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Plant Hardiness Zones – What You Need to Know

Gardening Basics

Plant Hardiness Zones – What You Need to Know

By Nina Koziol

Other Factors

The hardiness zone map is a great tool for gardeners, but it’s just a guide. In time, you will have hands-on experience and knowledge about the spots in your garden that warm up first in spring or cool down quickly in fall. Think about those places when you’re buying plants.

Consider that in early autumn, a zone may experience extremely cold weather. This can injure plants even if the temperatures don’t reach the average lowest temperature for your zone. Very warm weather in midwinter followed by a sharp change to more seasonably cold weather can also injure plants.

An 18-foot tall Dawn Redwood tree placed on the west side of our house, quickly leafed out one March when the weather hit 80 degrees and then dropped to freezing the next day. It was not prepared for those conditions and it died. Perhaps if it was planted elsewhere in a protected spot in the garden, it would have survived.

Wrapping the trunks of young trees in fall can help prevent them from cracking during the winter. When in doubt, I’ll wrap smaller shrubs in burlap to protect them from drying winter winds.

Besides hardiness zones, other factors contribute to the success or failure of plants. Wind, soil type, soil moisture, humidity, pollution, snow, and winter sunshine can greatly affect their survival. Where you place a tree or shrub, how you plant it and care for it also influences its survival. Some plants can survive a short period of exposure to cold but longer periods of cold weather may injure or kill them.