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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?


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…


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Arborvitae is unarguably the shrub most commonly used to create an evergreen hedge, here and around the country. Gardeners who are tired of seeing arborvitae used over and over again for hedges, often ask me for a comparable substitute. There isn’t one. Arborvitae are the mainstay of evergreen hedges because they’re perfect for creating a “green” fence or boundary.

Arborvitae are a dense evergreen shrub with a long life. They have no serious insect pest problems in our area, as well as no common leaf diseases or blights. They’re tolerant of our local alkaline soils and don’t have any difficulty enduring our scorching summer or cold winter conditions. Their one drawback is that they’re subject to root rot if planted too deep or in poorly drained sites. Root rot can also be a serious problem if over-watered.

As a testament to their longevity, a drive around older areas of the Tri-Cities reveals how well arborvitae do in our area. However, you also might note just how big arborvitae can get. The species form of the eastern arborvitae (Thuja occidentalis), also known as the American arborvitae, can grow to a height of 60 feet and a spread of 10 to 15 feet.

Sixty feet is tall! No wonder people feel a need to chop them back when they get “too tall.” When those big old arborvitae were originally planted more than twenty or thirty years ago, there probably wasn’t much of a choice of cultivars. Many planted the species form to create hedges. Today, nurseries sell a variety of different arborvitae cultivars with different mature sizes, shapes, and even foliage colors. If you’re considering planting an arborvitae hedge, check out the different cultivars available from your local nursery or nursery catalogs.

Here are just a few of the popular ones:

Pyrimidalis – Smaller than the species, this cultivar still reaches a fairly lofty height, growing 20-30 feet tall and 5feet wide. Without shearing, it has a formal outline with bright green leaves that turn bronzy in the fall and winter.

Emerald Green (aka Smaragd) – Introduced in 1950, this cultivar has been around for a while. It has a narrow pyramidal form and grows to a height of 10-15 feet and a width of 5 feet, making it much smaller than the species. It has both good hardiness and heat tolerance.

Degroot’s Spire – This cultivar is a narrow columnar form growing 10-12 feet tall and 3-5 feet wide. The branchlets are spirally arranged giving the plant a natural spiral form. Foliage turns bronzy-purple during the winter.

Holmstrup – Holmstrup has also been around since the 1950s. It’s has a compact, slow growing conical form with a narrow, pyramidal shape growing to 5-10 feet tall and 2 feet wide. It stays dark green all year and is very hardy. (‘Miky’ is a cute little sport of ‘Holmstrup’ that’s shorter and even more compact.)

Techny – This slow growing arborvitae has a broad-based pyramidal form and grows to 10-15 feet tall and 6-8 feet wide at the base. It has dense, dark green leaves all year.

So if you’re considering planting an evergreen hedge, look for an arborvitae cultivar that’s the size and shape you need so you won’t be enslaved with regular shearing of your hedge. I’ve just listed some of the popular cultivars. Check with your local nursery to find out what different ones they have available.

Published: 4/2/2011 10:01 AM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

This past week I was asked to diagnose samples from a number of dying or dead arborvitae. Have you noticed them around the area? What’s causing this apparent epidemic? Before the samples were brought to the WSU Master Gardener Plant Clinc for diagnosis, the ailing shrubs had been variously mis-diagnosed with a variety of problems from spider mites to drought to “blight.” Various courses of action were taken, but the arborvitae continue to die.

Arborvitae are pretty much an insect and disease-free plant in our region. Because they usually thrive under local climate and soil conditions, they might even be considered a bit overused in our landscapes. However, when this virtually trouble-free shrub turns brown in the middle of summer the pronouncement is that “spider mites” or “blight” must be at fault. However, arborvitae are almost never troubled by spider mites. In fact, in my 25 years of diagnosing sick plants in this area, I have seen only one serious spider mite infestation on an arborvitae. There are a few other insect pests that can attack arborvitae, but these are seldom a problem here.

In our region, arborvitae are also rarely infected with leaf or tip blights caused by fungus diseases. These can be problems in wetter and more humid climates, but they’re seldom a problem here. When “blighted” arborvitae do appear, they’re usually in landscape situations where sprinkler irrigation is frequently wetting the foliage. Control is as simple as keeping water off the leaves.

