What is a Native Plant?
What does "native" mean, in terms of Washington’s plant palette? Members of our Society got together recently and decided on a general definition for Washington State:
"Washington native plants are those species that occur or historically occurred within the state boundaries before European contact based upon the best available scientific and historical documentation."
We wanted to arrive at this definition so that we would agree that we are talking about the same thing, and so we could satisfy ourselves that we are selling native plants at our annual plant sales. This simple definition is used because today we find many plants from other countries which were brought by the recent settlers of this land. Some of these plants will grow only with human care, and do not spread beyond the homes or gardens of their keepers. Others have 'naturalized', they have learned to live and propagate on their own in suitable environments near where they were introduced.
A naturalized species may remain few in numbers and local in distribution, but some of them have become much too successful, covering much ground in city landscapes or in previously natural plant communities, and displacing - crowding out the native species that used to live there. These are the 'invasives', such as Himalayan Blackberry and the common dandelion. These plants often are an eyesore, they invade parks, private home lots, and urban forests. English Ivy creeps up trees and even power poles, where it flowers and produces red berries that are carried by birds to new locations.
Regional Differences
Anyone traveling about our state will realize that different regions are clothed with different types of plant life. These differences are due to differences in rainfall amount and occurrence through the year, temperature regimes and other climate factors such as cloud cover and wind, steepness of the land, the direction that a slope faces, which affects how much sunlight the land receives, and soil types. Many of these proximate factors, or "site characteristics" are controlled in part by the elevation above sea level and whether the land is near the sea coast, on the up-wind or down-wind side of a mountain range.
The most easily recognized regional distinction in our state is between the country west of the Cascade Range, where evergreen forests grow, and the "Eastside", where sagebrush and bunch-grasses predominate. However, you will doubtless recognize a number of sub-regions on either side of the Cascades.