We have had a bitterly cold winter, but that does not give us a clue whether or not our last frost will occur in March or May. Be prepared to water young seedlings if the rains do not oblige, or to throw some row cover over delicate plants that might not be hardy enough to withstand a late frost.
While the University of California experts do not recommend early planting with cloths or other plant protectors, they do endorse planting early if you pre-warmed your soil, perhaps by laying down plastic sheeting after last month's rains. If your soil measures at least 65°F three inches deep, plants set out now can get a head start, but keep the row cover handy for especially chilly nights.
If you did not start seeds of peppers, eggplant, basil and tomatoes last month, get those started as soon as possible. Seeds for heat-loving vegetables germinate more quickly with bottom heat of 75°F.The warmth helps the plants develop a strong root system. Wait to put stocky seedlings in the ground until the soil is warm, in late April or May.
Pet your plants. Research has shown that gently brushing your tomato and pepper seedlings with your hand causes them to grow shorter, sturdier stems, with shorter spaces between branches. This response may be the plant's way of defending against animals. In any case, it is fun to pet plants.
Some vegetable seeds can go directly in the ground this month, if the soil is not too wet. Radishes, kale, spinach, chard, parsley and peas all grow well in cool spring weather. Cole crops such as broccoli, cauliflower, Brussels sprouts and cabbages can all be planted now, too. Be sure to give larger plants enough space in the garden to reach their full potential.
Seeds for other crops, such as leaf lettuces, spinach, green onions, some peas and beets, can be broadcast in beds. Water after sowing, then wait to water again until your plants have their first true leaves. Too much moisture on tiny sedlings can rob the fragile roots of oxygen and make them succumb to root diseases, such as damping off.
Thin seedlings as needed to allow the others more space. Don't toss these thinnings; they are edible and can give you an extended harvest, beginning with micro-greens and baby vegetables and ending with full-grown heads of lettuce, beets or spinach. When you sow thickly, there is little room for weeds and the abundant plants actually form a micro-climate that can conserve water.
Sow flower seeds in flats or directly in the ground. Marigolds, nicotiana, dusty miller, Shasta daisies, nigella and cosmos can all be started now. Over-wintering perennials appreciate a haircut now to stimulate new growth and help them look pretty after the hard, cold winter.
Plant seed potatoes this month, but not in soil that recently hosted other members of the nightshade family. Nightshades include tomatoes, peppers and eggplant. Any soil-borne disease that affects a nightshade vegetable can survive in the soil and inflict the next nightshade crop, too. Instead, plant potatoes where you formerly grew beans, squash or leafy crops.
If you lost a citrus tree to our early, killing frosts, March or April would be a good time to replace it.
Local nurseries offer so many tubers and bulbs to choose from in March: calla lilies in soft and bold colors; tuberoses with their luscious petals and sensuous fragrance; dinner-plate dahlias and many more.
As shrubs and herbs begin to show new growth, give your plants some nourishment. Read fertilizer and amendment labels carefully first.
Prune spring-flowering shrubs like lilac when they finish blooming and feed them, too. Cut and remove suckers and watersprouts from trees and roses. Water sprouts are the shoots that grow straight up toward the inside of the plant. They promote disease and insect problems by restricting air flow in the center of the plant.
Watch for pests, including slugs, snails and aphids. Wash aphids off with a blast of water, and if you come across some bugs you do not know, bring them into the Master Gardener office for identification (hours below).
Workshop:Napa County Master Gardeners will conduct a workshop on “Warm-Season Veggies” on Saturday, March 15, from 9:30 am to 11:30 am, at the University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Prepare now for your most successful vegetable garden ever. Learn what to plant from seed, how to choose transplants, and when to plant for a bountiful harvest from spring into fall. Online registration (credit card only)
Mail in registration (cash or check only)
Napa County Master Gardeners welcome the public to visit their demonstration garden at Connolly Ranch on Thursdays, from 10:00 a.m. until noon, except the last Thursday of the month. Connolly Ranch is at 3141 Browns Valley Road at Thompson Avenue in Napa. Enter on Thompson Avenue.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. Napa County Master Gardeners ( http://ucanr.org/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.