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Growing Concerns: Urbanization stresses Madrona trees
The Pacific madrona is in trouble, and much of the blame is ours. Known for its vivid, orangey bark and smooth, sinuous limbs, the Northwest native tree is beset by a variety of problems, the most serious of which is brought about by human interference.
A broad-leafed evergreen tree distantly related to the rhododendron, Arbutus menziesii ranges the coast from southern British Columbia to northern California. Also known as madrone or arbutus, its often seen in its shrubby form, but can grow from 50 to more than 100 feet tall. It prefers a mild, coastal climate and well-draining, acidic, rocky soil, as well as the typically dry summers of our region. Madrona doesnt like being shaded by other trees, and often grows on the perimeters of Douglas fir forests and along rocky cliffs.
It normally blooms in May, but this years early spring has many madronas blossoming right now. The flowers evolve into orangey-red berries, set among long, leathery, evergreen leaves that usually fall in July and are replaced by new, paler green leaves.
This magnificent tree is important to man and beast. Its hard wood has little commercial value, since it doesnt season well and tends to warp and crack. However, the madronas deep root system is without peer in stabilizing bluffs. Drive Coupevilles Madrona Way and youll see them at work. The tree is also important to wildlife. Bees, butterflies and hummingbirds are drawn to its fragrant panicles of white flowers. Deer browse the lower blossoms. Birds eat the berries. Chipmunks, squirrels and birds find homes among its sleek branches.
In its natural setting, the madrona is at the mercy of a wide variety of fungi and leaf-chewing insects, as well as damage from cold winter winds. Fungal leaf spotting is particularly intense during wet winters and springs. And while dry summers are necessary to its existence, prolonged periods of drought can lower the trees resistance to disease.
One fungus in particular, Nattrassia mangiferae, causes a canker, which often produces gnarled callouses on affected trees. According to a University of Washington study, these cankers are most often seen on trees growing along the shoreline, and are especially aggressive among stressed trees.
As the Pacific Northwest becomes more urbanized, the health of the Pacific madrona is on the decline. Ongoing data collection by the Canadian Forest Service in British Columbia shows that stress caused by human activity is a far more serious problem than what nature visits on the madrona. The chief causes of man-made stress are construction, paving over roots, and installing sewage drains. Madronas on developed property often suffer from herbicide application. In urban areas, the tree is sensitive to air pollution. Irrigation can cause root rot. Another fungus causes limb dieback and formation of smooth, black cankers that destroy the trees cambium layer (the living, growing cellular layer beneath the bark).
So far, there are no effective commercial means of alleviating the madronas multiple miseries. University research is ongoing in both the United States and Canada, however, to find ways to save this majestic tree.
In Port Angeles, one man took up the cause to save a failing, centuries-old madrona and won. The tree, located on a city lot in a commercial area, is 85 feet tall, with a crown spread of 95 feet and a trunk circumference of 21 feet, five inches.
Arborist James Causton began his campaign to save the ancient tree in 1990. He solicited donations to purchase the lot on which it grew. While awareness of the tree was raised, sufficient funds were not.
But Causton never gave up.
Nine years later, a local woman purchased the lot, planning to turn it into a park to memorialize her late husband. Causton pleaded his cause to her, and she accepted his plan to restore the madrona to health.
Since that time, Causton and a dedicated corps of volunteers have removed 40 cubic yards of inappropriate mulch and replaced it with a combination of organic, composted horse manure and wood chips. The soil on the entire site was inoculated with beneficial mycorrhizal fungi and topped with a four-inch layer of Douglas fir wood chip mulch. The most recent improvement was removing and rerouting a sidewalk that had been within 18 inches of the trunk.
The formerly ailing tree is now, Causton claims, the largest healthy madrona in the state of Washington. For his efforts, Causton was honored by the International Society of Arboriculture, Pacific Northwest Chapter, and the Washington State Arbor Day Council.
As for the madrona, it will likely see a few more centuries.
To help preserve madronas on your property, avoid disturbing the roots and dont water around them. Trees past five years of age should not receive any artificial irrigation.
If you want to grow your own madrona, its best to purchase from a nursery that specializes in native plants. The chances of a wild transplant surviving are risky, due to the trees long, sensitive taproots. Bear in mind that a seedling madrona is much easier to establish than a mature plant. Give it a fighting chance by siting in a dry, sunny, well-draining spot where irrigation and foot traffic is minimal. Do not fertilize.
Madrona isnt suitable for all gardens. Its messy, with year-round litter of peeling bark, falling flowers, leaves and berries. Few plants can survive beneath it. Natives such as salal, Oregon grape and snowberry are your best bets. If grown too close to lawn or cultivated plants, a madrona will likely get far more water and fertilizer than it can stand. Paths and heavy activity beneath and around the tree can cause soil compaction that once again, negatively affects those sensitive roots.
The best way to care for a madrona may be to treat it with benign neglect. Tread softly and allow it to be the wild and beautiful tree it was meant to be.
Mariana Graham writes this biweekly column as a volunteer WSUIsland County Master Gardener. Contact her at firstname.lastname@example.org.