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The Arbor Advisor
> Spur on Growth with Root Zone Invigoration
> Put a Stop to Dogwood Disease
> Espalier — Create a Living Sculpture
> Featured Tree: Star Magnolia

Be on the Lookout for Dogwood Anthracnose Dogwood leaf showing signs of disease. Signs of infection on Dogwood leaves.

One of America's favorite native trees is under siege by a destructive disease first discovered over 20 years ago. Dogwood anthracnose (Discula destructiva) is a devastating fungal disease that infects flowering dogwoods in both landscapes and forests. Most common in landscape dogwoods, it has also taken a toll on our native Pacific dogwood (Cornus nuttallii).

Dogwood anthracnose can affect all flowering dogwood species. The most susceptible is the Pacific dogwood followed by the eastern flowering dogwood (Cornus florida). The kousa dogwood (Cornus kousa) is considered mostly resistant.

Symptoms usually appear in May, but the infection process starts earlier during wet weather. Common symptoms are large, brown, irregular shaped blotches with dark brown to purple margins on the leaves. Infection often begins at the tip, spreading down the mid-vein, producing a wedge-shaped appearance. Diseased leaves are usually shed, sometimes defoliating the tree. Infected twigs have sunken cankers that are tan to brown with purple borders. The cankered spots eventually enlarge and girdle the twig, resulting in small branch dieback. Anthracnose weakens the dogwood defenses and allows other diseases like Armillaria and Phytophthora root rot to kill the tree.

The disease overwinters on dead twigs on the tree, and dead leaves on the ground. Diseased leaves and twigs discharge millions of spores, causing infection in spring on succulent new leaves and stems during wet, mild weather. Dogwoods planted in shady, moist conditions and high rainfall areas get worse infections.

Disease Management
  • Plant disease resistant kousa dogwoods.
  • Prune and destroy infected twigs, rake and destroy fallen leaves throughout the year. Thin tree canopy for circulation.
  • Protect leaves from infection with three to four preventative fungicide treatments in the spring starting at bud break. Treat with an organic copper or an approved systemic fungicide.
  • Provide a healthy growing condition by mulching the root zone and by using the Collier Arbor Care Soil Health Care program.
  • Call a Collier Arborist to recommend a program to keep your dogwoods healthy.

Featured Tree: Star Magnolia

Close up of Star Magnolia blossoms.

The star magnolia is a small ornamental tree with an oval shaped crown, growing to a height of 15-20 feet. It is best known for its large, fragrant, star shaped flowers that appear in early spring before the leaves. The large fuzzy buds, when opening, will be pink hued before fading to a pure white flower. Unlike the better known evergreen southern magnolia, the star magnolia is deciduous and requires less maintenance with much easier leaf cleanup. The leaf is a pleasant dark green in the summer with a nice yellow fall color. These magnolias produce a reddish-green, knobby aggregate fruit about two inches long that opens in early fall revealing brilliant orange seeds.

Close up of Star Magnolia blossoms.

This well behaved magnolia is a native of Japan. It is a very attractive accent plant, spectacular when in full bloom against a dark background. They like well drained, organic, acid soil, but tolerate clay soil. As with most trees, provide a good layer of mulch around the roots. They grow best in full sun to partial shade. Typically magnolias require only a modest amount of pruning, usually thinning to keep an open airy shape. They also make a good tree in lawn areas provided you keep a large grass free, mulched area around the trunk. This is basically a trouble free tree with no serious pests.

This spectacular magnolia is a perfect flowering tree for small properties as it remains compact in height for many years and for its large star shaped flowers that bloom in profusion throughout the crown.

Finished root invigoration shows mulch around base of tree.
The finished root area is loaded with nutrients to promote healthy
tree functions.

Supersonic air tool is used to aerate soil and add health nutrients.
In Root Invigoration, soil is loosened with the supersonic air tool to
relieve compaction.

Give Plants a Boost with Root Invigoration

Do you have a favorite or specimen tree you want to keep healthy? Or do you have a tree or shrub in the landscape that is not growing vigorously? Root and soil disorders are the leading causes of premature landscape plant decline. Compacted soil, girdling roots, root rots, lack of organic matter, poor nutrition and poor or heavy clay soils can all contribute to poor plant performance and ill-health.

Solution to unhealthy plants: Our root invigoration program!

This unique plant invigorating program combines our most beneficial plant health enhancing programs into a comprehensive package designed to invigorate your plants root system. By relieving soil compaction, improving soil aeration, adding organic compost and nutrients, we stimulate healthy soil biological activity and conditions for vigorous root growth.

What does root enhancement achieve?

