Dealing with plants after the freeze.
Take some time to assess damage to plants before cutting things back
The snow’s melted, temperatures are back to normal and blackouts are rolling no more. Now’s the time to head outside to figure out what plants in your landscape survived, what needs help and what’s ready for the compost bin.
Last week’s arctic blast set record lows on three consecutive days, dropping into the single digits several times and remaining below freezing for hours on end. The effects are apparent everywhere you look: plants splayed on the ground as if knocked senseless by the cold, their color faded like a bad Instagram filter and leaves blackened, curled and crispy.
“Every freeze event is different, but this one was historically extreme,” said Andrew Labay,
director of horticulture at the San Antonio Botanical Garden, as he prepared to assess the state of the 33-acre facility. “We haven’t seen temperatures this
low for so long in more than 30 years.”
Actually, it could have been worse. Many plants will survive thanks to the snow that insulated them from the brutal temperatures. And there wasn’t much sleet or freezing rain, so we didn’t have the kind of ice buildup that can take down even the strongest tree limbs.
Still, the cold is likely to have killed or damaged plenty of bedding plants, bushes and trees. Winter storms kill because, when temperatures drop below freezing, the water in plant tissue turns to ice, bursting cell membranes. When temps drop as low as they did last week, even native plants are at risk.
This kind of extreme cold can also damage a plant’s vascular system, which transports water and nutrients throughout the plant body. The damage may may not show itself for weeks or even months, especially in trees.
While your initial inclination
may be to head outside and immediately begin trimming and pulling, in most cases, experts instead advise patience.
“Homeowners would be wise to assess the damage first and then wait a week or two before taking any action,” said Bob Webster, co-owner of Shades of Green on Sunset Road.
While the tops of many plants have died back in the cold, the roots may still be viable, depending on how deeply the soil froze. You don’t want to mistakenly pull out a plant that would have recovered once the weather warms.
An exception to this rule is when plants and plant parts turn black and mushy. These can be trimmed immediately.
“They’re not coming back, and they look really ugly,” Webster said.
We talked to Labay and Webster about what homeowners should and should not do to their landscape plants following last week’s historic cold weather. Here’s what they told us.
Bedding plants
The cold decimated many annuals, but not all, according to Webster. Some, such as petunias and begonias, were left limp and flattened in the dirt. These should be pulled.
Others, like hardy pansies, should survive and come back strong, at least until the hot weather arrives in May or June. Still others, including snapdragons and dianthus, may recover, although they probably suffered bloom damage and will need to be deadheaded.
“Except for the plants that are obviously dead, give the rest a few weeks to see if they’ll survive,” Webster said.
None of this counts, he added, for plants that were in outdoor pots, which froze through. “Anything in pots is not salvageable and will have to be replaced,” Webster said.
While popular perennials, such as lantana, salvia, plumbago and shrimp plants, have all died back to the ground, the roots may still be alive. So once warm weather returns, fingers crossed, they’ll grow back.
Even during normal winters, tropical plants like bougainvillea and hibiscus tend to die back to the ground before regrowing from the roots. This year they’re either completely dead or, if they do come back, the regrowth won’t be as strong because the ground got colder, and the cold went deeper, for a longer period of time, according to Labay.
Pride of Barbados, on the other hand, froze back to ground level but will likely return come warm weather. “I’m not anticipating any problems with pride of Barbados,” Webster said.
The good news with many mature plants like philodendrons is that they have an extensive root system. So although the tops may be frozen, they’ll bounce back faster than when they were new.
The bottom line is, you should wait several weeks before cutting anything back. Not only will plants that look dead still be alive, but South Texas has had freezes as late as the end of March. Leaving the branches in place will help insulate the rest of the plant, according to Labay.
Once the threat of a freeze has passed, check the branches to see if they’re truly dead. If they’re still limber and green inside, leave them be. If not, cut them back to about 2 inches above ground level or to the height of the bedding mulch. They should start sending out new shoots soon.
Woody shrubs
Indian hawthorn, flowering quince, wisteria, mountain laurel and other woody perennials will probably come through the cold snap unfazed, although some of the higher branches may be dead. Trim these shrubs according to their normal schedule.
When pruning, cut and inspect the inner tissue. If it’s brown or black, keep cutting until you find green tissue.
Later this summer, look for branches without leaves that are obviously dead. These should be trimmed.
Most roses will have been undamaged by the cold, according to Webster, although it’s unclear how the newly popular Knock Out Rose varieties will fare. “We simply haven’t seen these kinds of temperatures since these roses came out,” he said.
It’s usually recommended that bush roses be pruned around Valentine’s Day, so it’s still not too late, he said. Climbing roses should be pruned after they bloom, usually in May.
Trees
Most native trees, such as live oaks, cedar elms, southern red (Spanish) oaks and Texas ash weathered this winter storm without too much difficulty. But any damage to the interior tissue won’t become apparent for several months — or even years.
“If the internal structures were damaged, we may not see evidence of that until the hot weather arrives and trees have difficulty moving water and nutrients to where they’re needed,” Labay said. “We’ll have to monitor them throughout the summer.”
Signs that a tree is damaged or stressed include it struggling to send out new growth or being more likely to wilt in the heat.
“Be sure to keep trees well watered and fertilized,” Labay said. “But even then some may be too damaged to save.”
Some varieties of palm
trees may not have survived the storm, according to Webster.
“You need to keep an eye on the tops of the palms where the fronds
emerge, usually in the spring,” he said. If that doesn’t happen, the tree is probably dead, and it will eventually have to be taken down for safety reasons.
Popular sago palms may exhibit cosmetic damage over the next week or so, with the spiky green fronds turning brown. “Cut back the fronds, but only the damaged part,” Webster said. “If there’s any green left, leave it. That’s what will help the plant survive.”
Also unknown is how two popular trees — crepe myrtles and Mexican olive — will fare. Both do well during typical winters, but this year certainly hasn’t been typical.
“We had specimens at the Botanical Garden that died to the ground during the 1989 freeze, only to grow back with multiple trunks,” said Labay. “As far as Mexican olive trees, we’re a little north of their typical range, so while it’s still too early to assess, I believe we’re going to see the loss of individual trees.”
Cactus and succulents
Native cactus and succulents generally were able to handle the storm better than nonnatives. The blue agave used to make tequila and popular as a landscape specimen, is native to Mexico, so it likely suffered. But native agaves will probably be fine.
Although prickly pear flopped over in the cold, the native varieties will grow back — although they may need a good pruning. And yuccas, generally a hardy plant, should also be fine, although this year there are no guarantees.
Lawns
There will likely be some lawn damage from the storm, although, again, it may be some time before this becomes fully apparent. “The good news is we had moisture and a blanket of snow to protect turfgrass,” Labay said.
He recommended following the best lawn care practices for each grass species to ensure each lawn gets enough moisture and fertilizer. But even with that, there still may be patches that require resodding or seeding in the spring.
Watering and fertilizing
The storm brought plenty of snow, so the ground is fairly moist. Webster suggests following the typical advice for watering landscapes: water 1 inch whenever the ground is dry to 1 inch below the surface, watering more if it’s very windy or very hot.
Finally, if you haven’t fertilized your entire landscape in the past 60 days, now is the perfect time to do it, according to Webster. He suggested applying organic fertilizer with an NPK (nitrogen, phosphorus, potassium) value of 4-3-2 to the entire landscape as soon as possible. This, he said, will give plants a head start before hot weather arrives.
“Applying fertilizer now is like eating a good breakfast first thing in the morning,” he said. “Especially after the week we just had, it’s better to be proactive in caring for your landscape than to be a procrastinator.”