GARDENING : COMPARED TO L.A., N.Y.C. IS A LATE BLOOMER.

Byline: Joshua Siskin

I was in New York City last weekend and finally understood why the denizens of that metropolis are in the habit of disparaging those of us who choose to live in Los Angeles. They're simply jealous of our weather.

Spring, for example, arrives approximately two months later in the Big Apple than it does in the Big Orange.

Virtually all of the trees in New York are still leafless. I spotted ornamental pears, Lombardy poplars, saucer magnolias, corkscrew willows and European birches, all of which grow in the Valley and have been in leaf since February. The reason these deciduous trees leaf out earlier in our city is due to the warm weather we typically experience in late winter.

There is one tree, though, that is just now leafing out in both New York and Los Angeles. It is the ginkgo. This tree would appear to open its leaf buds in response to day length rather than in response to temperature. Every year, no matter what the weather, the ginkgo leafs out during the middle of April. This is not surprising once the ginkgo's past has been investigated.

The ginkgo - known as the maidenhair tree because of its fan-shaped leaves, which resemble those of the the maidenhair fern - was one of the first trees on Earth. Its fossils have been found in Europe, Asia, Australia and America. It grows in both tropical and temperate (cold winter) climates, though its origin is tropical. A plant of such wide and ancient distribution apparently had its seasonal behavior fixed when the world's climate - at least where flora thrived - was more or less uniform throughout the year.

New York has developed one tree landscaping technique that every city would be wise to emulate. On selected street corners and broadened parkway strips, the city has seen to it that tens of trees of a single type are planted together, producing a woodsy effect. I saw no less than 30 saucer magnolias planted together and, in another location, over 50 corkscrew willows growing en masse. The kind of relief such plantings give to passers-by is lifesaving. Even if you just ride past such groupings of trees in a bus or taxi, you feel that the city is suddenly not so oppressive, that basic human yearnings have a place there, that the city has a face.

One shrub that's blooming its head off in New York right now is the forsythia. Back East, the forsythia is as famous for its yellow spring blooms as the lilac is for its lavender and mauve ones. The forsythia will flower in colder Valley climates, such as Woodland Hills and in the Antelope Valley. The only problem is that its flowers are a disappointment after having seen some of our own winter and spring bloomers. The vivid golds and yellows on such plants as Acacia Bailyeana, Tabebuia chrysotricha and Dendromecon rigida make the forsythia seem dull and uninteresting by comparison.

August Chadwich of Woodland Hills writes with the following question: ``Does watering indoor plants from above with a watering can (as opposed to soaking water up from below), contribute to the ends of the plants' leaf blades turning brown and drying up?''

The only indoor plant I know of that is adversely affected by having water touch its leaves is the African violet. When African violet plants are watered from above, they turn brown wherever their leaves make contact with water droplets. For this reason, place African violet pots in buckets with a few inches of water and allow pots to soak up water through soil. Ideally, all indoor plants would be watered in the manner of the African violet because such a soaking is the only way to ensure that soil and roots are wetted in a uniform manner.

When just the tips of indoor plant leaves are brown, it's the result of fertilization imbalance or excess or dry air. Potted plants should be fertilized with each watering at one-quarter to one-half the dosage indicated on the fertilizer label. In addition, the pot should be leached (watered copiously) every few months to drain out pockets of accumulated fertilizer salts, which can cause burnt leaf tips.

Tip of the week: For increased flowering of snapdragons, cut blooming shoots when only half their flower buds have opened. Take these severed shoots and use them in vase arrangements, where they can continue blooming for up to a week.