St. Patrick's Day has come and gone and some gardeners have been in the garden planting cool-season vegetables. What are cool-season vegetables? They germinate in cool soils and make their best growth at temperatures from 40 to 70 degrees. These vegetables can be planted as soon as the soil can be tilled.

Check garden soils by taking a handful of soil and forming it into a ball. Squeeze the ball tightly and toss it into the air. If it crumbles, you have the signal to plant. If the ball keeps its shape, delay working the soil until it dries out.Perennial vegetables are not common, but two, asparagus and rhubarb, can be planted right now. Improved varieties of asparagus include Mary Washington, Waltham Washington or Jersey Giant. Asparagus is normally grown from plants or crowns. Dig a trench 8 to 12 inches deep and plant the crowns in the base of the trench. As the new sprouts emerge, add additional soil until the trench is even with ground level. This develops an extensive crown that is well protected from frost or other problems.

Rhubarb can also be planted right now. Canada Red, Ruby, and Valentine are improved varieties. Give these plants plenty of room as they spread three feet or more. Remember rhubarb leaves are poisonous so don't use them as an ornamental next to play areas.

Other cool-season vegetables include the cole crops. Cabbage, broccoli and kohlrabi are excellent for planting right now. Cole crops require cool temperatures and high fertility. There are several varieties of broccoli that do well under Utah conditions. Packman, Green Comet, Premium Crop and Paragon are all superior hybrids.

Excellent varieties of cabbage include Savoy Ace, Ruby Perfection, Market Prize, Stone Head and many others. Kohlrabi makes an excellent substitute for turnips with Winner hybrid as the preferred variety. Turnips are very susceptible to the root maggot, and I'd strongly recommend you try kohlrabi instead. All cole crops need to be planted early and fertilized with sufficient nitrogen fertilizer. Insufficient fertilizer and hot temperatures produce tough, bitter crops.

Plant onions right now. Some of the finest onions in the world are produced just north of Salt Lake City. It's amazing how many gardeners complain they don't get good onions. Giant, softball-size onions come from seed, not from sets. Onions are sensitive to day length, and some gardeners learn too late that they selected the wrong variety. Utah Yellow Sweet Spanish is an old standby but still an excellent variety. Other varieties include Early Ebenezer or Walla Walla. Onion sets are best used for green onions or small early onions. Onions germinate at very low soil temperatures, so plant them soon.

Peas are an excellent choice for gardens. If you like snap peas, choose Sugar Ann, Early Snap or Sugar Daddy. Edible podded peas for stir-fry include Little Sweetie, Snow Flake and Oregon Sugar Pod. Other peas include Lincoln, Early Frosty and Patriot.

Radishes grow as quickly as any garden vegetable I know. Many are ready to harvest within four weeks of sowing. Plant continuous crops every week or two to ensure continuous harvest. Radishes come in all colors. In fact, Easter Egg Radish produces pink, lavender, red and white radishes out of the same packet. Radishes need plenty of fertilizer and moisture to avoid hot radishes or pithy hollow interiors.

Finally, spinach isn't just for Popeye. Good hybrid spinach varieties include Melody, and Skookum. These varieties have a short growing season, mild flavor and are very productive. Again they should be planted in the early spring to develop the best flavor.

If you have trouble locating any of these varieties, check with your local nursery. Many local nurseries stock varieties that do well in Utah. If you can't find them locally, send 10 cents plus a self-addressed, stamped envelope to: USU Extension Service, 2001 S. State, Room S1200, Salt Lake City, UT 84190-3350 for a source sheet of selected vegetable varieties.

Continue planting most cool-season vegetables until May 1. Then delay planting them again until midsummer. Vegetables planted for a fall harvest produce excellent quality vegetables. Enjoy these cool-season vegetables then utilize the growing area for other produce during the season.

Spring 1991 Garden Workshops offered by USU Extension are open to the public at no charge.

- March 26, Tuesday, Trees and Shrubs: Care and pruning of shade trees and shrubs.

- April 2, Tuesday, Lawn Care: Water, fertilizing, mowing and maintaining a green lawn.

Granger Bishop's Storehouse, 3548 S. 7200 West, upstairs meeting room. March 28, Thursday, 7-8:45 p.m. Fruit in the home garden: proper care and planting, pest control and pruning of fruit trees.