Dry and shriveled leaves are indications of drought stress.

Drought Stress to Trees and Shrubs

Drought is a meteorological term for lack of precipitation over a long period of time. With our traditionally dry summers, drought is an issue through the months of June to mid October. This Spring we also had a longer than normal period without precipitation.

Plants can suffer from drought stress any time they receive less water than they need. Water is essential to the normal maintenance and growth of all plants. It moves into the plant roots from the soil and is transported up through the water- conducting vessels in the branches, stems, and foliage to all the plant cells. Eventually, the water evaporates from the tiny breathing pores in the leaves.

When plants don’t receive adequate water, the water pressure in the cells can drop. Plants will begin to wilt, stop growing, become discolored and stunted, drop their leaves and fruit, or eventually starve and die. Other visible signs are discoloration to the edges of the leaf and the size of the leaf can be smaller than normal. Also, insect and disease problems are attracted to drought stressed plants, and plant dieback or death can occur more rapidly during this period.
Most plants in our area need water in the summer and early fall. Proper irrigation is the most common method to correct drought situations. Mulching the drip-zone of trees and plants will help conserve the soil moisture and it will also improve the soil structure. Proper irrigation can be accomplished any time of the day, but it is more efficient to water early in the morning or later in the evening, because evaporation is less. The rate of application should be no more rapid than the rate at which the soil can absorb it. Give your plants the equivalent of 1” of water per week during dry periods. When temperatures rise about 90º you will need to water more. Remember to conserve water where possible, because it is a valuable resource which is becoming more scarce.

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Oregon Garden’s Signature White Oak Gets Needed Surgery

At the age of 400, you’d probably expect to begin to feel some wear and tear. Well, the 400-year-old Oregon White Oak, which is the signature oak at the Oregon Garden, in Silverton is no exception. It has a large branch that was failing and which could split the tree if it fell. Over the Earth Day weekend, the Portland based company, Collier Arbor Care, volunteered to perform some limb surgery which it hopes will send the tree on its way to another 400 years of life.

Arborist John Dale, of Collier Arbor Care examines a trunk bulge on the 400 year old signature white oak tree at the Oregon Garden in Silverton

“These are exceptional trees, and I see no reason why it can’t live another 400 years. After all, it was an adult when Lewis and Clark made their journey here, and it would be a shame to lose that kind of link with the past,” said Terrill Collier, president of Collier Arbor Care, who chairs the Oak Grove Committee that helps manage the garden’s oak grove.

On Friday, April 16, a crew of three Collier arborists began a two-day process of cabling together limbs in the expansive canopy to mechanically reduce the potential of the tree splitting under the onslaught of winds, ice and snow over the next decades.

Collier’s crew installed six cables. The process calls for using a pulley system to temporarily bring limbs closer together to be cabled. Then a threaded rod is put through the branches to be cabled. Eye nuts are screwed onto the threaded rods. A cable is attached to the eye at the end of each threaded rod, the pulley is released and the newly installed cable mechanically holds the limbs in place.

“I know all this sounds a little technical and may be hard to visualize, but it all makes sense when you see how it’s done,” said Collier whose firm has provided pro-bono care for the tree for the last four years. A thorough pruning and shaping of the tree took place three years ago, “and you can imagine what a job that was when you see how big this tree is!” said Collier.

The garden’s signature Oregon White Oak is part of its oak grove, which Collier’s committee hopes to restore to its natural state. Currently it contains blackberry bushes and exotic or non-native plants.

“The Oregon White Oak is one of the few deciduous trees in Oregon which live this long. It’s a really special tree, and I wouldn’t be surprised if there were quite a few others around in this age range,” Collier said.
Collier’s firm also is performing volunteer maintenance on Vancouver’s Old Apple Tree, thought to be the oldest living apple tree in the Pacific Northwest.

(Left)Trunk of a mature Katsura Tree (Top Right) Fall brings a spectacular show of bright yellow foliage with the scent of cotton candy (Bottom) Right) Mature Katsura Tree

From left, Peter Daves and Terrill Collier of Collier Arbor Care, Kim Silva and Keli Yeats of Friends of Trees, and homeowner Jim Cilek, with his dog Cinnamon.

Featured Tree: Katsura (Cercidiphyllum japonicum)

Looking for the perfect tree for the open space in your landscape? Wanting a shade tree with four-season appeal without the massive size of oaks or maples? The Katsura may be the tree you are looking for.

Introduced from China and Japan, the Katsura has a maturity height and width of approximately 40 to 60 feet. The growth habit when young is pyramidal and rounded when matured. The leaves average 2 to 4 inches long and heart shaped. Young leaves emerging in the spring are purplish, fading to a light blue green in the summer. In the fall the Katsura puts on a spectacular show of bright yellow foliage with an aroma said to be that of cotton candy.

The Katsura is multi-stemmed (more than one dominate trunk) or a single trunk with dominate side branches. The bark is shaggy and is very showy during the dormant season. Also available is a gracefully weeping variety.

The Katsura is a low maintenance tree with no serious insect or disease problems. Once established in the landscape the Katsura tree will be admired and appreciated for many years.

Collier Arbor Care Supports Friends of Trees in Hillsdale Effort

On March 13, thirteen Collier Arbor Care employees showed up to assist the Friends of Trees tree planting effort in the Wilson Park areas of HIllsdale. In this joint effort with members of the Friends of Trees, 26 trees were planted in the Hillsdale and Marquam neighborhoods. Since 1989, Friends of Trees has distributed more than 260,000 free trees and shrubs.

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