Waiting until after the last spring frost occurs to plant a vegetable garden is by no means mandatory. In fact, cool-season crops, particularly vegetables grown for their tasty roots and leaves, are best planted early before excessively hot summer days arrive that will stunt their growth. Master gardeners encourage spring vegetable planting to lengthen the harvest season and offer more variety to meals.
Choose a garden area that receives full sun. Work into the soil rotted organic matter such as compost, manure or rotted leaves to provide adequate nutrients for plants.
Start planting the hardiest seeds and transplants, such as onions, peas and radishes, 2 to 4 weeks before the frost date as soon as the soil is workable but not sopping wet. Plant semi-hardy vegetables, such as carrots and parsnips, up to two weeks before the last frost date. Keep in mind that semi-hardy vegetables grow best when minimum temperatures stay above 40 degrees Fahrenheit.
Plant spring vegetable seeds at a depth that equals about three times the seed length. Plant lettuce seeds shallowly because they require light for germination. Keep seeds moderately moist as they are germinating.
Plant fast-growing crops, like radishes, amidst slower-growing crops to maximize the garden space. Make multiple plantings of fast-growing crops to extend their harvest season. Harden transplants before they are planted into the ground by exposing them to temperatures about 10 degrees Fahrenheit lower than they have been growing in for about 10 days.
Install a trellis for sugar snap peas to climb up. Cut potato seed pieces several days before planting to prevent rot. Protect emerging cauliflower heads by tying the largest leaves over the heads to keep them tender and tasting mild.
Apply 2 inches of organic mulch around the plants to retain moisture in the soil, prevent weed growth and to keep the soil temperature cool as warmer days approach. Cultivate around the plants to prevent weeds from competing with them. Weed carefully to avoid damaging shallow root systems.
Thin root vegetables grown by seed, such as carrots, to create about 2 inches between them so that they have enough room to reach their maximum size and to allow for adequate air circulation and light penetration.
Monitor plants for diseases and pest infestations, particularly root rot, worms and aphids that are most likely to attack spring vegetables. Remove and destroy plants that become severely diseased. Keep the soil moderately moist, but not soaked to prevent root rot. Pick off by hand and destroy bugs and their larvae as soon as they are noticed. Use a garden hose to spray aphids off of plants until the population diminishes.
Plan accordingly in terms of garden space, particularly if you are also intending to plant warm-season crops. Keep in mind that many spring vegetables will grow into June and sometimes through July if the weather remains mild.