Day 8: There are two species of Burdock in Washington state, Arctium lappa (Large Burdock) and Arctium minus (Small Burdock). These plants originated in Europe and Asia where they were cultivated for their edible roots. Both species have become problematic outside their native regions and are considered invasive here. They like nitrogen-rich soils, so I was rather surprised to find two specimens in the forested area where I was hiking yesterday. Since the heads needed to be disposed of in a manner which would prevent the seeds from developing (something which may occur even after a plant has been uprooted), I bagged them and brought them home. This also allowed me to examine the plant so I could determine which species I'd found. Arctium lappa's petioles (the "stem" connecting the leaf to the main stalk) have distinct ridges as shown in the inset; those of A. minus do not. As I've seen on the Nisqually Land Trust's Ohop Valley property, Large Burdock can turn into a ten-foot tall bush. Fortunately, the two specimens I removed were only 12-18" in height, but both had numerous burrs. The trail on which they were found is open to horses, so I am inclined to think that the species was inadvertently introduced to the area by burrs or seeds carried in a hoof or saddle blanket. Many invasives are spread by accident; hikers should always "de-seed" their clothing and boots before entering a new area.
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