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Pushing the hardiness limits

Some gardeners are gamblers, trying to grow plants that are known as too tender to grow here. Others gamble by accident, buying and installing plants that are unlikely to survive in their home landscapes, without knowing it.

They often lose.

Ideally, the plants available in our garden centers and nurseries should be marked according to their "Hardiness zones." Labels should also reveal site requirements or special needs.

(A big hint: If you see a plant label with words such as "provide wind protection," "needs Southeast location" or "slightly tender" -- believe it.)

Even to professionals, the Zone and hardiness business is complicated and inexact. We're all still learning as we work with an expanding plant palette.

To increase the odds of buying wisely and increasing plant survival rates, you need this information: Most of Western New York is considered a USDA Hardiness Zone 5, although in some places and conditions even Zone 5 plants die from winter temperatures and weather.

There are also milder parts of WNY that could be considered Zone 6.

Then there are ways for the gamblers and plant people to push the Hardiness limits.

A book by David A. Francko -- "Palms Won't Grow Here and Other Myths: Warm-Climate Plants for Cooler Areas" (Timber Press) -- covers these, making life fun for experimenters.

If you are growing plants you consider fragile, slightly tender, or at risk, try some of these methods. Some aren't do-able now, but I mention them because at least you can add winter protection factors in time:

* When you're deciding what to plant where, look for what Francko calls "heat islands," typically places on the south side and next to the house or against a wall. (They must be well drained too.) These spots are a micro-climate that's the equivalent of a Zone 6.

* Measure exactly how much warmer this location is, by putting a thermometer 1 or 2 feet above the ground and reading it just before the sun comes up (the coldest time of day). Compare it to another thermometer at the same height in more exposed parts of the yard. Five or 10 degrees of difference may mean survival or death.

* Plant vulnerable plants early in the growing season, rather than at the last-minute (with proper TLC, of course).

* Provide winter protection with a burlap wrap, Shrub Coat or even a blanket or cardboard during the coldest periods.

* Mulch deeply around plants at risk -- even 6 to 12 inches -- after the ground has frozen. (Remove in spring.)

* Water your plants well (especially evergreens) until the ground freezes, and if there is a winter thaw, do it again.

* Don't prune in fall or early winter; wait until late winter or early spring.

Or if this sounds like way too much trouble, buy plants that we know can take the occasional minus 20, big winds and radical temperature changes. That's Zone 5!

Sally Cunningham is a garden writer, lecturer and consultant.

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