By Tamara Galbraith

Ok, hold up a trowel if you know what USDA Hardiness Zone you're in.

As a gardener, knowing your zone is one of the most basic and important pieces of information you can possess. Your hardiness zone tells you what kinds of plants grow well in your area, and when to plant, according to your climate.

Originally developed in 1960, the USDA Hardiness Zone Map divides North America into 11 separate zones. There are also two 'subzones,' labeled "a" and "b" within zones 2 through 10. The map is divided based on the average annual minimum temperature range, by increments of 5 degrees.

For example, the average yearly minimum temp for zone 8a is 10-15° F. The average yearly minimum temp for zone 8b is 15-20° F.

So, when you read a description for a plant that says it grows in Zones 3-8, and you know you're in Zone 7, it is likely the plant will do well in your neck of the woods.

The rules can be bent in either direction. You can create heated "micro-climates" in your landscape (a south-facing sunny site against a brick wall, for example) and artificially raise your zone a whole step. Conversely, warm climate gardeners can put a plant that prefers cooler temps in complete shade, in some cases.

Of course, other cultural and environmental issues contribute to your plants' well-being, so while the USDA Hardiness Zone map is a great tool, it is not foolproof and should be looked at as only a guide. Several U.S. states also have their own hardiness maps, called the Sunset Western Climate Zones, which are much more detailed. The American Horticultural Society also recently came out with a Heat Zone Map, sort of the opposite of the USDA Hardiness Zone map. The Heat Zone Map bases the zones on the average number of days each year that a given region experiences temperatures over 86° F.

Confused by all these zones and maps? Yeah, me too sometimes. But being a good gardener means also being an educated gardener. In addition to your local nursery experts, several sources out on the Web will tell you all you need to know about your area and the plants that do well there.

Web Sources:
USDA Zone Map
Heat Zone Map

Most gardeners have stocked up their garages with all sorts of products to save their plants from natural enemies like hungry insects and overpowering weeds. What many gardeners don't know is this: even more important than defending against enemies is to see that plants get what they need for photosynthesis, especially water. Watering is an art, because under-watering causes water deficiency and over-watering can cause roots to rot.

These problems are easily kept in check with only a few simple steps:

Follow Mother Nature's lead — if you have a desert plant, the soil it lives in may not need watering for days at a time. If the plant is in a fairly moist climate in the wilderness, it will need to be watered more frequently. Avoid being too generous, because the leading cause of plant death is not insects or diseases but simple over-watering.

Get your hands dirty — test the soil with your finger, starting at the top for a moist-climate plant and pushing further in for a plant from a more arid climate. It is recommended to feel most plants about an inch below the surface of the soil. If the soil is moist to the touch but does not wet your finger, the water amount is correct.

Get a can that works — watering cans are especially vital in the care of indoor plants. The best watering can to use is one with a long neck. This is especially important if you have a plant that generates a lot of foliage. The best water to use is tepid water — not too warm or too cool.

Use good soil — sandy soil will let the water rush away, while clay-burdened soil will hold water too long, causing root rot.

Keep your weeds in check — frequent weeding will reduce competition among plants for the moisture in the soil.

Ready your plants for the daytime — water in the morning, to fortify your plants against the hot sun. Using mulch is another good defense. Mulch will keep the soil from taking too much sun and evaporating all the water, as well as helping to keep weeds down.