IN THE GARDEN ORNAMENTAL PEAR TREE REACHES A RIPE OLD AGE.

Byline: JOSHUA SISKIN

Q: I have an ornamental pear tree over 25 years old that is not doing well. About a year ago, when it was dormant, I had it trimmed, but the following spring there was very little growth. I have three more trees of the same type that are doing fine. I have treated it for fungus, removed lawn grass from around its base, and fixed my sprinklers so water does not hit the trunk. I have fertilized with various products and put holes in the soil so fertilizer would more easily reach the roots. But this year, again, I have seen very little growth except for some crinkly leaves with brown tips. Is my tree a goner? Please advise because I am thinking of removing it.

- Rich Hollow, Chatsworth

A: Ornamental pear trees are similar to other small- to medium-size landscape trees in one notable respect: They tend to be short-lived.

They have weak immune systems and are visited by a variety of debilitating fungal, bacterial and insect pests. Yes, they require less maintenance than large trees, but are likely to be dead in 20 to 25 years.

What other trees are included in the short-lived list? Purple leaf plum, silk tree (Albizzia julibrissin), bottle brush (Callistemon citrinus) and white birch (Betula pendula). Even crepe myrtles, which may persist for several decades or more, begin to lose their luster, in our environment, after a quarter century, more or less.

You mention that you have several ornamental pear trees and only one appears to be dying. This is not unusual. A group of ornamental pear or other short-lived trees that were planted about the same time will frequently die off one by one within a few years of each other. Do not be surprised if one or more of the remaining healthy trees meets its demise within the next few years.

Ornamental pears are famous for developing scorched foliage as a result of fireblight, a bacterial disease. Fireblight enters the tree by way of the flower petal nectaries and is spread by pruning shears. Remove any burnt shoots or foliage two inches beyond the scorched area and disinfect your shears between cuts by dipping them into a 10 percent bleach solution. Prevent fireblight by application of an antibiotic spray before and after flower buds open.

There is an increasing prejudice against large trees, yet these lend unique atmosphere and value to any living space. One of the complaints against large trees is that they ``take forever'' to reach maturity. Yet, they grow quickly enough, even as they impart a priceless sense of security and permanence to the surroundings.

Large trees, and trees in general, are often dismissed for being ``messy.'' It is true that a giant live oak, for example, may shed its leaves over a period of several months, but this is really more of a blessing than a curse. Oak leaves, like the fallen foliage of most trees, can immediately be put to use as a wonderful mulch. In addition to conserving soil moisture and enhancing soil fertility, a layer of decomposing leaves, distributed over the ground throughout the landscape, will tend to deter snails and discourage lethal soil-borne fungi such as Phytophthora.

How is it that forest trees are verdant and vibrant with no one to care for them? The answer, of course, is that they are fertilized by their very own leaf litter. Ideally, under the influence of leaf mulch, the ground around trees and shrubs will resemble a forest floor, reducing applications of fertilizer and water.

TIP OF THE WEEK: A real problem with large trees is their roots' invasion of water and sewer lines and their cracking and lifting up of sidewalks, driveways and other paved surfaces. For this reason, root barriers are recommended when planting. A root barrier consists of modular panels that are snapped together and placed around root balls or along the edges of sidewalks or driveways, to a depth of 3 or 4 feet, forcing tree roots to grow down into the earth where they cannot cause damage to pipes or hardscape features.