebrating Arbor Day, and spending at least $2 per capital on urban forestry. All three cities celebrated Arbor Day last month and worked with volunteers to plant trees in our city parks and along our streets.

A GOOD OFFENSE THE BEST DEFENSE AGAINST TREE BORERS

GARDEN TIPS – Written by Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Written December 27, 2015

Now that we have almost closed the book on 2015, let us reflect a bit on the extraordinary weather of this past year and years past. It is no surprise that the summer of 2015 was the hottest on record in the region with a total annual precipitation of 3.72 inches. That is not much considering that 9.16 inches of moisture were lost through evapotranspiration (ET) during the month of August. Plus, some areas experienced limited irrigation water.

This extraordinary year was compounded by the fact that until 2015, 2014 was the hottest on record with 3.44 inches of precipitation, a total ET of 9.02 inches in August, and an unusually mild December. Also consider that 2013 was the 2nd hottest summer on record until 2015 with a total annual precipitation of 2.79 inches. Plus, the summer of 2013 was the 6th year of summer weather with near or above average temperatures.

That is a great deal of summer heat. Heat stresses plants, especially ones not well adapted to our hot summer climate. Heat stress is compounded by drought stress that results from limited irrigation water or improper watering practices. Drought stress may also be inflicted on a tree due to a lack of an adequate root system, physical injury to the trunk, restricted or girdling roots, compacted soil, or other factors that affect the tree’s ability to absorb or transport water to the top of the tree.

Stress on trees makes them more vulnerable to attack by certain insects, especially boring insects. As a result of the several years of summer heat stress that local trees have endured, we are seeing an increasing number of wood borers attacking local ornamental trees.

Even if a tree looks fairly healthy to you and me, it may become fodder for borers because it is stressed. Stressed trees are more vulnerable to attack by borers because stress causes them to produce volatile chemicals, such as terpenes, that attract boring insects.

In addition, some borers (such as bark beetles) will emit an aggregation pheromone (a chemical compound that elicits insect behavior) once it locates a stressed tree. This insect pheromone lets other bark beetles in the area know of a stressed tree’s presence. One bark beetle might not significantly harm a tree, but a bunch of them feeding spells trouble.

Once the volatile chemicals emitted by the tree and the aggregation pheromone gets a gang of bark beetles to the tree, they still have to get under the bark. As they start to eat their way into the tree, the sap pressure in a healthy tree will often drown or push them back out. However, in a stressed tree the sap flow is lower and they can successfully eat their way in.

The quote of “the best defense is a good offense” may or may not be true in sports, but it is very true when it comes to protecting your trees from boring insects. Keeping a tree healthy is not just its best defense against borers, in many cases it is the only defense.

We no longer have the long-term residual insecticides that were once used to protect trees from borers. Insecticide applications as a spray to the trunk are generally not a good “offense” and even the systemic insecticides applied to the soil or injected into the trunk are only effective against a few types of borers.

Hopefully in 2016 we will not experience another summer of extraordinary heat and limited irrigation water. If we do, make every effort to keep your trees healthy and “unstressed” to protect them from attack by borers.

AVOIDING HAZARDOUS TREES

GARDEN TIPS – written by Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Written November 29, 2015

You probably have heard about the many trees that came down around our state in the windstorm last week, but you may not have heard about one tree in Spokane that snapped off and speared the house below. It entered the roof, went through the crib of a six-week old baby, and stopped only when it reached the basement floor. Thankfully, the baby was with his mother who was in the kitchen fixing dinner and the rest of the family was safe too. This hazardous tree story literally hit home for me because that little baby is my grandson.

I have talked often about not topping trees, but this story stresses why it is important to prune trees properly and to periodically assess large trees for the potential hazard that they may pose.
What qualifies a tree as “hazardous?” A tree is considered “hazardous” when all or part of the tree could “fail” and damage a “target,” such as a building, a vehicle, or people. Common failures are the breaking off of a tree limb, a tree splitting apart, or a tree uprooting and falling over.

There are a variety of reasons for failures including wood decay from past topping, other bad pruning cuts, or injuries to the bark and trunk; a lopsided crown; competing central leaders or main branches that are weakly attached at a less than 45 degree angle; the severing within the drip line of more than 50 per cent of a tree’s root system; and the development of significant girdling roots at the base of a tree.

The failure of a small tree is usually not significant, but the failure of a large tree can be catastrophic. When I first moved to this area in 1980 we didn’t have many large mature trees in our home landscapes, now there are many more. This is good, but it has also increased our potential for hazardous trees.

If you have a larger older tree, I urge you to check for any signs of potential failure in your shade trees and then consult an ISA certified arborist if you think there might be a problem. A certified ISA (International Society of Arboriculture) arborist can give you reliable advice regarding your tree and its health.

Signs of potential tree failure include:
– trees that have been topped in the past
– a tree that is leaning
– a tree with multiple trunks or with competing leaders
– trees with lopsided crowns
– trees with dead or broken branches
– trees with dead areas of trunk or signs of wood rot

If you have smaller tree that will grow into a big one, also consider having an arborist check it for any corrective pruning that is needed to avoid future problems. It is better and less expensive to take care of these problems when the tree is young.

It is possible that a consultation with an arborist prior to last week’s extraordinary wind event might have avoided the damage to my family’s home, the deaths of several people, and the property of many others, but there is no way to know for sure. Hindsight is always better than foresight.

Hiring an certified to take corrective action before a tree becomes a hazard is not inexpensive, but it is much less costly than having a tree come through the roof your house and potentially harming your family. A search of the yellow pages in the phone book or on-line will help you find a qualified ISA certified arborist. Please do this now before the next big windstorm.

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?

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