Houston Matters

How to save plants after a hard freeze

The Houston area was hit hard by a deep freeze during the holidays. Experts say there are easy tests to determine if your plant is still alive and can be saved.

Plants in cold weather
Daisy Espinoza / Houston Public Media
Plants that survived the freeze may need extra attention to ensure they bloom again.

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A couple of days of sustained freezing over the holidays might not have been bad as February 2021, but it was enough to require extra care to outdoor plants. Meg Tapp from the Garden Club of Houston spoke to Houston Matters on Thursday on how to identify if your garden suffered during freezing conditions.

“If it’s woody, like a shrub or a tree, that’s going to take a little bit longer to see if it’s a goner,” Tapp said. “If it’s any kind of soft plant without a trunk or branches, feel it. And if it’s mushy, cut the mushy part off, because it could still be alive. But the mushy will continue and move down into the plant and make it worse, so that you want to take care of today.”

If it’s a woody plant like a tree or shrub, leave it alone for now, Tapp said.

“Because believe it or not some, like the birds and things in the garden, actually need it to be like that; it does help the whole ecosystem of your garden, they need the dried leaves and everything,” Tapp said. “And also you don’t really know how much damage it’s sustained. Because when it’s when it’s got that hard bark, even if it’s a tiny little twig, it had protection. So even though the leaves all look horrible, you just need to leave it alone for a little while.”

Tapp said cutting a woody plant too early could be damaging also because it is early January and there could potentially be more cold weather. There is a way to test trees and shrubs for damage: the scratch test.

“You can take your knife or just your fingernail in scratch on the trunk. So what you’re doing is taking just the outer layer of bark, I mean, it wouldn’t work like on an oak tree, you’d have to get something bigger,” she said. “But if it shows green under there, that’s the first layer, and if it’s green, then it is alive.”

Another way to check is by cutting a twig off, “and if you look at the middle, you know like when you look at a tree and it’s got the rings, if you look at it and you see a hole down the center of what you’ve just cut off, that meant that’s gone because it froze and it’s lost its ability to feed itself.”

Tapp also suggested if gardens need to be re-sodded to go with organic fertilizers.

A hibiscus plant that weathered sub-freezing temperatures in Houston in December 2022.

If there is another freeze, or cold, plant-damaging weather in the future, Tapp said it’s best to prepare for the cold weather by covering the soil where it meets the plant.

“So you water the plants for sure, everybody needs a good drink before they’re about to go through that stress. And then the main thing is to guard where the plant hits the soil,” she said. “If that can stay alive, then even if it dies on the top, if you can cut it all the way back and the roots are still alive and the bottom of the trunk is still alive, so it will regrow.”

She said insulating the plant with mulch to keep the heat in is best.

“You can put honestly like a foot of mulch if you felt like it, but that what you’re trying to do is keep all the heat in, and so you do cover your plants,” she said. “But if it’s something too big to cover, then just wrap the base of the whole plant where it hits the the soil. Wrap that really well you can take bags of leaves and just pile them up. You can take insulation, you can take blankets, you can take anything that you can to protect that area.”

She warned not to use plastic because if it touches the plant while in freezing temperatures it can harden, and damage the plant. Soft insulation is best, she said.

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