Let’s get back to the current problem of dead and dying arborvitae. If arborvitae are such stalwart plants, why are so many of them turning up dead? A close investigation of the foliage doesn’t reveal any obvious problems. The unexplained death of the top of the plant points to root problems. Poor plant growth, die-back of individual branches, general discoloration of the leaves and the eventual death of the entire plant are the progressive symptoms of root problems.

That means we should turn our attention to what’s happening beneath the soil of the ailing arborvitae. It’s very likely that the problem is root rot. Believe it or not, root rot is a fairly common problem on arborvitae in our area. Even though many think that you can not overwater in our hot, arid climate… you can! The cause of failing arborvitae is very likely to be root rot, especially if they’re being watered heavily either with a drip system or sprinkler, or sometimes even both.

Root rot in landscape trees and shrubs is caused by a variety of different fungal pathogens found in the soil. Conditions that favor the development of root rot are poor drainage, saturated soil conditions, and warm temperatures. Other factors that contribute to root rot include planting root balls too deep, compacted soil, and mulch that’s too thick or matted to allow air movement.

Another factor that I often see contributing to a root rot problem is the type of soil in the original root ball of the arborvitae before it was planted. While some arborvitae are grown in pots in a well drained soil-less potting mix, some are grown in the ground and then dug up with clay soil around their roots. Clay is a “heavy soil” and not well aerated. It holds water tightly and stays wet longer than the sandy or loamy soils that predominate area landscapes. A problem can arise when we water for the typical sandy and loamy soils. These soils drain and dry out more quickly. Local landscapes are usually watered to keep lawns and other plants growing in sandy and loamy soils from drying out. When we do this, the soil in the clay root balls stays saturated… and can lead to root rot on plants.

The only way to tell if a plant has root rot is by looking at the roots. Healthy fine feeder roots are brown on the outside but have a white internal core and white tips. Root rot is indicated if the outer layer of the finer roots is soft, brown, and pulls off easily. Roots are obviously rotten if they’re soft, partially decomposed, and break off easily.

Once a plant with root rot starts showing death and dieback on top of the plant there’s not much you can do. Your attention should be given to those shrubs that aren’t exhibiting any symptoms yet or are in the initial stages of symptom development. Control might be as simple as not watering excessively and avoiding keeping the soil saturated. However, if the root ball is surrounded with clay soil, if the shrub is planted too deeply, or if the area has poor drainage, remedial action will be more difficult. These situations should be avoided before planting.

Dr. Linda Chalker-Scott, WSU Extension Horticulturist, and other horticulturists recommend gently washing the clay soil off the roots before planting so you don’t have that slow-draining clay soil around the roots. When this is done, you’re creating a “bare-root” tree or shrub. This should only be done in the fall or early spring when the plants are in a dormant stage.

Planting too deeply is a very common problem. The top roots of the root ball should be just below the surface of the soil. Planting them two or more inches below the soil level can lead to problems, especially from root rot. It’s best to dig your planting hole only as deep as the root ball and then plant the shrubs or trees slightly above the soil line, to allow for some settling after you thoroughly water the plant. If the area has poor drainage due to compaction or other factors beyond your control, you can make your planting beds into berms or raised beds.

If all remedial actions fail to stop successive arborvitae in a planting from dying, it’s possible that a particularly virulent type of root rot, called phytophthora root rot, may be involved. There are chemicals that can be applied to the soil to keep this fungus in check, but they’re extremely expensive and must be applied regularly. Once use of the chemicals is stopped, the disease can return. Before applying these chemicals, the disease should be positively identified. In our area, there are no local laboratories that can test for the disease. Samples can be sent to one of three labs in the region, but this is also a costly proposition.

So if you’re wondering what’s “attacking” and killing local arborvitae, the culprit likely lies beneath the soil. However, the real perpetrator is usually the person who planted them or the person who waters them… or both.

Published: 9/10/2005 11:40 AM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

I’m frequently asked about what plant will make a nice evergreen hedge. Of course the standard shrub I recommend for a hedge in our region is arborvitae. It can’t be beat. It’s tolerant of our summer heat, winter cold, and alkaline soils. It has few insect or disease problems. It grows relatively fast but doesn’t require regular pruning to keep it looking neat and tidy. Because it’s so good and relatively inexpensive to buy, it has become too ordinary for some gardeners.

