Many gardeners will come across a problem when trying to determine whether or not a plant is suitable for their region. Most plant labels consider a single variable, cold hardiness, and do not take into account other key variables such as heat or moisture. The American Horticultural Society has made a great leap by providing a system for Heat Zones to compliment the well known Hardiness Zones, but there remains to be seen any trend towards using the Heat Zones when indexing plants for nursery sales, and most plant information skips this significant variable.
I have been considering this for a while due to conversations in a popular Facebook Gardening Group after having noticed that areas of Texas and my region of South-Western B.C. share a hardiness zone – yet the overall difference in climates between Texas and B.C. is notable. Relying entirely on Hardiness Zones is clearly not of much advantage considering how many plants will not thrive the same in regions that share only their Hardiness Zone regardless of the “frost resistance” it may or may not have.