Helping Landscapes Recover from Extreme Cold

Variegated waxleaf ligustrum isn’t common, but winter damage to woody plants is, after the extreme weather of Winter 2011. Here are some tips Neil has prepared to help you make good decisions.

February 2011

I’ve been working in media horticulture in North Texas for more than 40 years.

As one who answers gardeners’ questions for a career, I’ve been through the ice storm of January 1, 1979.

I’ve been through the prolonged cold spell of December 1983 into January 1984. 292 consecutive hours below freezing. Previous record in our area had been something less than 200.

I’ve been through below-zero temperatures of December 23, 1989.

And now through the spell of early February 2011. As I write this, I’m seeing freezing temperatures over the entire state, clear to the coast and the coastal islands.

Here are my thoughts. I live and garden in a rural part of DFW, so my comments may be gently shaded that way. However, I grew up in College Station, and I’ve worked in all parts of the state, so I’ll try my best to be inclusive. I can’t cover everything, but hopefully I can address most of your concerns here at one time.

Here are my random observations. Some may prove to be accurate this time around. Others may not. A lot of it will depend on where you are and the condition of your plants prior to the cold. These are only offered as one gardener’s experiences. You may have had different, and that’s great. Please don’t spend a lot of time worrying about it.

First general comment: don’t rush to judgment. In many cases, you won’t know the extent of winter freeze injury until plants try to leaf out in the spring. Even if leaves are browned, don’t assume immediately that the plant will not produce new leaves from the old stem tissues. You’ll be better able to tell by early to mid-March, and certainly by April.

Second observation: Texas gardeners have been lulled by 15 years of warm winters into thinking that it was never going to get cold again. We’ve allowed ourselves to become convinced that USDA Hardiness Zones have shifted northward, and that plants we once thought we shouldn’t attempt had suddenly become blessed. You’ll see specific examples below.

Pittosporums: I’ve seen a lot of these planted way north of where they’re adapted. I personally lost my own pittosporums in Farmers Branch (near Dallas) in the 1970s, and I learned how risky they are. If the bark starts to slide off their stems a week or so after the thaw, they’re goners. They do not come back from their roots.

Gardenias: Regular gardenias that were exposed to temperatures of 20 F or below are likely to have freeze damage. They may even have been lost. Dwarf gardenias are even less winter-hardy. Time will tell. If they freeze completely to the ground, they usually do not come back.

Oleanders: Oh, my, these have been planted way too far north. If they faced weather below 20 F where you and they are, they’re probably going to be browned. They probably will freeze back drastically, but they do come back from their roots. However, they won’t flower for a couple of years.

Loquats: These are dependable only as far north as College Station to Austin, and I’ve even seen them freeze in those cities. North of that line, don’t be surprised to see browning, dieback and quite possibly, even loss. They do not come back from their roots.

Figs: The two best varieties of figs for Texas gardens are Celeste and Texas Everbearing. They will probably be hurt by this cold in the northern reaches of their planting regions. If they’re lethargic to leaf out in the spring, or if stems are entirely dead, you may have to prune them back near the ground. They will send up new shoots. They’re grown from cuttings, so what you get back in regrowth will be the same variety you had before. It may be two years before they fruit.

Ligustrums: Waxleaf ligustrums may have brown, indented spots on their leaves a week or two after a severe freeze. That’s indication of freeze damage. They were killed in many parts of Texas in 1983-84. Only time will tell.

Crape myrtles: In our plantings of The Crape Myrtle Trails of McKinney, we’ve seen several varieties hurt by cold over the years. Most types, however, come through just fine. The ones you’ll want to watch, if you’re in a colder part of the state, would include Country Red, Muskogee, Natchez and Sioux, among a few others. If they die to the ground, you’ll get dozens of new sprouts. Retrain them, pruning to remove excess trunks after a year or two. You’ll have lovely "new" plants very quickly.

Cycads (Sago palms): These are winter-hardy only as far north as Houston to San Antonio (maybe protected sites in Austin), yet people persist in planting them outdoors in North Texas, or worse yet, leaving them outdoors in pots. If your sago palm is browned, the merciful thing for you and the plant would be to discard it and find something more winter-hardy.

Palms of various sorts: There are palms that will endure most winters in the southern half of Texas. There are a few that will survive many winters in North Texas. Wait to see if you have new growth out of the tops of your plants. There is no way to judge otherwise.

Pampasgrass: This is a tropical grass that is evergreen many winters, especially in the southern half of the state. In North Texas, however, it will brown in the cold. Use a machete to trim it back. Wear good gloves and long sleeves and long pants. It’s really sharp-edged and wicked. Critical: This pruning must be done before new growth begins in mid-February. Otherwise, you’ll shear off the ends of the leaves, and they’ll be ugly for the rest of the season.

Esperanza: Native to South Texas, the northern half of the state needs to consider this as an annual. It will come back from its roots when it freezes in South Texas. It’s best used as an annual in North Texas.

Firebush: In spite of its name, this is really an annual for most parts of Texas. It often comes back as a perennial in South Texas and in protected locations farther north.

Bougainvilleas: Any freeze at all will harm these. A hard freeze (28 or 29 or colder) will usually kill them. They normally do not come back from their root systems.

Bottlebrush: These are sub-tropical shrubs that can handle light freezes. Normally suited outdoors only as far north as Houston, Corpus Christi and, with some greater risk, Conroe, Brenham and San Antonio.

Asian jasmine: It’s not at all unusual for this plant to brown in hard freezes. Once or twice, in my 40 years of growing it in North Texas, I’ve lost all of the top growth. However, you can mow it back to within 2-3 inches of the soil, and it will send out strong and beautiful new growth come spring. That trim, if needed, should be made in February.

Confederate star jasmine: This is a Zone 8 vine. Some people get it to survive Waco and DFW winters, but most of us aren’t that lucky. Temperatures of 16 or 18 degrees (or warmer) will probably kill it.

Aspidistra: Cast iron plant has one important frailty. It can’t handle extreme cold. I always cover mine in the outskirts of DFW if I hear it’s going to be really cold. Usually, I can prevent winter browning. But, even in extreme cold, when it freezes to the ground, it does send out nice new growth. It’s just slow to regrow, hence my dedication to covering.

Flowering cabbage and kale: The conventional heading varieties of these showy foliar annuals usually turn to mush when they’re exposed to very hard freezes. There’s not much you can do about it, and they usually bolt to flower (end of their road) anyway by March.

Pansies: You’ll know within two days of the thaw whether the plants will come back. These are our most durable winter color plants, but in extreme cold, you’ll certainly lose the flowers. Hopefully, your plants will rebound quickly and start blooming almost immediately. Hopefully you had them covered with frost cloth through the cold. Leave it in place until temperatures rise above freezing.

Posted by Neil Sperry
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