Facing the freeze: Most plants should've survived this week's Arctic blast

Facing the freeze: Most plants should've survived this week's Arctic blast

January 11th, 2014 by Karen Nazor Hill in Life Entertainment

Kim Bonastia, manager at Signal Mountain Nursery, checks the sprinkler system under a canopy covered with snow and ice.

Photo by Tim Barber /Times Free Press.

A gas heater keeps the greenhouse warm during winter months. Kim Bonastia, manager at Signal Mountain Nursery, checks on the plants daily.

A gas heater keeps the greenhouse warm during...

Photo by Tim Barber /Times Free Press.


• Water the soil thoroughly around plants (except around succulents such as cactus) because wet soil holds heat better than dry, protecting roots.

• Bedsheets, dropcloths, blankets and plastic sheets can be used as covers, but make sure to use stakes to keep the material, especially if it's plastic, from touching foliage. Remove the coverings when temperatures go up the next day.

• For a short periods of cold, say overnight only, low-growing plants can be covered with mulch or straw. Like the material coverings, remove the mulch the next day when temperatures rise.

• Local nurseries should have anti-transpirant sprays to put on foliage to seal in moisture. One application can protect up to three months.

• Cluster container plants close together, preferably in a sheltered spot close to the house, which will hold heat.

Source: University of California

As the "polar vortex" descended on the Chattanooga area (and most of the country), did you worry about the record low temperatures killing the flower bulbs you planted last fall? What about your newly planted trees and shrubs? Concerned that they've been permanently frostbitten? Relax.

Several local gardening professionals say the extreme cold weather will unlikely have a negative effect on bulbs, plants, trees and shrubs, particularly ones that are native to the area. However, the news isn't so reassuring if the plant has come from other parts of the country, especially warmer climates.

"Most plants (in the Chattanooga area) should be in their dormant stage right now, so there won't be as much damage as a spring freeze event, which kills emerging young tissue," says Tom Stebbins, University of Tennessee/Tennessee State University extension agent for Hamilton County.

And "plants native to an area have evolved with special adaptions to help them survive freezing temperatures," even ones as brutal as the 5-degree low on Monday night, he adds.

One such adaptation in native plants is to produce seeds that are dry and won't freeze.

"They come back from seed each year. Many of our perennials are like this," he says.

Others have sap that's essentially antifreeze or mechanisms that pump out water during colder months.

"Having plant sap made of salts and sugars act much like an antifreeze in our cars," he says. "Many have special cells that push water out of the center in the winter and bring it back in the spring - kind of like deflated balloons - to avoid bursting ice crystals."

Flower bulbs, if planted correctly, were not harmed by the cold weather, says Kim Bonastia, manager at Signal Mountain Nursery.

"Hopefully you planted them deep enough and they did not get pushed up from the freezing of the ground," she says. "If that did happen, just try to replant them and hope for the best.

"If the bulb is big (such as a tulip, daffodil, hyacinth), dig the hole about 6 to 8 inches deep; if the bulb is small (crocus, snowdrop, scilla, dwarf iris, muscari, bluebell), dig the hole about 4 to 5 inches deep."

According to the U.S. Department of Agriculture's hardiness map, most of the Chattanooga area falls under zone 7, which means most plants are good down to 5 degrees. Plants that may succumb to the extreme cold may have been left outside in pots or are plants that, while normally OK in zone 7, have not had time to establish a good root system, says Bonastia.

"An established plant has been planted at least two years," she explains. "That is why the plants in your pots might have taken a beating. The roots are not protected from the warmth of the ground."

The trouble is, Stebbins says, "gardeners usually want to push their luck with new plants," using ones that might not be quite as hardy in zone 7.

Local gardens and landOVERSET FOLLOWS:scapes featuring exotic plants from other states and countries may suffer, says Dennis Bishop, curator at the Chattanooga Arboretum and Nature Center.

"Those that naturally grow in warmer climates could suffer minimal to extensive damage or even death after this type of exposure," Bishop says, noting that warmer temperatures later in the week may help lessen any damage.

Still, some plants that are happier in warmer climates can survive if the conditions are right, he says.

"We have palm trees at the University of Tennessee Agriculture Center which have survived many cold years due to their proximity to an old stone building which is radiating some heat," he says.

And don't mistake trees and shrubs losing leaves as a sign of distress, Stebbins says.

"Some can lose their entire above-ground parts but survive from their underground roots and stems" Stebbins says, citing figs as an example.

In the future, gardeners can help their outside plants survive extreme cold temperatures by using a thick layer of bark, pine needles or other mulching material to insulate roots, he says.

Unlike many nurseries, which use heated greenhouses to protect their plants from harsh weather conditions, the majority of the plants, shrubs and trees at the Chattanooga Arboretum are vulnerable to Mother Nature.

"Because we are primarily a natural arboretum with mostly native plants, we expect any damage to be minimal," says Bishop. "Our greatest concern is with the plants in our nursery. Many of them are in containers sitting above ground where they are more susceptible to freeze damage. We will have to wait until spring before we know specifically how much damage was done by the recent cold snap."

As for residential growers, he advises them to stick with native plants "that were made to endure the ups and downs of our climate."

"In the long term, it would likely be best to let the plants go to see what they can do. If they cannot endure this type of cold, I would recommend removing them and replacing them with a hardy native plant alternative."

Contact Karen Nazor Hill at khill@timesfreepress.com or 423-757-6396.