IF YOU HAVEN’T OPENED YOUR PHONE’S WEATHER APP LATELY: IT’S ABOUT TO GET COLD! Yes, we’re just a few days out from the thrills and chills of an arctic blast, and if you have plants you care about in your yard or on your patio, now is the time to prepare them for the potential freeze. Come Thursday evening, areawide temps will start to drop into the subfreezing zone with Friday morning bringing below freezing temperatures and getting as low as the single digits. We’re not expecting a deep freeze like last year (just yet), according to the winter weather advisory, but it is expected to be dry, windy, and the coldest Christmas since 1983.
While many Houston gardeners are already savvy to all the ever-hopeful plant-protecting tricks in the book—using Christmas lights as a heat source, piling plants against the side of the house, and then some—we hopped on the phone with Brent Moon, the horticulture manager at the Houston Botanic Garden to get some basics that are expert-approved. Here are his tips for your own yard.
Make sure the ground is moist around your plants.
Though you might not think so, moist soil holds heat in the ground better than dry soil. “I think it has something to do with the air pockets around it. When the soil is saturated, the soil particles swell up some and there’s just not as much room for air pockets, and so that soil tends to hold heat better. It’s better for the roots of the plant,” Moon says.
Cover your plants like a pro (and for multiple days this time).
The botanic garden’s aim when covering plants is to provide a physical layer of protection against the leaves to trap in heat from the ground to insulate the plants so frost doesn’t form on the plant foliage. In fact, Moon and his team like to form tents or even tepees around the plants using feather-light frost cloth, which you can cut to specific sizes to address your needs. “To cover an entire bed of shrubs low to the ground, we’ll cut a piece that’s 20–30 feet long and eight to 10 feet wide and pin it down using what we call sod staples.”
You can find frost cloth at most nurseries—“and Home Depot and Lowe’s sell a product called the Planket,” Moon says—to replicate the process, or you use old bed sheets. “If you can pin the fabric to the ground, that helps trap that heat the ground has absorbed in the days prior to the cold coming—it’s almost a mini greenhouse effect.” You’ll also want to keep those plants covered for multiple days (per the latest forecast).
A few more tips: If you only have blankets, just beware the weight of them, as they could crush the plant underneath. Keep an eye if it rains, as the weight of a sheet could also become a problem for the plant. And do not use plastic or trash bags to cover plants, warns Moon. “Let’s say the sun comes out the next day and you’re not home or paying attention, that can heat up really quickly and burn the foliage of your plant.”
For tall plants, something is better than nothing.
Though Moon and his team often use bamboo to make teepees around taller shrubs or plants, when you can’t reach the top of a plant on your own—“let’s say you have something like a brugmansia,” Moon says, “or something very sensitive”—you can also just wrap the foliage and the trunks in a spiral pattern, if you can’t do a full-on tent-style covering. “That’s still better than nothing.”
Try piling leaves and mulch around sensitive plants.
“Especially things like limes and lemons—they’re our most sensitive citrus,” says Moon. “Sometimes they can get killed to the ground when we have an extended freeze.” Piling up leaves and mulch around their trunks helps insulate and protect them. Just rake it all away when the weather lets up.
Bring those potted plants inside, of course.
Today is the day to just go ahead and bring in all the tropical and tender plants you have in pots and hanging baskets, from plumerias to bromeliads to succulents. “You can leave them in your home or garage for a couple days and they’ll be okay,” Moon says. After that, you might start noticing they’ll drop foliage due to a lack of light. “I try not to leave them inside any longer than I have to.”
Reassess your yard.
“There are plants that are fully hardy here,” Moon says. Common landscape plants like yaupon hollies, pittosporum, wax myrtles, camellias, and azaleas can usually tolerate freezing temperatures, though they may be very susceptible to tip damage and have their blooming season abruptly ruined. Take camellias, for instance; since some are already in bloom, due to an otherwise mild season, they may be at risk of losing their buds and flowers to the freeze. “You may just want to go ahead and cover them.”
And while plants with a tough bark are typically going to be okay during a cold spell, beware the ones that look woody but are really tender, like the natal plum, ixora, or hummingbird bush (hamelia patens). “Sometimes those can die on the ground,” Moon says. The good news: “Since they are root-hardy, they will bounce back.” And who doesn’t want a zombie plant?
At the end of the day, “Don’t freak out too much,” says Moon. “There’s only so much we can do to protect our plants. Either bring them inside, or cover them and hope for the best.”