IN THE GARDEN LATE RAIN LEAVES VALLEY AWASH IN BLOOMS.

Byline: JOSHUA SISKIN

`April showers bring May flowers'' are words whose truth has been amply illustrated this year. Our late rain has brought an abundance of blooms and a massive wave of first roses in May, an annual show that typically takes place, in the Valley, sometime in April.

Phenology is the science that addresses the relationship between periodic biological phenomena -- such as the migration of birds or the flowering of plants -- and weather patterns. For example, it is generally acknowledged that lilacs bloom when the danger of winter frost is over and that jacaranda trees flower immediately prior to the onset of hot weather. Hang around plants long enough, study them closely in relation to meteorological changes, and you will be able to predict the weather as well as anyone.

As a rule, soon after your flowering plants look their best is when you should prune them; that is, if you want them to bloom again soon. If you wait until all the flowers on your Euryops daisy shrub have faded, you will have to bide your time until late summer to see another flush of blooms.

With petunias, just when they are so full of flowers that you cannot see their leaves, cut them back by a third and prepare for another petunia wave. Wait another two weeks to prune them, after they start to get leggy, and you may not see a single flower return. Cutting back by one third at the moment of fullest beauty is also a wise practice to follow in the case of impatiens and bedding begonias, if you wish to see them bloom again in a matter of weeks.

Never be afraid to prune as long as you are careful and do not remove more than a third of a plant's growth at one time. Some rapid growers, such as the many species of Salvia (sages), will respond well to a more vigorous pruning, where one-half to two-thirds of the growth is removed. If you have the time, it is best to prune out individual shoots or branches selectively, rather than head back wholesale. Most ornamental grasses, on the other hand, may be cut back to ground level without a second thought.

Over the years, I have found Justicias to be one of the most satisfying groups of plants. If you want a 3-foot shrub that blooms nearly all the time with very little water and may be grown in almost any situation, from individually in pots to collectively in a hedge, select the shrimp plant (Justicia brandegeana) with its distinctive prawn-shape bronzish bracts.

Other nonstop blooming Justicias include the pink Justicia carnea, the orange Justicia spicigera, the silver Justicia betonia, and golden Justicia aurea, and the yellow and pink Justicia `Fruit Salad.'

A gnawing problem that seems to be getting worse is oleander leaf scorch. It is not a good idea to plant oleanders at this time since there is a good chance that the plants will soon become infected with this bacterial disease, which is carried by the glassy winged sharpshooter, a sucking insect whose wings are folded tentlike on its back.

What is most frustrating about this disease is that the plants do not die right away, but may linger for several years. Oleander leaf scorch is easy to diagnose since oleanders are normally the picture of health. Any fading or thinning of leaves, even prior to signs of burnt foliage, is sufficient evidence that the plants are infected.

You can leave them alone and watch as they go into futher decline, or remove them right away. You can be sure of only one thing: Oleanders, once infected with this disease, will not recover.

TIP OF THE WEEK: Once upon a time, coleus and impatiens were shade garden standbys, but not anymore. For several years, large-leafed sun coleus has been available and now, only this spring, a new interspecific impatiens hybrid call `SunPatiens,' that grows in full sun, has been introduced. It is a cross between New Guinea impatiens and a wild impatiens species. Although promoted as full-sun plants, you should probably grow them in half-day sun since Valley heat can be brutal even for sun lovers. Roses, for example, certainly need a plentiful supply of light yet, in the Valley, they do best when receiving no more than half a day's worth of direct sun.