IF YOU HAVEN’T OPENED YOUR PHONE’S WEATHER APP LATELY: IT’S ABOUT TO GET COLD! Yes, we’re just a day 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 of light freezing rain and ice pellets. Come Thursday morning, areawide temps will start to drop into the 30s with Friday bringing below freezing temperatures. We're not expecting a deep freeze like last year, according to the Winter weather advisory, but it is expected to be cold with Houston-area temps as low as the upper-20s.
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’s 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,” says Moon.
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 so frost doesn’t form on the plant foliage and to trap in heat from the ground to insulate the plants. In fact, Moon and his team like to form tents or even tepees around the plants using feather-light frost cloth, which they can easily cut to specific sizes to address their 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,” says Moon—to replicate the process, or you use old bed sheets. “If you can pin the fabric to the ground,” says Moon, “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 a trash bag 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,” says Moon, “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,” Moon says. “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. When the cold spell is done, you can 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,” says Moon. 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,” says Moon. 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, says Moon, “Don’t freak out too much. There’s only so much we can do to protect our plants. Either bring them inside, or cover them and hope for the best.”