Capitalize Zone or Zones when referring to the climate regions used primarily in gardening contexts.
a Zone 4 garden site
The plant is hardy in Zones 4–8.
Check with a nursery for cultivars suitable for your Zone.
Some plants are unsuitable for colder Zones.
Also see the garden style section of SIMStylebook.com.
Capitalization
Acronyms
After colons
Company names
Directions and regions
Generic terms
Headlines
Job titles
Product names
Websites
Zones