Final Frost Date & Gardening Tips

MAY 06

"Clear moon, frost soon" is the old farmer's adage for predicting frost. This indicates that if the atmosphere is clear, there is no blanket of clouds to trap the heat radiating from the earth's surface. If the night temperature is low enough, and there is no wind, frost may form on such a clear night. Nowadays, we can rely on a more advanced system for predicting frost. Each year a range of local data is collected to predict the first and last frost dates for a region. The last frost date in the spring and the first frost date in the fall dictate how long the growing season will be, allowing us to plan our gardens accordingly. There are several determining factors used to calculate the final frost and first freeze date for our area. Changes in climate, wind, elevation, proximity to buildings and water can affect the likelihood of frosts. For example, as estimated by the Maryland Department of Agriculture, Frederick's final frost date (meaning there is only a 10% chance of frost on or after the date) is April 29th.  (For more frost dates for the Maryland region, check with the University of Maryland Extension.)  Some gardeners traditionally wait until Mother's Day to begin planting vegetables and annuals, but as long as we've passed the final frost date, it's safe to plant. In any case, the best advice is to keep a close eye on the weather forecasts. In the event that winter has trouble letting go of its reign, here are some tips for protecting your plants from unexpectedly cold weather:

  • If frost is predicted, the time to protect your plants begins at night and ends in the morning. An easily remembered rule of thumb is to cover your plants at 8pm and uncover them at 8am.
  • Plants can be covered with lightweight, breathable material like bed sheets, table cloths, light weight towels, burlap, etc. If needed, you can also cover your plants with over-turned buckets or bins.
  • It is critical to remember to uncover your plants in the morning. Your plants need to breathe. They also need exposure to sunlight.
  • Frost damage will be noticeable within a few days. New growth will discolor, drop off or turn to mush. Buds will not open and may drop off. Sometimes new growth will reappear after a week or two, but in some cases you may have to start over.

As we are beyond the final frost date in most areas, we can be more confident in preparing and planting our gardens, vegetable beds, and annual containers. So prepare for the full force of spring to be upon us, roll up your sleeves, and get digging in that dirt!