Each plant prefers a certain range of temperatures. Tropical plants grow best at temperatures around 30-35C while temperate plants prefer temperatures around 20-30C. Plants generally grow slowly in winter because it is too cold, dark and wet. Seeds germinate more slowly in cold soil than in warm. Rates of germination can be improved in winter by using cold frame. Seedlings grown in a cold frame are then ready to be planted out when warmer weather arrives. Seedlings should be planted out as soon as weather conditions are suitable.
Frosts damage some plants. Tomatoes are very susceptible to frosts. If grown in frost-prone areas they need protection. To ensure success you should refer to the seed packet or a gardening guide for the recommended sowing times.