Good horticulture is the foundation of good bonsai. When growing bonsai it’s important to know what types of trees will thrive where you live. In order to do this you need to know the hardiness zone you live in. Your hardiness zone is determined by the average coldest temperature in your part of the country.
The USDA has just released an updated and interactive Plant Hardiness Zone Map (PHZM). This new map will allow you to search by your zip code or zoom into an specific location to see the variety of zones within that area. The data for this map is…” a result of new, more sophisticated methods for mapping zones between weather stations. These include algorithms that considered for the first time such factors as changes in elevation, nearness to large bodies of water, and position on the terrain, such as valley bottoms and ridge tops. Also, the new map use[s] temperature data from many more stations than did the [previous] map.”
The entire press release can be read here.