When is best time to plant? Master gardener discusses ‘killing frost’, soil temperature for successful planting

Master gardener Elaine Specht holds one of the hyacinth beans she is potting outside her home in Woodstock. Rich Cooley/Daily

WOODSTOCK – ‘Tis the season to be growing, and Master Gardener Elaine Specht says now is the time to work smarter, not harder.

Part science and part luck, deciding when to plant is one of the biggest decisions gardeners have to make.

“Just because temperatures are rising, don’t be fooled into planting too early due,” Specht said. “Each region of Virginia is different. Even within a specific area, like here in Woodstock, the planting season can fluctuate.”

For most of the Northern Shenandoah Valley,  the best time to begin planting is after Mother’s Day to prevent what is known as a killing frost – a term used to define the occurrence of temperatures cold enough to kill even the hardiest of plants.

“Most perennials and root crops can’t survive below 28 degrees,” she said.

It’s possible the area could see another rogue freeze or two, which Specht said makes it difficult for gardeners to predict when to plant.

Some gardeners plant out of necessity, while others plant out of passion. For gardeners willing to take the risk, planting before Mother’s Day could risk half if not all of the crop.

“Most people will wait,” she said. “And follow the Mother’s Day rule. It’s better to be safe than sorry.”

Specht suggests covering tender plants to protect them from frost.

Hardier plants like shrubs, perennial flowers like pansies and cold-weather vegetables like onions can tolerate colder evenings.

While the arrival of spring has many gardeners itching to get out into the garden, another factor plays into its success: soil temperature.

“Soil temperature determines the required germination for various plants and crops,” Specht said. “Seeds will rot in the ground if the temperature is not sufficient enough for their growth.”

Some examples of soil temperatures that some plants need:

  • 50-65: lettuce, spinach and peas
  • 65-85: Tomato, squash, beans and peppers
  • 50-85: Carrots, broccoli and cabbage

“The most important thing to remember before planting is to make sure that the frost date has passed if not cold-hardy,” she said. “Otherwise, they won’t make it through the season.”

Many gardeners begin germination indoors, under a controlled environment.

“For gardeners that want to start their germination early, they always have the options of starting their gardens indoors,” she said. “Which is actually very common and easy.”

Spect said seed germination requirements for individual plants could vary. “After germination, when the seed is established, it can be planted outdoors.”