Average Last Spring Frost

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Q:  When is the last chance for frost this spring?

 A:We all know the weather can be very hard to predict, especially in North Carolina. We have had a usually warm early spring but are now seeing some colder temperatures this week. As we have warm temperatures, many gardeners get spring fever and want to get started on their gardens and landscapes. One of the challenges gardeners face is when to plant warm-season flowers and vegetables and not risk cold damage from a late frost.

Frost forms on solid objects when the water vapor in the atmosphere changes from its vapor (gas) phase to small ice crystals (solid phase). For frost to form on an object, the object has to reach 32°F or lower. However, the air temperature within the vicinity of the object can be several degrees higher. It does not take long to realize it can be very hard to predict when our last spring frost will be, especially as we have warm spring days and cool nights.

There is lots of variation in the date when we have our last frost in Wayne County. The last frost date has been as early as mid-March and some years as late as the beginning of May. Often many resources give gardeners a guideline by finding the average last frost date. Even though it may sound simple enough to take the average of all the last frost dates over the years, there is much variation in what resources claim as the last average frost date. In doing a search of what different resources say is the average last frost date for Goldsboro, it ranged from March 28th to April 20th. The ranges vary depending on how many years of data are include in the average and takes into consideration how often it does not occur on that average date. We often pick somewhere in the middle and say around April 15th is the last average frost date in Wayne County. Remember, however, there is no guarantee that there will not be a frost after April 15th.

So what is a gardener to do when they are ready to plant warm season vegetables, like tomatoes, peppers, eggplant, corn, beans, and squash, or warm season flowers like begonias, impatiens, marigolds, petunias and zinnias in their garden? It all depends on if you want to be a risk taker or play it safe. Some gardeners go ahead and start planting warm-season flowers and vegetables around the first of April knowing that they could lose their plants to a late frost, while others wait until around late April or early May when the chances of frost are much lower.

If you do plant early, you have to be prepared to cover and protect your plants if we do have a late spring frost. Row covers made of light-weight fabric that will be sun and air permeable work well for quickly covering plants if a frost is predicted. Many try to cover plants with plastic because it is often what they have on hand for a last minute solution. Plastic covers usually create more plant damage than good. Plant leaves in direct contact with the plastic can be burned and if the plastic is not removed early in the morning, you are creating a mini-greenhouse that will quickly over heat your plants and not allow air to get to them. Creating a tunnel using wire or PVC pipe and then covering with row covers or plastic can help prevent plants from coming in direct contact with the material. When covers are used they should be removed the next morning as temperatures increase to prevent further plant damage.

As you plan for planting your gardens and landscapes keep in mind that we are not necessarily out of the clear for having a late spring frost. We never know if we have already seen our last frost for the season buts we can always hope that we have seen the last of cool weather this season.

For your garden and lawn questions contact the Wayne County Extension Master Gardener Volunteer Plant Clinic on Mondays and Wednesdays from 10 a.m. to 1 p.m. The plant clinic is a free resource to Wayne County residents. One can reach the Wayne County Extension Master Gardener Volunteer Plant Clinic by phone at 919-731-1433, e-mail at Master.Gardener@waynegov.com, or stopping by Room 100 of the Wayne County Extension Office (208 West Chestnut Street, Goldsboro). People contacting the plant clinic can also pick up soil testing kits and garden extension publications.

Learn More!

Jessica Strickland is an Agriculture Extension Agent, specializing in horticulture for North Carolina Cooperative Extension in Wayne County. Horticulture program information can be found at http://wayne.ces.ncsu.edu/. Forward any questions you would like answered from this week’s column to Jessica.Strickland@waynegov.com.

 Upcoming Wayne County Extension Gardening Programs

  • Save the date for the annual Spring Garden Festival & Plant Sale! This year’s event will be held on Saturday, April 23rd at the Wayne County Extension Office (208 W. Chestnut Street, Goldsboro). The Wayne County Extension Master Gardener Volunteers have a great event planned with gardening demonstrations, children’s activities, along with many great plants for sale. Volunteers will also be on hand to answer your gardening questions along with having publications and soil test kits available. Doors will open at 9 a.m. and stay open until noon.
  • ‘Ask a Master Gardener’ Clinics in April. Wayne County Extension Master Gardener Volunteers will be holding several ‘Ask a Master Gardener’ clinics at local events in April. Stop by their booth to get answers to your gardening questions along with picking up publications and soil sample kits. Visit them at the following events:
    • Home & Garden Show – April 16th from 10 a.m. to 2 p.m. and Sun. April 17th from 1 to 5 p.m. at the Wayne Regional Agriculture Fairgrounds
    • Garden Center on Seymour Johnson Air Force Base – April 30th from 11 a.m. to 1 p.m.
    • Wayne County Reads Festival at Herman Park – May 1st from 1 to 5 p.m.