Understanding Climate Zones

Front Garden - Understanding Climate Zones
Understanding Climate Zones is important to gardeners . That way you know what kind of plants to put in your garden. There are several different climate zone systems in use. I will talk about the ones used in the United States but there are others other climate zone systems in use in Australia, Europe and in Canada.

The climate zone system I am most familiar with, is the USDA hardiness zone system. The USDA breaks down the United States and southern Canada into 11 climate zones. This takes into consideration the average lowest temperatures in that area. There are several interactive USDA zip code analyzers where you can input your zip code and it will give you what what hardiness zone you live. For instance I live in zone 7b or 8a a depending on which source I look at.

Another system is the Sunset Hardiness Zone system. This divides the 13 Western states into 24 different hardiness zones. This system is a little more accurate than the USDA system and gives a little more detail. Sunset Magazine has a website with a description of all of the different zones. I could not find an interactive zip code map. However, the website does give the details on each zone with cities that fall into those areas. That way you can tell what zone your city falls in. Looking at the Sunset map, I can see that I am in Sunset Zone 6, here in the Willamette Valley.

The American Horticultural Society provides a Heat Zone Map, with zones showing how many days your area has temperatures above 86°. This is the temperature at which many plants begin to show some heat stress. The Heat Zone Map is a nice complement to the cold hardiness maps that are put out by the USDA and Sunset Magazine, because you now have an upper temperature limit for which a plant will survive in your area . The American Horticultural Society Heat Zone Map site has an interactive ZIP code analyzer which shows you how to determine what heat zone you live in. I input my own zip code, and discovered that I live in zone 4 or 5. This means that I have approximately anywhere between 14 and 45 days that are over 86° in my area. This is pretty consistent with my own observations of the climate conditions in my area. On the same web page you can also read more information about the map and also purchase your own copy of the map.

I found some additional very fascinating information on on climate zones on www.Plantmaps.com They provides an interactive map in which you can enter your zip code. It will give you not only the USDA zone for your area but it will also give you the number of days over 86°. (those readings gave slightly different results than the AHS map, and didn’t seem quite what i have observed in my two years living in this area) It will also give you the first and last frost dates, and it will give you a list of the different eco-regions in your state. The eco regions show naturally occurring geologic and native plants for that region. On another link on that website you can also find native trees in your region.

I think that you can say that there is quite a range of different climate zone systems. Using a combination of one or more of them you should be able to determine what kinds of plants will do well in your home garden. I do know that a lot of plant tags in your nursery will state what climate zones the plant you want is suitable for.