blooming flowers climber in tree to prune beneficial mushrooms close up of lady bug on leaf japanese maple being pruned
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The Arbor Advisor
> My Tree is Too Big!
> Phythophthora — A Wet Soil Disease
> Featured Tree: Oregon White Oak
> Meet the Plant Health Care Department

Phytophthora Root Rot

What do the Irish potato famine, sudden oak death and your dying rhododendron have in common?

Orford Cedar
				hedge dying from Phytophthora Orford Cedar hedge dying from Phytophthora
A sign
				of disease A sign of disease: reddish-brown discoloration with a sharp line separating healthy white tissue

These serious plant problems are caused by a root rot disease called Phytophthora. Our naturally wet rainy climate and heavy clay soils create ideal conditions for root rots to flourish and damage susceptible plants. While disease management is possible through a combination of cultural, organic and fungicidal treatments it is often better to replace the dead plant with a swamp plant that can tolerate the conditions or turn the area into a pond. There are many hundreds of plant species that are attacked by Phytophthora root rot — here are the facts:

Plants Affected

Ornamental trees: cherry, dogwood, holly, madrone and oak.
Conifers: arborvitae, cypress, juniper, Port-Orford cedars, Pines, true firs, yew.
Fruit trees: Apple, cherry and peach.
Shrubs: Andromeda, azalea, boxwood, heather, rhododendron, salal.


Diseased plants are commonly found in heavy clay soils and poorly drained areas of the landscape. Affected plants will have reduced vigor and growth, yellowing of the leaves, then wilting, rapidly turning brown, resulting in death of the plant. Infected trees may decline slowly over a several year period or they may suddenly wilt and die rapidly after the first warm weather period. Some species of Phytophthora will attack above ground portions of plants such as branches of rhododendrons or tree trunks as in sudden oak death.



  • Avoid sites that drain poorly or are periodically flooded.
  • Improve drainage by installing underground drains or breaking up hardpans and compacted soil.
  • Regulate water usage, do not over irrigate.
  • Remove infected plants and infected plant parts.
  • Install plants that are resistant to Phytophthora — plants that are adapted to swampy conditions. Some examples include; tupelo, aspen, serviceberry, sweet bay magnolia, and red twig dogwood.


A preventative application of beneficial mycorrhizae has been demonstrated to help protect roots from Phytophthora infections.


Use of approved fungicides can help manage Phytophthora but are seldom effective in reviving plants that have advanced symptoms and are wilting. Fungicides are most effective when combined with the cultural practices described above.

This tree has outgrown it’s location — blocking the window and doorway This tree has outgrown it’s location — blocking the window and doorway
This tree was Crown Thinned and Crown Reduced This tree was Crown Thinned and Crown Reduced

Two Remedies for "My Tree’s Too Big"

We often get told by clients that they have a tree that is too big and “something” such as "topping" needs to happen to solve the problem. Since topping is not an acceptable way to reduce tree size, we need to understand what the goals and objectives are behind the client’s request to reduce tree size. Topping creates ugly, hazardous and unhealthy trees. If topping does not kill a tree then it will stimulate a rapid and unwanted sucker re-growth as well as allowing decay to rot the insides of a tree. Many people want trees topped or removed because they are too big. Trees occasionally drop large branches or fall (usually because of storm conditions or poor health), but not because they are too big. If you feel your tree is unsafe, have one of our arborists do a hazard tree evaluation. If your tree has truly become too big because it is growing into your house, raising the sidewalk, blocking your view of Mt. Hood, or numerous other reasons then consider the following options:

Remove and Replace

If a tree is truly in the wrong place consider removal. We remove weeds because they are in the wrong place or tear down old buildings when they no longer contribute to property values. It is often better to remove a tree than to keep it unnaturally small by improper and repeat pruning. Plant the right tree in the right place. Replace it with trees that are genetically programmed to grow and stay smaller. Trees such as Styrax, Stewartia, dogwoods and Japanese maples are but a few examples of beautiful small trees.

Prune the Tree

Our skilled arborists can prune your trees to make many of your tree problems (and fears) magically go away. Selective pruning can reduce the bulk of your tree, allowing more sunlight to penetrate and wind to blow through a tree — making it safer. Our arborists know specific pruning cuts that will make your trees safer, less massive and they know when to quit, so as not to over prune.

