Determining what vegetables are early planting vegetables requires understanding what temperatures the vegetables prefer. Gardeners can plant cool weather crops such as lettuce, kale, spinach, carrots, cabbage and potatoes in a cold frame in March in most USDA zones. With the use of frost cover and a tunnel house, it is possible to grow cool weather crops year-round. A tunnel house is an unheated plastic-covered tunnel shaped structure similar to a greenhouse.
Begin With Greens
When asking what vegetables are early planting vegetables, greens come to mind. Lettuce, kale, spinach, arugula, endive, mizuna, Swiss chard, mustard greens and turnip greens are some of the most popular cool weather crops in this category.
It is best to grow these crops in a cold frame so they have some sort of protection from the elements outdoors. Direct sow seeds of these crops inside the cold frames or if you prefer, plant young plants that have been hardened-off inside the cold frame and use frost cover for additional protection from the cold weather.
It is possible to direct sow seeds of these crops as early as January, however waiting until mid-March will insure the worst of the winter weather is over.
Root vegetables covered with some type of protective mulch such as straw will often survive the entire winter outdoors, making them the perfect candidate for early planting. If you are wondering what vegetables are early planting vegetables in the root vegetable category, beets, onions, rutabaga, carrots, potatoes, turnips, leeks and radish all qualify.
Most root vegetable crops are direct seeded. Pre-sprout potatoes before you plant them. Follow the instructions on the seed potato package. You can buy onion sets, which are small bulbs you plant directly in the ground. It is also possible to grow onions from seed either by direct sowing, or by starting the seed early in the house.
Crop Protection Techniques
If you intend to get a head start on the gardening season, there is more to know than just what vegetables are early planting vegetables. Some crops will do just fine outdoors with no protection at all late in spring; however, crops started when there is still snow on the ground need protection. Using these crop protection techniques it is possible to plant warm weather crops such as cucumbers, tomatoes and eggplants in late March or early April directly in the garden in USDA zone 5 and higher.
Cold frames--small boxlike structures made of wood, plastic, glass or straw bales--are the simplest to construct. If straw bales are used, once there is no longer a need for the bales to be used to protect plants, the straw can be used as mulch in the garden or even used in walkways to keep weeds down.
Tunnel houses are another popular option, especially with market gardeners. Tunnel houses are larger than cold frames. Most tunnel houses are unheated although it is possible to heat them if they are large enough.
Frost cover, sometimes called row cover, suspended above the plants will add an extra layer of protection. Frost cover is made of either lightweight polyester or polyethylene fabric. It can be used alone, without a cold frame or tunnel house, later in the season as the weather warms up to keep unexpected frost off of plants.