Planting early in spring not only allows you to have fresh vegetables before the last frost is past, it also allows you to grow vegetables that don't thrive in the warm summer months. Cool-season vegetables thrive during the warm days and cool nights of spring. Summer heat often causes the plants to quickly set seeds, ruining the crop. Start the vegetables even earlier by planting inside in late winter, then transplanting them out to the garden in spring.
Lettuces and Leaf Vegetables
Both leaf and head lettuces grow best during cool temperatures. Head lettuce must be ready for harvest before summer arrives, but many leaf types can be harvested from mid-spring until midsummer. Spinach and Swiss chard also thrive in the spring garden. Except for head lettuce, all leaf vegetables can be harvested weekly as long as just the crown of the plant is removed, producing a consistent crop over a period of several months. Plant lettuce and leaf vegetables as soon as the ground thaws out enough to work in early spring.
Broccoli, Cauliflower and Cabbage
Broccoli, cauliflower and other members of the cabbage family produce a fully mature crop in as little as two to three months. These plants grow best during the cool spring months, as warm weather causes them to go to seed. Cabbage family plants prefer daytime temperatures between 60 and 70F, and are planted outside as soon as these temperatures are reached and maintained in spring. They tolerate nighttime frosts with no damage, but prolonged periods of daytime temperatures below 50F can stunt the plant's growth.
Another quick maturing crop, peas complete their growing season by early summer. Plant these vegetables as soon as the ground thaws enough to work it in early spring. Nighttime frosts do not harm the plants, but too much warmth does. Once the pods begin reaching maturity, frequent harvesting encourages the plants to set new pods until warm weather.
Onions don't reach maturity until mid- to late summer, but they must be planted in early spring. Plant either seeds or sets as soon as you can work the ground in early spring. Frost doesn't damage the young plants. Onions require a long growing season and only reach full maturity when planted in early spring. Leeks and chives, both members of the onion family, must also be planted early in the season.
Carrots grow well in both spring and summer. They germinate well from seeds and quickly reach maturity, so early spring planting allows you to plant several crops up until fall frost. Sow carrots as soon as the ground begins to thaw, then plant subsequent crops as soon as the first early spring harvest is in. When mulched, carrots survive well in the ground into the winter months.