Bird's-foot Trefoil

When I pulled over and got out to take a photo along the Wildcat Hills Rd, NW of Calgary, I was surprised to discover that the yellow flowers in this field were not Canola, but Bird's-foot Trefoil. I don't often see this plant, but it is a weed here in Alberta. It is grown as a crop and has spread to various places. Introduced from Eurasia, it can be found (if you know where to look) growing along roadsides and on waste areas. I think I've only ever seen it in about five or six places, though. It blooms from June to September. The plant was named for the arrangement of the long, narrow seedpods/legumes, which resemble a bird's foot.

en.wikipedia.org/wiki/Lotus_corniculatus