Some gardeners want to stray from the beaten path and find less common, more distinctive plants for creating an evergreen hedge in their landscape. However, finding something different that performs as well as arborvitae is almost impossible. Nevertheless, here are some suggestions.

Well suited to our hot summer climate is the Rocky Mountain juniper (Juniperus scopulorum). Native to dry rocky areas of the western United States, it’s adapted to area conditions, doing best in full sun and tolerant of dry alkaline soils. It should be noted that most cultivars are relatively slow growing.

There are a number of upright cultivars of Rocky Mountain juniper that can provide a slightly different look than arborvitae. In selecting a cultivar, you will want to know its form, its approximate mature height and width, and its foliage color. A popular cultivar in the trade is ‘Skyrocket’ with blue-gray foliage. It has a very narrow form, growing to 25 feet tall and only three feet wide. While popular, it does have one drawback. When it reaches about 15 feet tall, the side branches may start to bend downwards. ‘Medora’ with blue-green foliage has a narrow, dense form growing to 15 feet tall and five feet wide. ‘Cologreen’ and ‘Greenspire’ both grow upright and narrow but have green foliage. There are also weeping forms. ‘Tolleson

s Blue Weeping’ is blue-green and has a weeping drooping form, growing to 20 feet tall and 10 feet wide. ‘Tolleson

s Green Weeping’ is similar but is dark green.

Another possible shrub for creating a screen or hedge is Leyland cypress (x Cupressocyparis leylandii). Very popular in other parts of the country, Leyland cypress is a fast growing evergreen with dark blue-green foliage. It grows in full sun or partial shade and tolerates a range of soils, including alkaline soils. Leyland does best with moderate fertility and adequate soil moisture. It has dense, feathery foliage on slightly pendulous branches.

One problem with Leyland cypress is that it grows big, up to 70 feet tall and 15 feet wide. This is not a sensible choice for an average size lot. However, it tolerates pruning and can be grown as a hedge. Keep in mind though that regular pruning of any hedge is labor intensive. There are a number of more suitable cultivars available. ‘Castlewellan’ has a dense crown with a conical to columnar form. It’s summer foliage is greenish yellow. ‘Moncal’ or Emerald Isle™ has a dense crown with bright green foliage arranged in flat sprays. With a mature height of 25 feet and a width of 8 feet, this cultivar is a better fit for home landscape situations, but it’s still a bit on the large size. There are also a number of cultivars with yellow to gold foliage including Golconda’, ‘Gold Nugget’, ‘Robinson

s Gold’, and ‘Gold Rider.’

A broadleaf evergreen that seems well adapted to our climate and tolerant of our soils is English laurel (Prunus laurocerasus), also known as cherry laurel. It’s an evergreen shrub that grows 10 to 20 feet tall and has shiny dark green oblong leaves. It grows best in moist, well-drained soil and can be grown in sun or partial shade. When planting it for a natural unpruned hedge, it would be best to pick one of the smaller growing cultivars, such as the popular

Otto Luyken

with a spread to 6-10 ft and a height of 3-5 feet or


which grows to 4to 8 feet tall and wide. While this plant is easy to grow and is also drought tolerant, there are two serious drawbacks to utilizing it in the landscape. First, the plant including the seeds is poisonous except for the ripe flesh of the berries. Secondly, this plant has become an invasive pest in the western part of our state where it has escaped cultivation and flourishes in forest understory growth. It’s responsible for out-competing native plant species and upsetting the ecosystem. Birds who eat the fruit have helped spread this weedy shrub. It’s already on the King county noxious weed list and should definitely not be planted in any regions where there are nearby forested areas.

If you ask me, arborvitae is still the best choice for an evergreen hedge in this area!

Published: 6/30/2007 2:47 PM


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

Last Saturday the Richland Riverside Rotary Club and WSU Master Gardeners celebrated 100 Years of Rotary by planting 101 arborvitae. They took on this monumental task in the Formal Garden being constructed in the Master Gardener Demonstration Garden in Kennewick. Not knowing how miserably wet and cold it would be, they picked Saturday morning to plant these shrubs donated to the garden by Riverside Rotary. While it wasn’t optimal weather for their personal comfort, it was a great time for planting trees and shrubs.