Stimulating root growth allows some declining trees and shrubs to recover their health over time or assists in maintaining a favorite plant's health and beauty. A healthy root system promotes all other tree functions such as: trunk growth, defense, fruit, flower and leaf production.

Steps in root zone invigoration

  • Diagnosis: a Collier arborist will diagnose the problems and offer recommendations for plant, root and soil improvement.
  • Soil test for nutrient and organic matter levels.
  • Loosen soil and relieve compaction with a supersonic air tool.
  • Add composted mulch, organic nutrients and beneficial mychorrhizae to root zone with the aid of the air tool.
  • Finish with a two to four inch layer of mulch (not covering the trunk) and a compost tea application to inoculate soil with beneficial microbes and root stimulants.

What are the Results?

Each plant is unique, but typically within a few weeks new root growth will be stimulated, and continue to grow in the improved soil environment. The next growing season or flush of growth the plant will have increased growth and density, healthier looking foliage and a more lively appearance. Due to a stronger root system and improved nutrient availability, the treated plant will have better defenses and increased longevity.

Questions about your soil quality? Call today and let Collier Arbor Care help with a free Soil Health consultation!

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Create a Living Sculpture with Espalier

An "espalier," (pronounced "es-PAL-yer") is the ancient practice of training plants to grow in a flat plane against a wall, fence, or trellis. The practice originally was used in the old world to conserve space. The English located espaliered fruit trees against a wall with a southern exposure for cold protection and early fruit ripening. Today, espaliers are often used for decorative accents in the landscape or for growing grapes or fruit trees. An espalier is a living sculpture in the garden and is especially effective against a blank wall to relieve the monotony. With landscape spaces around homes becoming smaller, an espaliered plant has considerable appeal.

Diverse landscape
An example of Espalier — the flexible branches of a pear tree have
been trained in a horizontal pattern against a flat surface.

Diverse landscape
Liven up a large, flat plane with espalier as with this camellia. Almost any
plant can be used, but plants with flexible branches are easiest.

There are numerous espalier techniques to employ from the very simple and informal designs to complicated formal patterns and even fences. One of the popular patterns is a multiple, horizontal cordon or arms. It consists of a straight trunk and has two or three sets of opposite lateral branches trained in tiers.

Formal espaliers usually need a trellis or some other framework for support. The framework also provides a guide for training branches. Wooden trellises should be constructed of rot-resistant woods or pressure-treated lumber. Use terminal posts with wires stretched taut between them at different levels or tiers.

Some espaliers are trained against a solid wall of either stone or wood without a supporting framework. The plant should be placed six to ten inches away from the wall to allow adequate room for the root growth, air circulation and pest control. Train plants directly to masonry walls with anchoring devices such as masonry staples or screw eyes in the mortared joints. On wood walls screw eyes work best.

To establish and maintain an espalier, prune and tie new shoots to conform to the pattern. Prune all stray branches that grow outward at right angles to the flat surface and those that grow beyond the boundaries of the desired pattern. Use a stretchy plastic plant tie tape to loosely train new shoots to the wire or hardware. To maintain an espalier takes a lot of regular maintenance. During the first several years of establishment, it may require pruning three to four times during the year for proper training, however once established maintain by an annual pruning.

Almost any plant can be espaliered but some are particularly suitable as espaliers. Plants that produce many flexible lateral branches and attractive flowers, fruit, and foliage and/or bark are excellent choices. If you are using an apple tree or other fruit trees be sure to use a dwarfing rootstock. This will help to minimize pruning and also allow early fruiting. For apples use an M-26 or M-27 dwarf rootstock.

The following species are good choices for espalier plants:

  • Acer palmatum — Japanese maple
  • Camellia japonica and C.-sasanqua — camellia
  • Cercis canadensis — Redbud
  • Chaenomeles speciosa — flowering quince
  • Cotoneaster spp. — cotoneaster
  • Forsythia intermedia — forsythia
  • Ilex spp. — holly
  • Lagerstroemia indica — crape myrtle
  • Ligustrum japonicum — privet
  • Magnolia stellata — star magnolia
  • Malus spp. — apple, crabapple
  • Prunus spp. — peach, cherry, plum
  • Pyracantha spp. — firethorn
  • Pyrus spp. — pear
  • Taxus spp. — yew
  • Viburnum spp. — viburnum

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Collier Arbor Care 75th Anniversary Logo

2012 marks our 75th year of tree, shrub and lawn service to the Portland metro area!

Stay up to date on important landscape tips and alerts by signing up for periodic emails. Sign up by April 16 and receive an invitation to our 75th Anniversary and Arbor Day Event!