Don't rush planting season; early spring calls for hardy plants [Master Gardener column]

When eager for spring, it’s easy to make a mistake and rush the growing season. We’ve all done it — planted a flat of annuals like coleus or impatiens in April, only to find them wilted and brown after an unexpectedly cold night.

Other damage might not be as readily apparent. For example, heat-loving tomatoes or peppers may survive when planted in the garden in cool spring weather, but will not thrive like their counterparts that were held up until the weather is sufficiently warm. Read on for tips on how to deal with erratic spring weather.

Pick hardy plants for early spring

Beautiful annuals to plant in containers or the ground in early spring include pansies, snapdragons, sweet alyssum and sweet peas. Vegetable counterparts for chilly spring weather are beets, cabbage, peas and many types of greens. These plants can withstand light frosts. Many perennials and herbs can also be planted in early spring.

Wait until the soil has warmed and the danger of frost has passed.

The tricky thing about spring is that the air might seem very balmy, especially during the day, but the soil takes longer to warm up. For most popular summer plants, the soil temperature should be above 65 F. How to know? The best way to measure is with a soil thermometer; however, in a pinch, a meat thermometer with a probe should work. Just make sure to clean and sanitize it before using it again with food.

In Lancaster County, Mother’s Day is still a good “all-clear” date for when frost will no longer occur. Keep in mind that frost can form when the air temperature is below 36 F, since colder air settles near the ground.

How to protect plants from frost

If you took a risk and planted tender plants a bit early, you could cover them when a frost warning is announced. For a temporary solution, a sheet or blanket is best; it will trap warmer air near the plant. Never cover a plant with plastic that directly touches the foliage, since this creates condensation that will freeze the plastic to the plant. Always uncover the plant the morning after a freeze warning.

Harden transplants for success

No matter how warm the temperature is, a plant always benefits from transitioning gradually from a protective greenhouse to the outdoors, where wind, sunlight and fluctuating temperatures take their toll. Hardening, or hardening off, is a gradual introduction of outdoor stresses that help the plant accumulate carbohydrates, trigger more root development, reduce the amount of freeze-prone water and thicken the plant’s cell walls.

This process is done by moving the plant outdoors for increasingly longer periods per day in a protected spot, such as a porch, and by diminishing the amount of water. For details, see the informational web page, “Hardening Transplants,” at extension.psu.edu/hardening-transplants.

Penn State Master Gardeners are an excellent resource for questions about planting times and conditions in Lancaster County. For answers to these questions and others, please reach out to our Garden Hotline at Lancastermg@psu.edu or 717-394-6851.

Lois Miklas is a Penn State Master Gardener for Lancaster County, and a former area Master Gardener coordinator.

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