IN THE GARDEN SPLIT BARK A COMMON WOE.

Byline: JOSHUA SISKIN

Q: I have been in the same house for 28 years. I have a large orange tree with the best-tasting naval oranges which was full grown when I moved in. Lately, I have noticed the bark on a couple of branches is splitting open and coming off. What can I do for this problem and what is causing it? My neighbor, by the way, has the same problem with her apple tree.

- Sally Castiglia, Van Nuys

A: Split bark is common on the branches of thin-barked trees and nearly all fruit trees have thin bark. Split bark is usually the result of temperature extremes. Scalded and split bark can be the result of either a freeze or a spell of very hot weather. Thus, the super abundance of burning hot days this summer would explain the split bark on your, and on your neighbor's, trees.

Split bark, in and of itself, is not a hazardous condition. The worry is that insect pests and disease organisms may take advantage of the situation and cause serious problems by nesting in or infecting the tree under the cracked bark.

You can prevent potential problems by taking a sharp knife and tracing a line that goes about one inch all around the outside edges of the split bark. Remove the bark to this line. After each slice of the bark, dip your knife in a 10 percent bleach or 70 percent rubbing alcohol solution; this procedure will probably knock out any infections that may have begun under the bark. After peeling off the split bark, leave the area exposed and it will callus over. Do not cover with pruning tar as this will interfere with the callusing process. To prevent bark splitting in hot weather, make sure trees are well-watered.

Q: I live in Lancaster and am clearing an area in which I plan to plant tulips. But, I have several questions. I know they are planted in the fall but when? September, October or November? When do I water them? We may get a couple of rains between fall and spring or none at all.

I have never planted bulbs before because they are so short-lived and it is hard to have flowers here because of the rabbits and other wild small creatures.

- Maida Cunningham, Lancaster

A: First, you must protect your tulip area from those pesky rabbits and there is no way of doing this effectively other than by putting up a fence several feet tall. Such fences, sold by the foot, can be acquired inexpensively enough at home improvement centers. To keep out ground squirrels, you will have to cover your emerging tulips with chicken wire. Gopher prevention means creating an underground chicken wire barrier, at least three feet deep. Soil for tulips should be well-drained. Amend it to the proper planting depth - three times the girth of your bulbs - with compost. Water when planting and then regularly after shoots appear.

Once you have your soil amended, and your planting area fenced and wired, you will want to consider what kinds of tulips to plant. Be aware that the fanciest tulips, which are usually hybrids from Holland, are also the most problematic, needing lots of cold in the winter to bloom in the spring.

Even when getting their allotment of cold, they generally do not come back for more than two springs. Botanical or species tulips, on the other hand, although not as gaudy as the hybrids, bloom reliably even when winters are warm, and may persist in the garden for many years.

In the San Fernando Valley, it is recommended that we refrigerate tulip bulbs for six weeks, to mimic the cold winter they prefer, prior to planting.

To ensure strong bulbs from one year to the next, do the following: Three weeks after tulips bloom, clip off their faded flowers. Flower petals that fall back into the leaves cause the leaves to rot before they have finished making food for next year's bulbs. Cutting off the flowers also deprives them of the ability to make seeds, an energy-intensive process that will also take away food from next year's bulbs.