Zones may be the most misunderstood terms in all of gardening and, yet, can be the reason your garden is successful or not.
There are two parts to zone ratings and they need to work
together to insure your plant will have a chance to grow year after year.
The first part is the zone you garden in. These zones range in
values from zone 2 which is minus 40 to zone 11 which is 40. The only
information your zone gives you is this winter time temperature rating. It
does not address summer heat, summer humidity, the soil in your area or any
other numerous conditions that may exist where you garden. For instance, we
are a zone 8 but have very dry summers while Georgia might also be a zone 8
but have very humid summers. Same zone but different growing challenges.
The second part is the zone given to the plant. Again, this number only relates to the winter time minimum temperature a plant can survive once it is established. Most plants take about a month to become established in spring and summer and can take longer as fall approaches.
It is important to note that zone ratings for plants are based on plants grown in the ground and not in containers. The ground provides an insulating value not found in containers.