Category Archives: plants

Basil plants for sale in March in Northern Virginia

A lot of us are just itching to start seeds, purchase plants, and start gardening as soon as possible. It is important to know that some plants need warm summer weather, while others thrive in cool spring temperatures. Also, just because it is for sale does not mean that you should sow the seed now or plant the plant in your garden.

First, learn which of your plants/seeds are cool season versus warm season plants. Second, identify your average last frost date so you can figure out your starting time.

Cool season plants thrive in March and April. They can tolerate a cold nip at night. By summer, they may have disappeared, gone to flower, or died back. In the DC metro area, March and April are cool season months and this is when we can plant/sow seeds of spinach, lettuce, cilantro, and kale outside. However, if we were to plant a warm season plant such as tomatoes and basil outside, they would not survive a frost. Warm season plants have to be planted after the danger of frost has passed and the night temperatures are constantly in the mid-fifties. Usually they will do well in the summer, from May until our first autumn frost. You can start the seeds of basil and tomatoes indoors in April under lights where they will stay warm and toasty until you bring them out when it is warmer.

From winter to spring, the chance of frost diminishes. Although some gardeners will plant their warm season plants in mid April, there is still a slight risk of a frost. There is no risk in May and some gardeners use Mother’s Day as a marker for when they can safely plant warm season plants in the garden.

Tomato plants for sale in March in Northern Virginia

Many hardware stores and garden centers will sell plants as early as March, including basil and tomatoes.  People assume that because the plant is there for sale it is okay to plant it in the ground.

Frost is predicted when air temperatures reach 32 degrees. It also may occur when air temperatures are just above freezing due to open exposure to the clear night sky. Frost can be a “light freeze” at 29 to 32 degrees, which usually kills tender plants. Using the 1991-2020 climate normals from the National Oceanic and Atmospheric Administration, the National Gardening Association provides a useful chart outlining probabilities of cold temperatures by dates.

By entering my Northern Virginia zip code, I can see that March 29 is the point where there is a fifty-fifty chance of frost occurring. Some gardeners look for this point to get a head start knowing they may have to cover their plants.  I am more interested in being safe than sorry  — I have no desire to rush out and cover my plants so I am looking for a number lower than 50. Also, the National Gardening Association recommends using 36 degrees as the marker because frost can form at 32 degrees and then fall down into your garden even though it is 36 degrees on the ground. Using this logic, the 50/50 mark is April 9.

On April 10, I have a 10 percent chance of 32 degree temperatures. Ten days later, I have a 10 percent chance of 36 degree temperatures. As time goes by it, the 10 percent chance of frost will diminish to zero (until autumn). Because I am a low risk taker (or possibly too lazy to go outside and cover my plants), I am shooting for less than 10 percent to near zero. Therefore, I can plant basil and tomatoes at the end of April with a slight risk of frost to Mother’s Day when there is no risk.

At this point, when to plant is a personal preference and it also depends on your schedule, your available time. But don’t sow your tomato seeds now and do not plant tomatoes in the garden in March!