Warm Season Vegetables
Warm-season vegetables are those which are most easily damaged by cold temperatures. For this reason, they are planted outdoors only after the last chance of frost in the spring. Warm season vegetables include tomato, pepper, eggplant, corn, cucumber, winter squash and melons and many more.
Which vegetables can grow in your area is determined by overall climate. The most important factors include average first and last frost dates, extremes in summer and winter temperature and the climate-modifying effects of windbreaks, hills, lakes etc. which determine how rapidly temperatures will change.
For the Richmond area, our average last frost date is April 20 and the first killing frost date is October 30. That gives an average growing season of around 202 days which is long enough to produce most vegetables.
One of the biggest reasons for vegetable garden failures is planting too soon or too late. Planting time for some vegetables can be critical because they need warm temperatures and also require a long growing season (80-100 days) to produce fruit. Long season vegetables include asparagus, dry beans, Brussels sprouts, celery, garlic, melons, onions, hot peppers, pumpkins, shallots and sweet potatoes.
Temperature extremes in the summer and winter often dictate the degree of success. For warm season vegetables, hot conditions generally are favored for fruit development. However, extremes in heat during the period when the plants are in flower and ready to set fruit (pollination) are not good. Tomatoes, peppers and eggplant may produce very little fruit if planting is delayed or summer heat in the 80s comes very early.
Gardeners should also consider microclimates which are small areas of climate within larger climates that can be quite different. Slope, wind direction, sun exposure and bodies of water can modify the climate of the local area and extend or decrease the growing period. Around the home, many different microclimates may exist. The soil on the north side of the house is cooler and wetter than on the southern or western side because of the lack of direct sun exposure. Therefore, planting on a northern exposure may be acceptable for cool-season vegetables, but quite limiting for warm-season vegetables. Likewise, low areas on a site tend to collect cold, heavier air and these planting beds would also be slow to warm. This would affect tender warm season vegetables which may be damaged by cold spells in the early spring. When you select a site to plant, consider the potential for microclimate differences.