Commelina virginica; Commelinaceae (spiderwort family)
The dayflowers are somewhat weedy looking plants, growing maybe 2-3 feet tall, more often sprawling among other plants near river banks and other moist places. They would be easily overlooked but for the spectacular blue color – a rarity among plants. Fewer than ten percent of known species have truly blue blossoms. The individual flowers of Commelina last a single day, but a plant may have a blooming period of a month or more.
There are about a dozen species of Commelina in the US, about half of them native. Much more frequently seen in this area is the exotic C. communis (Asiatic dayflower). It’s easily distinguished from Virginia dayflower by the white lower petal.
Virginia dayflower is found from New York south through Texas and west through Kansas, but it’s extirpated in Pennsylvania. Asiatic dayflower ranges a little further north and northwest.