Know Your Zone

U.S. Zone Map

What is a USDA Hardiness Zone Map and why is it an important tool to any gardener?  The map on the right is a simple breakdown of the current US zones.

The U.S. Department of Agriculture first published the zone map in 1960.  Based on a plants resilience and a zones climate the formulation is not without flaws.  The ever changing weather conditions have required several revisions, most recently just this year.  Still, it is a handy guide to comparing climates and determining what might be the most appropriate time to begin planting.  Example:  I live in the heart of heat and drought where Spring gardening is earlier than other regions.  The winters are also milder which tends to extend the duration of fall gardening.


Each zone is separated by a 10 degree average climate deferential.  In the most recent update the chart holds 26 different planting zones.  The newest addition has done a much more detailed zone calculation than previously.  It is a useful guideline for planting, but continues to often overlook crucial balances.  In the western sphere of the US climates will rapidly vary in the same zone.  Moisture, elevation, soil conditions and animal life will certainly effect the chances of vegetation survival. I am in a very warm climate which is suitable for squash.  I am additionally over run with Grackles, which thrive on my squash blossoms. Visit my blog to see how I addressed the problem. The valley of the Sierra Mountains is much warmer than the upper elevations of the range. This would most likely rank the regions as two separate zones.

Zone charts do not detail the possible consequences of extreme drought or damaging frost on plants.   Snow cover is a protective blanket from hibernating perennials.  Devastating droughts will ruin an entire crop.  How do you realistically determine the expectation of both on an yearly basis? Experience may be the only knowledge that overcomes these challenges.  Zone maps are not predictable tools for current or future climate conditions.  They are generally based on data gathered over a long period of time.  For a more accurate evaluation of possible planting conditions I recommend combining the Zone Map with the Farmers Almanac long range weather predictions.

With all of the missing data and possible draw backs why are zone maps beneficial?  My zone map says I can plant peas and tomatoes in early August.  I know the weather in my location will be too hot to harvest new seedlings as suggested.  Once I know what will produce fall crops I simply wait until the appropriate time for the current temperatures.  Zone maps are beneficial information as long as you utilize them with additional information. 1) Research long range climate conditions. 2) Prepare for possible animal intrusion. 3) Have your soil tested and make adjustments when necessary.  4) Most important make sure you knew the proper needs of your vegetation.  Armed with the proper tools and knowledge you can continue to garden and harvest into the cooler fall months.  Visit this suggest zone planting guide for tips in your particular zone.