Many people are enjoying this unusually mild weather and some are eager to begin planting summer flowering plants and vegetables. However, even with the warm temperatures, the risk of a late season frost has not passed. The average last date of frost in our area is usually around April 15. Planting anything that is not cold hardy prior to that date puts it at risk of suffering freeze damage.
Most spring flowering shrubs and trees, such as fruit trees, set their buds in the late summer and fall of the previous year. The unopened buds have a greater resistance to the cold temperatures. However, newly opened flowers and young tender vegetative growth are susceptible to freezing temperatures. Peaches, apples and blueberries, major commercial fruit crops in Georgia, are among the earlier flowering plants and can be damaged by freezing temperatures. Saucer magnolias, Bradford pears and cherry trees can suffer the same fate.
On Easter Sunday in early April 2007, a late season frost occurred with temperatures falling into the 20s. The frost extended well into the southern part of the state. A majority of the fruit crops were lost. These trees did not bear fruit since their flowers were damaged. This prevented the pollination process that leads to the setting of the fruit. The freeze also caused harm to plants in the home landscape. Although the new growth and flowers were harmed by the cold, most of these plants survived and produced new growth later.
The Extension office received numerous calls from people who had planted tender vegetable plants, like tomatoes and peppers, as well as herbaceous flowering plants, that suffered freeze damage. They wanted to know what could be done to save their plants. The homeowners were advised to remove and dispose of those plants. They were most likely dead and should be replaced after all danger of frost has passed.
If a late season freeze is forecast, young tender plants with new growth and open flowers can be covered with a sheet or plastic cover to give some protection. However, this action does not guarantee the plants will survive freezing temperatures. Remove the covering the following day.
Avoid planting cold sensitive plants until after the danger of frost has passed in the middle of April. Plant seeds, like squash, cucumbers, beans and peppers after May 1 when the soil temperatures are warmer. Before then, the colder soil temperatures may delay germination of these seeds. You can start the seeds indoors in small containers, such as peat pots, and then plant them outdoors. Transplant seedlings can also be purchased at local garden centers.
Even though you may be tempted to put out tender plants, the risk of subfreezing temperatures is not over. Take this into consideration when planning your garden. Wait until the danger of a damaging cold snap has passed before planting plants that are not cold hardy.