As spring arrives in Napa County, local gardeners are preparing to plant cool-season vegetables that thrive in the region’s mild temperatures. According to Pat Hitchcock, a UC Master Gardener of Napa County, March is an ideal time for starting crops that do well in cooler weather and can be harvested before summer heat sets in.
Napa’s average temperatures in March range from 40°F to 60°F, rising gradually through May. These conditions are suitable for many annual vegetables that mature quickly. Gardeners can expect to harvest fresh produce such as radishes, carrots, turnips, peas, lettuce, and leafy greens within two to three months. This schedule allows space for warm-season crops like tomatoes later in the year.
Root vegetables should generally be started from seed directly in the ground since their seedlings do not transplant well. Beets are an exception. Radishes mature quickly—classic red varieties can be ready in about a month—and successive planting every few weeks ensures continued harvests until it is time for summer crops.
Peas also perform well when planted now. Vining types save space if grown on trellises or towers. Both snap and snow peas are productive at this time of year; English peas also grow well but require shelling.
Lettuce and other greens benefit from cool spring weather and can be harvested within a couple of months. Asian greens such as baby bok choy and mustards are recommended options. Arugula tends to be milder when grown in cooler temperatures. Cilantro grows rapidly but may need replanting as it goes to seed quickly.
Spinach, beets, and chard take longer to mature but will grow faster if seedlings are used instead of seeds. Seedlings of broccoli, cauliflower, cabbages, kale, and kohlrabi can also be set out now.
Garden centers currently offer many cool-season vegetable seedlings but Hitchcock advises against purchasing warm-season vegetables like tomatoes or peppers until soil temperatures rise consistently above 50°F at night—typically not until late April or May.
Spring vegetable growers should watch for common pests such as snails and slugs which thrive in moist conditions. “According to UC IPM (Integrated Pest Management) the first line of defense is hand picking and trapping to reduce their numbers,” Hitchcock notes. She recommends baits with iron phosphate as the active ingredient because they are considered safe for animals and organic gardens; baits containing metaldehyde should be avoided due to toxicity concerns.
Aphids often target tender new growth; regular inspection and spraying with water can help control infestations. Birds may damage emerging seedlings so barriers such as row covers or netting are advised.
The imported cabbageworm—a larva of a small white butterfly—can affect brassica family plants like broccoli or kale by laying eggs on leaf undersides. Checking leaves regularly or using physical barriers like row covers helps prevent problems with less effort.
For more information about pest management resources, gardeners are encouraged to consult the UC IPM site.
Hitchcock adds: “If you really must think about tomatoes, early March is a good time to start your favorite varieties indoors.” Seedlings started now will be ready for outdoor planting after harvesting spring vegetables.
UC Master Gardeners of Napa County will host workshops on “Spring and Summer Vegetables” on March 14 at UC Cooperative Extension in Napa and on March 15 at Yountville Community Center. The sessions will cover topics including soil preparation, irrigation, seed starting, transplants and common problems faced by gardeners.
A separate workshop titled “How to Plan Planting a Vineyard” will take place on March 28 covering site evaluation and land preparation strategies for new vineyards.
The Master Gardener Help Desk offers support through an online form or via email for those seeking advice on gardening issues; walk-in assistance is available Mondays and Fridays at the University of California Cooperative Extension Office in Napa.
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