Walk around the edges of your yard and you might see it. Dayflower is that grass-like weed with the little blue flowers. It finds its way into our flowerbeds and goes unnoticed, hiding itself under the cover of larger plants until those two big blue petals jump out at us. There is also a small white petal that often goes unnoticed. Each flower only lasts for one day.

Originally introduced from Asia, common dayflower looks a little like a green Wandering Jew. It has short leaves two or three inches long on creeping stems. Leaves clasp the stems and often hair-like tissue resides in this area. When stems contact the ground roots form profusely where leaves emerge from the stems.

Plants rarely grow much more than two feet tall. That’s one reason it often remains somewhat camouflaged.  Deer-tongue grass is another species some confuse with it when plants are young, but once the blue flowers emerge identification is simple.

Dayflower is a hardy annual or tender perennial, meaning that controlling it is usually predicated on keeping it from going to seed. Quite often parent plants don’t survive substantial winters unlike its cultivated more compact cousin, widow’s tears. Dayflower grows well in wet shady areas or sunny places, especially if shrubs or other plants are present.

Dayflower looks harmless and delicate, but it can be an invasive weed. Few chemicals are effective against it either, and none that I’m aware can be purchased without a pesticide license. Unless plants are very young, Round-up isn’t effective within recommended rates even with multiple applications. Treatments with it merely endanger your desired plants. Hand weeding is your only decent option.

Don’t discard those invasive devils. The leaves are edible and mild tasting. I like them better lightly cooked with butter and salt, but they can be used in salads. They don’t get strong as the season progresses, but the stems become tough, so discard them. Leaves are oxalate accumulators, so don’t eat too many and be sure to cook them if you form kidney stones. I hear the seeds are edible, the flowers too, but I’ve never fooled with them.

The flowers can be used to make a bright blue ink. The blue colorant in the dye is a chemical called commelinin, interesting since the genus name of dayflower is Commelina. This dye, extracted extensively in Japan, fades when exposed to prolonged sunlight.

Dayflower is prescribed medicinally by herbalists to treat sore throats and tonsillitis. Since it is a diuretic it has been used to treat urinary ailments. Plant sap has styptic properties similar to those of plantains, yarrow and other wild herbs. Extracts also show antibacterial activity.

Research is presently being conducted on the use of dayflower extracts to treat type-2 diabetes. These plants contain alpha-Glucosidase inhibitors, which interfere with the breakdown of complex carbohydrates and formation of sugars. In short, they slow down starches from turning to sugars and keep too much blood sugar from entering the bloodstream. This could also help with obesity problems. Research is in its infancy, but it has potential.

Thick stand of dayflower

close-up of flower

another flower close-up

close-up of foliage

Ted Manzer teaches agriculture at Northeastern High School.