COLORS OF SPRING ARE UPON US.

Byline: Joshua Siskin

Throughout the East and the Midwest, the brilliant yellow flowers of Forsythia are the horticultural harbingers of spring. In the Valley, the fluorescent yellow flowers of primrose jasmine (Jasminum mesnyi) serve a similar function.

Along the 405 freeway between North Hills and Granada Hills you can see primrose jasmine blooming now. How odd yet wonderful that this plant should have been chosen for freeway planting. Odd because it is deciduous - and deciduous shrubs, whether native or imported, are virtually unheard of in our part of the world - and wonderful because it allows the gardener's eye an opportunity to see a plant that it might not otherwise see.

You will go up and down the streets of the Valley looking for primrose jasmine in vain. This is a shame because the plant is well-suited to a wide variety of horticultural applications. The natural habit of its stems is to arch, which means that primrose jasmine is easily trained over an arbor or up a trellis. It can also be planted along the top of a retaining wall where its tendency toward top-heaviness will cause its stems to bend down, providing you with a flowery wall hanging each spring.

Wherever you would plant bougainvillea, you can plant primrose jasmine. Not only will both plants cover fences and walls with equal alacrity. Both are highly resistant to drought. A major difference between them is that primrose jasmine is more cold tolerant than bougainvillea.

This jasmine is called ``primrose'' because it is one of the first (as in primo) plants of the year to bloom and because its flowers bear a cursory resemblance to roses. In fact, the flowers might remind you more of popcorn than of roses, as they appear almost spherical with irregular edges. If you do not find primrose jasmine at the nursery, you should be able to special order it since, although somewhat exotic, it is grown commercially.

Pink jasmine (Jasminum polyanthum) is far more common. It also blooms at this time of year and is desirable both for its flowers and its fragrance. The flowers are tinged with pink in the bud stage and white once fully opened. Their fragrance is strong, but you have to practically stick your nose into the flower in order to appreciate the scent.

If you want flowers that smell from a distance, plant orange trees. Long lists of plants with fragrant flowers typically omit orange blossoms. No fruit tree is more suited to the Valley than the Valencia orange tree and no fragrance will encompass your entire yard like that of the blossoms or flowers of orange trees, which are also opening now.

Speaking of citrus, Valley gardeners should become more familiar with the kumquat, an outstanding container plant that is full of fruit this time of year. The kumquat tree is the ideal plant for a sunny entry. It can be planted in the ground, where it will probably not grow more than 8 or 10 feet tall or in a pot, where it can be kept at a manageable height by root pruning.

Root pruning of container plants is a practice that is best done in early spring, just before new growth begins. Prime candidates are ficus trees, which will easily become root bound and defoliate, after reaching a height of around 6 feet, if they are not root pruned every year or so. Slower-growing trees, just as with kumquats and ornamental plum trees, should be root pruned every other year.

To root prune any plant, remove it from its container and take or cut away one third of the volume of the soil/root ball. The outer roots can be cut away either with a knife or the sharp edge of a good shovel. Refill the container with fresh topsoil, available at any nursery for a little more than $1 per cubic-foot bag.

TIP OF THE WEEK: To keep cats out of your flower beds, take dried stems of roses or bougainvillea and stand them up in the beds, the bottom few inches of the stems inserted into the soil. Cats will stay clear of the flowers, instinctively keeping their distance from the thorny stems.