Landscape Logic: What’s a hardiness zone?
It’s often said that the key to successful, sustainable plants is putting the right plant in the right place. But first, you need to know your place. That begins by learning your hardiness zone.
The USDA system divides the U.S. into 13 plant hardiness zones — including Alaska, Hawaii and Puerto Rico — based on the average annual extreme minimum temperature of a region. It’s a rough guide to helping gardeners and landscape professionals choose plants that will grow well in their area.
Much of Colorado falls into zones four, five and six, though Colorado’s fruit-growing area near Grand Junction can cross into zone seven.
These numbers should inform your choices when buying seeds or plants for your landscape. You won’t have too much success with a bougainvillea rated for zone 10, so stick to your zone.
Keep in mind that hardiness zone labels can cause some confusion in the Rocky Mountain region. A plant sold as a perennial in a big chain store may grow as a perennial in its home zone, but in Colorado, they would be an annual. Examples include chrysanthemums and verbena.
Don’t forget about other factors. Plant health depends on more than just temperature. Soil quality, sun, wind and drainage can all affect the success of a plant — even if it is labeled for your zone. Keep these variations in mind, and you’ll set yourself and your garden up for success in the growing season.
Of course, consulting with a landscape professional can help you make sense of zones and find the right plants. You can also consider Plant Select at http://www.plantselect.org, which develops plants that often have low water requirements and are well-suited to Colorado’s harsh growing conditions. Any reliable plant source should be able to provide the zone information to help you make your choices.
Cherie Courtade is communication director of the Associated Landscape Contractors of Colorado, of which, Neils Lunceford is a member. Neils Lunceford Inc. can be reached at 970-468-0340 and at http://www.neils lunceford.com.