You never really know how cold it's going to get in North Texas. The first 10 years of the decade weren't all too bad. Then we hit those cold and icy spells last winter. Already we're tasting much the same type of experience, as temperatures drop heading into the winter. Since weather has played such an important part of our gardening lives in 2011, let's assess where we are and where we may need to go.
We'll start with the basics. Are our plants sufficiently "hardened"? That is, has the transition from fall into winter been gradual enough that our plants could adjust? In most cases, yes. Our hope always is that they'll be exposed to a few nights of 50s, then 40s, then 30s before they're plunged into the 20s and teens. We should be fine there.
However, no one really knows what impact this past summer's drought is going to have on plants, should we have unusually cold weather this winter. Plants are certainly going into the winter in weaker conditions than we've ever seen before, so they may need a little more special attention than usual. In short, probably the most beneficial thing you can do for distressed plants now is to water them deeply and thoroughly prior to expected extreme cold. Dry plants are always hurt more than those that are properly hydrated.
You need to know each plant's (primarily shrubs, vines and ground covers) hardiness zone. That's the ranking done through the exhaustive research of the United States National Arboretum decades ago. It catalogued every county in America and recorded the average lowest temperature reached in each of those counties. North Central Texas bridges between Zones 7 and 8. Zone 7 can expect temperatures into the single digits at least once each winter. Zone 8 can expect temperatures only into the teens.
It's always best to use plants hardy to your zone or to the next colder one. For example, people in Zone 7 would want to choose mainly from plants rated for Zones 7 and 6. All of this will be clearer if you do a Web search for "United States National Arboretum Plant Hardiness Zone map," then click through to see your specific county or region.
Put the Hardiness Zone map to use by knowing each and every plant that you're growing. Look them all up online or in gardening references, and record their zones, plant by plant. Keep the list handy, and you'll always know which plants, if any, will need to be given special care or covering during a particular cold spell. It pays to keep your eye on the five- or 10-day forecast. It also pays to have the necessary supplies easily available in your garage or tool shed.
Lightweight fabric products, often called frost cloths, are the quickest and most successful way to add 6 or 8 degrees of protection to your tender plants. They're feather-light, and they can easily be laid over shrubs, ground covers and annuals. Weight them to the ground securely to prevent strong winter winds from lifting them up or carrying them away. Bricks or river rock work well, or you can physically secure the fabrics to stakes.
Container plants give up about 20 degrees (two hardiness zones) compared with their in-ground cousins. That's because their root balls are totally exposed. That soil will freeze when it's extremely cold, while our garden soils normally don't freeze more than a couple of inches deep in the coldest of winters.
Mulching is another valuable option on your list of winter-survival tricks. Mulches don't really "keep the soil warm," as many will hint. In reality, they moderate the rates at which the soils freeze and thaw. That lessens the damage done by cold (or heat). It's basically the same principle that tells us to thaw our frozen hands gradually, not in a stream of hot water. Mulching also retards weed growth and reduces the soil-to-air contact, slowing the evaporation from the soil's surface.
Quick tips on related topics
Irrigation: If you don't have a "smart controller," put your sprinkler system into the "manual" mode so that you can determine when it runs. It will only take a flick of the button, and your system will do its job. In the meantime, you'll be saving water at a critical time.
Garden pots, statuary, etc.: Some of these are made from cold-sensitive materials. Gazing balls can break in extreme cold. Clay pots can craze or crack. Fountain and pool pumps can freeze. Talk to water gardening experts for details on how best to handle each situation. They'll have necessary freeze guards and other winter maintenance products.
Neil Sperry publishes Gardens magazine and hosts Texas Gardening noon-1 p.m. Saturdays and 9 a.m.-noon Sundays on WBAP AM/FM. Reach him during those hours at 800-288-9227 or 214-787-1820.