Understanding Zones

Learning where you plant prefers to live

Most catalogs and plant tags will give you a range of growth for a plant divided into zones. Sometimes things can get confusing because there are many different systems of zone classification, and it's not always clear which zones are being referred to.

The US Department of Agriculture has a map that divides the US into 11 zones based on the average low temperature in each area. Usually if the zone type is not mentioned, it's the USDA zones that are being used - they've been a standard in the plant world for many years.

What USDA climate zones don't tell you is how hot the plant can stand to be, and as a result, neither do most plant tags. Strange as it may seem, some plants like cool weather and literally curl up and die if they get too warm.

To take the warmer conditions into account, the American Horticultural Society developed a Heat Zone map that will tell you the average number of days, in your area, during which the temperature gets so hot it can stress plants.

Ok, so we've covered cold, we've covered hot... what else is there? Actually, lots of things. So the folks at Sunset developed a set of zones that break the country up into roughly 45 climate zones based on similar rainfall, temperature, length of growing season, and several other climate factors. Usually if you see a zone number larger than 11, you can be pretty sure it's a Sunset zone.

So what do all of these zones mean for you and your plants? Well, if you can find out what zones you live in, and what zones different plants prefer - it can make it easier to find plants that will work for you. Luckily, gardening in containers gives you the ability to control your plant's environment a bit more than you can with traditional backyard gardening. Move a plant indoors in winter if it's not hardy enough to survive outdoors where you live. Build a shade for plants that don't like to be too hot. So keep the zones in mind, but don't let them take over your life. It's your garden, after-all.