|Have any seed growers changed the Pacific Northwest from growing Zone 5 to another zone designation? I had heard that two seed growers had done so based on "climate changes", but am more than a little skeptical.
|The USDA puts the Pacific Northwest in gardening zone 8. Sunset Western Garden book has placed the PNW in zone 5. The zones are guidelines only, because each yard contains microclimates unique to the area. I like the term "your mileage may vary".As far as selecting woody perennials, shrubs and trees, you don't need to know the zone designation as much as you need to know the average low temperatures and the average frost dates for your immediate area. If a plant is hardy to a zone with a lower number than your zone, it will survive in your area. If a plant is hardy to a higher zone number, it may struggle to live in your yard. There are no absolutes in the gardening world. To be on the safe side, grow only plants that you've observed to reach maturity in your area. Arboretums and botanical gardens are good places to visit for ideas.
Hope the information is helpful.