We use the USDA hardiness zones which is the standard rating
guide. We are conservative in our
ratings and often with care and attention to siting, many of our plants can be
grown in a colder zone. Our nursery is
firmly in Zone 7. A half hour walk west
to our friend’s garden finds us in an upper Zone 6 as they are
cursed with the mother of all frost pockets – more like a frost crater. A half hour walk east to downtown Port
Townsend and we’re firmly in Zone 8 with some microclimates a balmy Zone
9. It’s maddening.
If you are web searching hardiness zones,
don’t bother with the zipcode method for finding what your zone is – we tried
and it came up with Zone 5 for us instead of the correct Zone 7. We cannot stress enough how
many factors beyond anyone’s control determine the hardiness of a plant. Fertility, age of plant, established or not,
hot or cool summer, soil type, timing of cold, wind, near the drier vent, how
expensive and difficulty of replacement all seem to play a role. Also within any given zone and often within
any given garden, a range of zones and microclimates may be found.
For example, we rate our Crocosmia at Zone 7 but with mulch or dependable
snowcover, these will handle short dips into Zone 6. A few fir boughs placed over a plant or a
temporary wrapping can make all the difference. Remember, plants have feelings too.