GARDENING : ARRIVAL OF SUMMER NEEDN'T MEAN HALT IN PLANTING.

Byline: Joshua Siskin

You can tell summer has arrived in Los Angeles when the jacarandas are enshrouded in a violet tunic, when the star jasmine is studded with fragrant white pinwheels, and when the date palms on Ventura Boulevard across the street from Sav-On in Sherman Oaks are loaded with sticky orange fruit.

Just as spring arrives in February in our fair city, it is only fitting and proper that summer should come in May.

Planting may be done throughout the summer as long as attention is focused on proper soil preparation, mulching and watering. The spading fork is your most valuable ally in this process, because loosening and aerating the soil will assure rapid root growth, the most crucial factor in the establishment of any plant. Use lots of organic amendments or compost - as much as your back can stand - to improve the soil structure.

After planting, spread a thin layer of peat moss or redwood compost on the soil surface. These highly absorbent materials will slow the evaporation of water from the ground and keep roots cool and carefree in the hottest weather. Be sure to keep the mulch away from your plant's crown (where its main stem or trunk meets its roots), to avoid fungus problems. Another highly effective mulch is pea gravel.

It is important, all the same, not to mulch too heavily. When more than 2 inches of mulch is used, the upper soil stays so moist that roots never have to bother to grow very far below the surface. The result is plants that become quite wobbly, like so many loose teeth, with insubstantial roots and arrested development overall.

Yvonne Savio, of the Common Ground Garden Program, which is sponsored by the Los Angeles County Cooperative Extension of the University of California, has compiled a list of garden tasks for the month of May. This list was developed by UC researchers and master gardeners trained by Cooperative Extension. Some of Savio's recommendations are included in the gardening guide that follows.

Summer gardening guide

Citrus trees are best planted in warm weather. Keep them mulched with rough, uncomposted materials such as straw, pulled weeds or fresh garden trimmings.

Paint trunks of fruit trees with white latex paint diluted to half paint and half water. The paint will reflect summer sun that might otherwise cause trunk cracking and cavernous canker formation.

On peach, nectarine, apple, plum and apricot trees, thin fruit so that it will size properly. Along the branch, there should be 5 to 8 inches between individual peaches, nectarines or apples and 4 inches between plums or apricots.

Do not use diseased leaves for compost or mulch, a practice which may cause the pathogenic agent - usually a fungus - to proliferate in your orchard.

Use trellises for vines, squashes and other crops whenever possible. Keeping fruit from making contact with the ground will prevent fruit rot, keep moisture-seeking critters such as sow bugs and earwigs off your produce, and discourage snails and slugs as well.

To increase pollination that results in greater production of most crops, you must attract bees. You can do this by planting ornamentals with blue or mauve flowers, such as borage, rosemary, garden sage, mint and trailing lantana.

If you planted asparagus this spring, refrain from harvesting it, since the plant should direct all its energy into building a strong root system. When you harvest shoots, you encourage the growth of other shoots, which will siphon off energy that would otherwise go to the roots.

To keep ants away from your hummingbird feeder, spread olive oil on the tip that dispenses the sweet water. This will deter the ants without discouraging the birds.

Tip of the week: For answers to any of your gardening questions, call the Master Gardener Hotline at [phone]. The Common Ground Garden Program helps Los Angeles County residents garden, compost and preserve their harvests. It also helps people in low-income areas start community and school gardens. For information about the Master Gardener course and to learn about volunteer opportunities starting and maintaining gardens, call [phone].