North Carolina gardeners can take advantage of the different temperatures throughout spring, summer and fall to produce a wide assortment of vegetables. Each of these seasons offers distinctive benefits for various crops, but knowing what to plant at particular times is pivotal in getting the most fruits from your labor. The planting times differ in the state's three regions -- coastal plains, piedmont and mountains.
Sweet corn (Zea mays var. saccharata), tomatoes (Solanum lycopersicum) and cucumbers (Cucumis sativus) are examples of tender crops that grow best in summer's hot temperatures. These plants must be planted and mature between the last frost of in spring and the first frost in autumn.
Several tender, warm-season crops have long growing seasons. Many watermelons (Citrullus lanatus), for example, reach maturity 85 days after their seeds are sown; sweet corn typically takes 60 to 90 days to mature.
Most leafy and root crops grow better and produce better-tasting crops when grown in the cooler temperatures of spring or fall and sometimes in winter. These crops are considered semi-hardy or hardy.
Kale (Brassica oleracea var. sabellica), a cole crop, actually produces sweeter leaves when hit with frost or even snow. Other cole crops such as collards (Brassica oleracea var. acephala), cabbage (Brassica oleracea var. capitata) and broccoli (Brassica oleracea var. italica) also perform well in cooler temperatures. Root crops include carrots (Daucus carota) and radishes (Raphanus sativus).
Temperature -- both soil and air -- plays a pivotal role in the planning of a vegetable garden. The location's first and last average annual freeze and frost dates also come into play, particularly for tender vegetables.
Different seeds germinate better in different soil temperatures. Although you can often skip measuring your soil's temperature and rely on average planting dates for certain vegetables, knowing the soil temperature can prove beneficial and help ensure your crops perform well. The way to measure soil temperature is to insert a soil thermometer about 3 to 4 inches into the soil and wait for the reading. Many cool-season crops germinate best when the soil temperature is between 45 and 85 degrees Fahrenheit, and many hot-season vegetables germinate when the soil temperature is 60 to 95 degrees Fahrenheit.
Although many cool-season crops thrive in early-spring temperatures, North Carolina's temperatures rise quickly during spring and may not provide the best environment for cool-season crops such as lettuce (Lactuca sativa), which tends to bolt in hot temperatures. Bolting is when a plant goes to seed quickly; often it produces a bitter or otherwise off-putting flavor.
Choose spring-planted, cool-season crops that have a short amount of days from the time their seeds are sown until they are ready to be harvested, ensuring they will be mature before the growing season's hottest temperatures. Plant most of the cool-season crops as soon as the soil is workable.
Plant summer vegetables after the last chance of frost has passed in your location and soil temperatures reach at least 60 degrees Fahrenheit.
Throughout the state, July and August are usually reliable planting months for fall harvests, particularly for slow-growing crops with a large number of days between seed sowing and harvest. The average first killing frost ranges from early October in western North Carolina to early or late November near the Atlantic Coast.
For tender vegetables, subtract the "days to harvest" listed on their seed packets from the average first killing frost date to find your ideal planting date. Cool-season crops, including kale and leaf lettuces, can go in the ground from August through Sept. 1 in the piedmont; plant seven to 10 days earlier in western North Carolina and seven to 10 days later in eastern North Carolina.