Early spring, while plants are still dormant and before new growth begins, is the very best time to plant trees, shrubs, and perennial plants in our region. That’s because the plants can start to grow new roots before they’re faced with hot weather and high demands for water. When trees and shrubs are planted during late spring or summer, they often become drought stressed even if there is plenty of water available. That’s because they haven’t had time to grow new roots to absorb as much water needed during the summer.

Thanks to the intrepid Master Gardeners and Rotary members, the 101 arborvitae have a good chance of establishing well and flourishing in the garden before hot summer weather arrives. However, timing isn’t the only key to planting success. The correct planting procedures are just as important as the time of planting. Let’s review the best way to plant trees and shrubs to insure success.

THE HOLE: It often makes folks feel good to dig a nice deep hole when planting a tree or shrub, but it’s the width of the hole that’s most important. Scientists have found that most woody plants don’t have deep ‘tap’ roots. The majority of roots absorbing water and nutrients are located in the top 12 to 18 inches of soil where they can get air and water.

A planting hole should only be as deep as the plant’s root ball. When you dig the hole deeper, the plant often settles after planting and ends up being planted too deep. The top roots radiating out from the trunk should be just below the soil surface. Instead of deeper, holes should be dug wider, at least twice as wide as the height of root ball. By digging a wide hole, the soil is loosened, making it easier for the roots to grow.

THE ROOT BALL: If the plant is ‘balled and burlapped’ with a root ball surrounded by soil and wrapped in burlap, the burlap should be removed. While old-time gardeners and nurserymen may tell you that you shouldn’t remove the burlap for any reason, horticulturists are now strongly recommending its removal. One reason for this is that burlap doesn’t decay as quickly as once thought, especially in our dry climate. Plus, much of today’s burlap is treated with copper, giving it a green tint. This copper treatment is intended to slow the decay of the burlap. Another important reason to remove the burlap is to look for any root problems, such as circling, girdling, or kinked roots or additional twine and burlap that might be hidden by the outer burlap.

More recently researchers are also recommending removing the soil around the root balls of balled and burlapped plants. This way you have a much better chance of finding serious root system defects that may be hidden by the soil. You also want to remove the soil because it’s often a heavy clay that’s very different in texture from soil in local landscapes. This big difference in texture impedes water movement and discourages root growth.

Dr. Linda Chalker Scott, WSU Extension Horticulturist recommends these steps when planting a ‘B&B’ or balled and burlapped tree or shrub:

1. Remove all wire baskets, twine, and burlap from the root ball. Do this on top of a tarp to make it easier to transport the root ball remnants elsewhere.

2. Remove the soil from around the root ball, using a water bath or hose. Use your fingers to work out clumps of clay from between the roots.

3. Look for and prune out defects in the freshly bared root system. Be sure to keep the roots moist during the procedure. Work in the shade or on a cool, cloudy day if possible.

4. Dig the planting hole, making it only as deep as the root system and at least twice as wide. The hole will resemble a shallow bowl, not a deep pit. If necessary, mound the soil in the bottom of the hole to help support the tree when planting. Arrange the roots radially in the hole.

5. Backfill with native soil… no soil amendments should be added to the hole.

6. Water in thoroughly, sticking the hose right into the loose dirt. Once all air pockets are out, let the water settle and then use excess soil to bring the soil to the correct level. Use your hands, not your feet, to firm the soil around the base of the tree. Apply an appropriate fertilizer. Mulch the entire planting hole with at least four inches of organic mulch, keeping an open buffer zone between the trunk and the mulch. If needed, stake the tree low and loose with three stakes.

Dr. Chalker Scott admits that, ‘This method is radically different from historically accepted practices. Yet recent and ongoing research demonstrates that bare-rooting B&B trees leads to substantial increases in tree establishment and survival. Investing the time to prepare and install trees properly will pay future dividends of reduced maintenance and mortality for the lifetime of your landscape.’ Following these guidelines will help insure tree and shrub survival in your landscape.

Published: 4/8/2006 11:22 AM



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