Charlotte Glen, Horticulture Agent

Our mild winter has rapidly turned into an early spring, leading many gardeners to wonder if it is safe to plant frost sensitive vegetables like tomatoes, peppers, cucumbers, and squash outside now. For some crops the answer is yes, but be prepared to protect them if temperatures near 32 degrees are predicted. For others, even though our days have warmed soil temperatures are not yet quite warm enough for them to grow well.

Okay to Plant Now

In a typical year, coastal areas in our region can expect the last spring frost to occur around March 30, while inland areas often experience light frosts as late as April 15. This year, warmer temperatures seem to have set in early. As a result soil temperatures throughout southeastern NC have already reached 60 degrees or more, making them warm enough to plant many summer crops outside. Though unlikely, frost can still not be ruled out, so if you do plant early have a plan to protect sensitive crops by covering them with old sheets or floating row cover, especially during the next few weeks.

Corn is one of the most cold tolerant of the warm season vegetables. It can be seeded in the garden now with little concern for potential frost damage. Green beans and butter beans can also be seeded directly in the garden now. Both bush and pole varieties are available. Bush varieties are more convenient because they do not require trellising for support, though pole varieties tend to be more productive.

If you are prepared to protect them from frost, you can set out squash, zucchini and cucumbers now as seed or small plants. When seeded direct in the garden, these vegetables are often planted in hills, with 3 or 4 seed planted on mounds spaced 2’ apart. Floating row cover or old sheets work well to protect young plants from frost down to 29 degrees. When covering plants, make sure covers extend all the way to the ground to trap in heat from the soil.

Tomatoes are more tolerant of cool temperatures than their relatives, peppers and eggplants. When setting out tomatoes, plant them deep, so the first couple of inches of the stem are covered with soil. Because tomatoes produce roots along their stems, deep planting results in a stronger root system. If you have found tomatoes difficult to grow in your garden because of diseases that cause them to wilt and die, your best option is to try growing them in large containers filled with potting soil, since most wilt diseases live in the soil and cannot be treated. Beginning gardeners should definitely try cherry tomatoes, since they are the easiest to grow.

It is also not too late to plant some quick maturing cool season crops. These include lettuce, spinach, radish, mustard greens, turnips, and spring cabbage. Cauliflower and broccoli planted in spring have a tendency to bolt (go to flower) in spring and grow better in our area as fall crops.

Wait to Plant These Crops

Even if we don’t experience another frost, soil temperatures have not quite warmed up enough for some of our heat loving summer crops. In addition, all of these crops are extremely frost sensitive so if a frost occurs in the next few weeks they would be sure to be damaged. My advice is to wait a few more weeks before setting out pepper, eggplant or basil plants, though they could be planted in containers gardens now if they can be moved inside when temperatures below the mid 30’s are predicted. Watermelons, cantaloupes, and okra can be planted in the garden as seed or young plants, but do best after soil temperatures have reached at least 70 degrees, which will probably take a few more weeks.

Southern peas, which include field peas, black eye peas and cow peas, along with peanuts, need warm soils to grow well and so usually are not seeded in the garden until late April. The same is true for sweet potatoes, which are set out as rooted cuttings or slips. While all vegetables need well drained soil to do well, it is especially important to have excellent drainage to successfully grow peanuts and sweet potatoes.

Learn More

• Vegetable Fact Sheets from Clemson Extension: http://www.clemson.edu/extension/hgic/plants/vegetables/crops/