Spring weather is here, but the risk of frost lingers. Learn which hardy crops are safe to plant now and what should wait.
With near record warmth at times in recent weeks, “Spring Fever” has been spreading around central PA. However, experts say not so fast.
Even though it has felt like summer at times, the risk of frost is still very real this time of year, and jumping the gun could cost gardeners their plants.
“It’s tempting when you get a day like this,” said Julie Keene of Flinchbaugh’s Orchards & Farm Market in York County. “But hold your horses. Tomatoes, peppers, cucumbers… I’d really wait until around April 20.”
Julie says one of the biggest mistakes people make is assuming warm temperature swings mean it is safe to plant everything. In reality, a single chilly night can do serious damage; especially to more sensitive plants.
“Frost isn’t the same as a hard freeze,” she explained. “But it can still kill blossoms, and once that happens, you’re starting over.”
What is safe to plant right now?
If you are ready to get your hands in the dirt, there are still plenty of options. Hardy plants actually thrive in cooler conditions and can handle a dip below freezing.
Right now, it is safe to plant:
Vegetables like peas, spinach, kale, lettuce, onions, and radishesFlowers such as pansies, violas, and stockHerbs including thyme, rosemary, and parsley
What plants should wait?
On the flip side, summer crops need much warmer and more stable conditions.
Experts recommend holding off on planting:
Tomatoes, peppers, cucumbers, squash, and melonsFlowers like marigolds, zinnias, and begoniasHerbs like basil and cilantro
For most of central PA, that means waiting until around Mother’s Day, when the threat of frost is much lower.
While many people focus on the 7-day forecast, local experts suggest soil temperature can be drastically overlooked.
For crops like tomatoes, the ground needs to consistently be between 50 and 60 degrees. If it is too cold, plants can struggle to grow even if the air feels warm. Julie says you can check this at home with something as simple as a kitchen thermometer. Just stick it a couple inches into the soil to get a reading.
Another issue this time of year is moisture. After a wet stretch, soil can become too saturated to work with.
To test your soil, grab a handful and squeeze it. If it clumps into a muddy ball, it is too wet. Working the soil in those conditions can lead to compaction, which makes it harder for plants to grow later on.
If you have already planted and a cold night is on the way, covering plants can help but the material matters. Use something breathable like old sheets or burlap. Avoid plastic, which can trap cold and damage plants. The average last frost in the Harrisburg area is around April 21, but freezes have been known to happen into early May.
For now, experts say the safest move is to be patient and keep those summer plants in pots where they can be moved inside if needed.
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