Answer: Mild ocean air brings relatively warm winters to your area, but the summer season is often cool and short, with very little heat accumulation. Native woodland plants will thrive, but heat-loving zinnias and calendulas will be hard-pressed to perform except in the hottest spots, such as against a south or west wall, sheltered from cold winds.
With all that said, dogwoods, astilbes, vine maples, ferns and tulips will thrive in your gardening region. For additional suggestions, consult the Sunset Western Garden Book. I find this book to be an exceptional resource, full of cultural information, plant suggestions, and explanations of various growing zones and micro-climates.
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