Willow Glen Resident

Gardening

Fall Fest: The fast-growing, deep-rooted red oak is native to the eastern U.S. but grows well in Northern California. Its pointed, lobed leaves look somewhat similar to a maple from afar and turn orange or reddish-brown in fall.

If a tree falls on a street, it will make a sound and a roadblock

By Tony Tomeo

There was no wind. There was no rain. A large fir tree fell across East Zayante Road simply because I happened to be in a hurry. Trees seem to have made a tradition of blocking roads when most inconvenient. A few neighbors and I decided to wait there while the road was cleared instead of wasting even more time by driving an alternate route.

While waiting and sometimes pacing, I saw several other potentially hazardous trees that I never noticed before. Other firs, alders, maples and even oaks were leaning precariously, directly above the road where they cannot be seen from inside a non-convertible car. If this winter is as rainy as predicted, the road will probably be blocked a few more times by fallen trees.

Unfortunately, trees fall onto more than just isolated roads. Any seemingly innocent tree in the best-maintained gardens can fall onto other garden features, homes, cars, the neighbor's cat or anything that happens to be in the way. Only a minor percentage of trees fall, but when they do they can cause serious damage. The neighbor's cat would probably get out of the way, but homes, even mobile homes, are not so speedy.

Big mature trees that can cause the most damage are typically more likely to fall than smaller, relatively harmless trees. Because they are too large to be sheltered by smaller trees, big trees are more exposed to destabilizing wind. Their larger canopies have more wind resistance, which exerts more leverage against their supportive root systems. Mature trees are also more likely to have destabilizing root problems, particularly if in regularly irrigated areas. Excessive moisture promotes both shallow rooting and root decay.

As if this is not enough to worry about, trees can also drop limbs. Among the largest trees, limbs can be as large as small trees. Those that fall from higher up come down with more inertia and can land considerably farther away than lower limbs. One just might surprise the neighbor's cat.

Falling trees and limbs become more problematic as weather becomes windy and rainy. Wind is, of course, what blows the trees and limbs down. Rain softens the ground so that it is more difficult for roots to hold on, and can also add weight to foliage. Deciduous trees eventually have the advantage of dropping their leaves for the winter, losing the weight and wind resistance that might otherwise be their demise. However, evergreen trees are always vulnerable to the weather.

While the weather is still relatively calm, potentially hazardous trees can be pruned to be considerably safer through winter. Heavy or dense canopies can be thinned to decrease leverage exerted on the limbs by the weight and wind resistance of the foliage. Thinning also alleviates some of the burden on trees that seem to lack stability.

Certain structural deficiencies can be accommodated or even corrected by standard pruning procedures. If necessary, dangerously hazardous trees that cannot be repaired should be removed.

Arborists are horticulturists of trees, or "tree physicians." It is impossible to predict every tree problem, but arborists can identify most potential hazards and prescribe corrective procedures. Even if certain trees need nothing at all, it is good to hear it from an arborist. A list of certified arborists can be found at the website of the International Society of Arboriculture at www.isaarbor.com.

Tree of the Week: red oak

Red oak, Quercus rubra, is the oak that thinks it is a maple. Like the red maple, red oak initially produces red new leaves in spring. It grows about as fast and large as a silver maple, and produces a similar not- too-dark shade, but has better structural integrity and more complaisant roots. The 5-inch-wide by 7-inch-long leaves have pointed lobes like those of sugar maple leaves, and even turn similar, although subdued, shades of reddish brown or orange before falling in autumn.

Upon closer examination, however, oak leaves have pinnate instead of palmate venation, and are not arranged in pairs like maple leaves are. ("Pinnate" oak leaves have single prominent midribs. "Palmate" maple leaves have multiple prominent midribs that radiate from the petioles, leaf stalks).

Listen to Tony Tomeo's 'New Image Garden Report' Friday mornings at 8:10 a.m. on KSCO-1080 AM (or online at www.ksco.com). He can be reached at www.ttomeo@newimagelandscape.com or 408.358.2574.