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Zone Hardiness

Zone hardiness is a USDA ranking having having to do with the average minimum winter temperature.  Zone 1 is where the average minimum winter temperature is below -50 degrees F.  Zone 11 is the area where the minimum winter temperature is above 40 degrees.  Each zone covers a change of 10 degrees F.

In this area we are in zone 7 which is listed as an average minimum winter of zero to 10 degrees.  Each zone is further divided in to sub-zones marked "a" and "b".  Until recently, we were in zone 7a, but we understand that we have been moved up to zone 7b due to the recent warming trend.  Based on the last few winters, we might even make it to zone 8 soon. It is not know at this time how many years the average is taken into consideration before an area's zone is changed.

It is critical that you select plants that are tolerant to the zone we are in.  For example, most citrus trees are only tolerant to zone 8 and would freeze here.

At the other end, some plants need a certain number of hours of temperatures below a certain level.  They need this to go dormant, a requirement for these plants.  A number of berries fall into this category.  

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