Every gardener in Napa has been longing to dig in the garden and bask in the warmth of May. Our wet winter left the soil soggy and impossible to work with or walk on. On the other hand, daffodils, tulips and other spring flowers extended their show in the cooler temperatures, although camellia blossoms turned brown in the incessant rain.

What we'd like now is the occasional late-spring shower so that we don't have to start watering yet, and mild temperatures in which to enjoy the roses, iris and wildflowers. But we should plan for the norm, which is sudden heat sometime during the month and drying winds from the north.

Napa County Master Gardeners have planned a free workshop to prepare you for the warmer growing season. "Basics of Spring Vegetable Gardening: Part Two" will be held today at 9:30 a.m. at the University of California Cooperative Extension office in Napa, and will be repeated on May 20, at 9:30 a.m. at Napa Valley College's Upper Valley Campus. For more details, visit the Napa County Master Gardener web site at http://groups.ucanr.org/mgnapa/index.cfm.

This month, the Napa County Master Gardeners' television show on Channel 28 will feature some of the top plants for Napa Valley. Show times are 11 a.m. on Thursdays and 7 p.m. on Saturdays.

Olive Fruit Fly Alert: All homeowners with olive trees should be aware of this devastating pest. It lays eggs just under the skin of the fruit and renders it useless for curing. And unless the damage is limited, it can also render the fruit useless for pressing.

Olive trees are in bloom now. If you don't intend to harvest the fruit, take steps now to prevent fruit formation. Use a strong blast of water to knock off blossoms, or apply a growth regulator, such as Florel or Fruit Stop. Remove any fruit that develops after the growth regulator is applied. Untreated residential olive trees can provide a virtually endless supply of olive flies. The flies are mobile and move easily from landscape trees to commercial groves.

If you want to use your olives for oil or table fruit, contact the Agricultural Commissioner's office at 253-4357 about the use of the bait spray GF-120 Naturalyte. Two other products, Surround WP and Surround at Home, act as a repellant and are available for home and agricultural use. Traps can lower the number of fruit flies and reduce fruit damage. Available traps include the McPhail, yellow panel and OLIPE types. View the "Olive Pests and Diseases" section at http://cesonoma.ucdavis.edu/HORTIC/research_pubs.html for information on the OLIPE trap.

Soil management

* Apply mulch now to suppress weeds, retain moisture and protect the soil and surface roots from the summer sun. Use at least two inches of organic material around shrubs and trees, extending to a foot beyond the drip line and to within six inches of the truck. Wait until the soil is well warmed before using mulches around summer vegetables.

* Check your drip-irrigation system to make sure it's operating properly. Clean filters, check emitters and spray heads, inspect lines for leaks and adjust the automatic controller as the weather gets warmer and drier. Open the end caps and flush out the lines after making repairs.

* Monitor soil moisture, especially if there are dry winds and no late spring rains. Dig three to six inches deep. If the soil is dry and crumbly, it's time to start irrigation. Shrubs and trees have 90 percent of their roots in the top three feet of soil, so irrigate as much soil surface as possible. Use the following rule of thumb: one inch of water applied to the surface will moisten the soil to a depth of one foot. Apply three inches before the heat sets in and repeat every four to six weeks during the summer.

* Smaller shrubs, flower beds and vegetable beds should get a good soaking of one to three inches if the soil is dry.

Planting

* Sow annual flower seeds directly in the soil or set out six-packs. Consider cosmos, dahlias, lobelia, marigolds, nasturtiums, nicotiana, petunia, phlox, salvia, sunflowers, sweet alyssum and zinnias.

* Long-blooming perennials provide a good source of cut flowers. Try alstroemeria, coreopsis, gaillardia, gloriosa daisy, lavender, purple coneflower, scabiosa, Shasta daisy and yarrow.

* Sow these vegetable seeds directly in the soil: beans, carrots, corn, cucumbers, endive, lima beans, lettuce, melons, peas, pumpkins, radish, summer squash, Swiss chard and turnips. Install a support system for climbing plants now as hammering posts in later could damage root systems.

* Plant seedlings of heat-loving eggplant, peppers and tomatoes.

* Fresh-picked herbs add zest to recipes. Good choices to plant now include basil, chives, cilantro, oregano, parsley, rosemary, sage and thyme.

* Plant spring-blooming shrubs like azaleas, rhododendrons and camellias.

* Tender shrubs like bougainvillea, fuchsia, hibiscus, lantana and mandevilla may also be planted now.

Maintenance

* Prune spring-blooming shrubs and vines when they have finished flowering.

* Deadhead (remove dead flowers) from shrubs and other plants so the plant directs its energy to producing new growth rather than seed.

* When the foliage on spring bulbs turns yellow, cut it off, or wait until it turns brown and pull it off. If bulbs are crowded and didn't bloom well, mark them to divide in summer.

* If necessary, thin the fruit on your fruit trees so that the remaining fruit can develop to a good size. Gently twist fruit off when it is 1/2- to 3/4-inch in diameter, leaving about six inches between each fruit. Excess fruit can also break branches.

* Watch for aphids, earwigs, snails and slugs.

* Keep weeds in check by pulling seedlings now, when they are more easily removed. Don't let weeds go to seed.

Harvest

* Enjoy the vegetables from your winter planting: bok choy, cabbage, chard, cauliflower, fava beans, green onions, lettuce, parsley, peas, radishes and beets.

Napa County Master Gardeners answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to noon, at the UC Cooperative Extension office, 1710 Soscol Ave., Suite 4, Napa, 253-4221, or toll-free at 877-279-3065.