Washington Planting Zones

Washington has a varied climate east to west. East of the Cascade Range, it has a dry semi-arid climate, whereas western Washington experiences a Mediterranean climate. Continental air masses of Northern America and the Cascade and Olympic Mountains, combined with large semi-permanent low and high pressure systems off the Pacific Ocean contribute to the state’s wildly varying climate and planting zones. Winter can bring a low-pressure cyclone system from the Pacific Ocean, which is responsible for the winds during fall and winter. This pattern brings moist, warm air masses and typically wet seasons. And a high-pressure anticyclone system during spring and summer months brings cool air, wind and fairly dry seasons. Washington’s average annual temperatures range from the Pacific Coast’s 51 degrees to the northeast’s 40 degrees. 

If planning a garden in Washington, first find the hardiness zone you are in. Finding a hardiness zone is easy with Gilmour’s Interactive Planting Zone Map. Hardiness zones, also known as growing or planting zones, are useful in knowing what will grow best in any area. Washington growing zones are wide-ranging and can be anywhere from 4a to 9a, although much of the state falls into the 6a (on the eastern half of the state) to 9a (on the western half) range. Growing zones help gardeners figure out which plants, flowers and vegetables will thrive, which will likely not survive the winters, and when to plant. All hardiness zones, including Washington planting zones, are based on first and last frost dates. Always choose plants rated for the Washington planting zone you are in or lower. For example, if you live in zone 4a, choose plants rated for zones 1 through 4, but not any higher. Plants rated for a higher zone probably will not survive the winter. 

A wide variety of vegetables, plants and flowers grow quite well in Washington. Beans, broccoli, Brussels sprouts, beets, endive, kale, peas, radish, spinach and turnips do well here. Shasta daisies, dahlias, cardinal flowers, primrose, lupine and Solomon’s seal are nice flower options for a Washington flower bed.