We prune trees in accordance to the American National Standards Institute (ANSI) A-300 Pruning Standards. Each tree pruning estimate includes an explanation of the terminology and the different types of pruning in the standard.

The following are types of pruning that can be done to keep your trees smaller and safer:

  • Crown cleaning removes the dead, diseased and dying branches from your tree.
  • Crown thinning selectively removes a specified percentage of branches and foliage (but no more than 30%) — reducing bulk, increasing sunlight penetration and decreasing wind resistance.
  • Crown Reduction reduces the height and width of your tree by a specified amount. This type of pruning shortens long branches by cutting a long branch back to a shorter side branch (commonly called drop crotch pruning) thus shortening the length. When done properly this type of pruning is very labor intensive and will usually need to be repeated at regular intervals. When crown reduced, an 80-foot shade tree will only have a 5 to 8 foot reduction in height and width due to limiting the removal to 30% of the foliage of the tree. Crown reduction is not topping nor is it heading cuts.
  • Crown raising removes lower branches to a specified height, such as removing branches off roofs or away from streets and sidewalks.

Just because a tree is “big” does not mean it is unsafe. Trees are big by their very nature; after all they are the tallest, most massive and longest lived organisms on the planet. True tree lovers will appreciate a tree’s greatness by its size, age and species. To find out how to manage your tree, give us a call. You may find that it is just a youngster with more growing ahead. Or, it may be the biggest and best in your neighborhood — you might just want to maintain it that way.

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The Plant Health Care Team The Plant Health Care Team: Tom Townsend, B.S., Certified Arborist; Kellee Boyer, B.S.; George Clymer; Bob May, Certified Arborist; Chris Miller, A.S. Certified Arborist; and Bruce Colman, B.S.

Meet Collier Arbor Care's
Plant Health Care Department

The Plant Health Care Department has come a long way since 1937 when Ray Collier founded the company with one spray truck and his ambition. Our 6 Plant Health Care Technicians diagnose and treat pest problems with modern environmentally friendly products, up to date scientific knowledge and the latest in pest management techniques that past generations did not have. The state-of-the-art trucks that our employees use give us the ability to deliver the correct product or technique necessary to protect your valuable landscape plants from pest attack.

The most important part of the department, our Plant Health Care Technicians, have the education, technical training and practical experience that is necessary to deliver quality pest management services to your landscape. Our Technicians have a combination of college degrees and multiple years of experience within the Horticultural field. Three of our Plant Health Care Technicians are certified arborists, and the others are currently studying to receive certification.

My Favorite Native Tree: Oregon White Oak

By Terrill Collier

Oregon Garden Signature Oregon White Oak (Quercus garryanna) The Oregon Garden Signature Oregon White Oak (Quercus garryanna)
An Oregon White Oak An Oregon White Oak
The jumping oak gall
The jumping oak gall forms BB-sized galls that drop in the Fall. The galls jump around like Mexican jumping beans due to the activity of the enclosed larva

A large beautiful native tree, the Oregon white oak (Quercus garryana) can achieve heights of over 100 feet. Oaks are known for their massive size, long life and characteristic rounded crown — the Oregon white oak is no exception. The dark green leaves grow up to 8 inches in length with deeply rounded lobes. The leaves and branches often have “oak apples” or galls caused by the gall wasp insect.

The Oregon white oak has the longest north-south distribution among the western oaks occurring from Vancouver Island, British Columbia to southern California. It is adapted to grow on a variety of sites ranging from wet to dry and from sunny to partial shade. The Oregon white oak is an extremely valuable wildlife tree. The acorns are used by many animals including squirrels, and woodpeckers. Its large branches provide resting spots for many bird species and cavities in the wood provide homes for the Acorn woodpecker.

One of the largest Oregon white oaks in the world is the Signature oak at the Oregon Garden. It is nearly 100 feet tall, 125 feet wide and 89 inches in diameter. In 2004 our Company received the Excellence in Arboriculture award from the Tree Care Industry Association for our pro-bono pruning and cabling work on this 400 year-old tree.

Although not widely utilized by the Ornamental industry, the Oregon white oak is a wonderful tree to plant if you have the space. Its large spreading crown creates a cooling shade and its gnarly, twisting branches are striking. If you are blessed with a Garry oak in your yard, do not plant a lawn underneath and heavily water. Oaks are very susceptible to this radical change in root environment and root rots like Armillaria can attack and kill the tree.

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