We use seed zones to simplify the description of our seed collections and to aid our customers in purchasing the plants that are most appropriate for their project. Research based, species-specific seed zones don’t exist for most native species, but Level III Ecoregions, which are based on both biotic and abiotic factors, show promise as an approximate delimiter between populations under differing ecological conditions (for more details, see our article on the topic). We use Level III Ecoregions to describe the seed sources for most of the species that we propagate, although any plant that you purchase from us can be traced back to the original collection.
Tree Seed Zones
The biggest exception to our use of Level III Ecoregions is with our native trees. Because of work published in 2002 by the USFS and WA State DNR, most of our native trees do have species-specific seed transfer zones. These research based zones are better guidelines for seed transfer than Level III Ecoregions, and so we use them to describe our seed sources for the species for which they are available.
Despite their usefulness, these seed zones can be a bit confusing. Unlike the old tree seed zones (developed in 1966), the new zone boundaries, zone names and numbers, and elevation bands are different for each species. The maps for species that we routinely grow are displayed below for your reference. If you have questions about these seed zones, please refer to the original publication located at: http://www.dnr.wa.gov/Publications/lm_wfn_seedzone_book.pdf