Knowing what plant hardiness zone you are in is very important when it comes to gardening. Every type of plant has its own zone, a.k.a. the temperature/climate that it grows the best in.
When you buy a plant, the zone number is usually listed on the tag somewhere. If not, you can always look up online or ask someone what zone the plant is in that you want to buy. Zones let you know what the Plant Hardiness is or, how well that particular plant can tolerate the cold. Basically, you want to make sure you are not going to waste a lot of money by purchasing plants that LOVE warm weather when you live in an area that has very cold winters. The plants will most likely wither away from the cold. If you are dying to harvest your own lemons in the dead of winter and you live in Zone 5, make sure you have a nice sunny, warm cozy spot in your house or in a greenhouse to relocate the plant during the winter months.
Also, interestingly enough, the USDA just modified the plant hardiness zones recently. (Many thanks to http://lostartofsimpleliving.wordpress.com/ for bringing this to my attention)
The change isn’t major but it is enough to make it noteworthy. It seems things are warming up a bit…
So, if you want to see if or how your zone area changed or you never knew what your zone area was, have a look at the map below or go to http://planthardiness.ars.usda.gov/PHZMWeb/ where you can click on the individual states to get a closer look: