Valarianella locusta

This small plant is native throughout Europe where it has been used in salads for centuries. It has escaped cultivation in this country mainly in the Pacific Northwest and Eastern U.S. Other common names include fetticus, milkgrass, Pawnee-lettuce, and white-potherb. The plant is reported to still be cultivated and sold as Mache in some regions.

Corn-salad is usually about 6 to 12 inches high and usually branching. Its stems are square in cross-section, as are many members of the Valerian family. The stems and leaves are rather small but somewhat succulent. The leaves are narrow and attached to the stems in pairs opposite each other. The tiny flowers are in small clusters at the stem tips, with five white petals only about 2 millimeters long that are sometimes tinged slightly bluish.  

Where to find: I have found it a few times when I least expected it, at over 4,000 feet in the Blue Mountains in early summer, and as shown in the photo here last spring near Umatilla Forks Campground along the road. It is an annual plant growing each year from seed, so it is hard to predict where it may show up.