This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Introduced. Perennial. Propagates by seeds and by stolons.
Time of bloom: May to July.
Seed-time: June to August.
Range: Eastern Canada and New England to southern New York.
Habitat: Fields and waste places.
This plant is a member of the Mint Family which have in common the characteristics of square stems, opposite leaves, corollas more or less two-lipped, stamens four in unequal pairs or sometimes only two, and a deeply four-lobed ovary, which in fruit forms four tiny nutlets or achenes surrounding the base of a single style in the bottom of a persistent calyx. (Fig. 239.)
Stems rather stout, smooth or only slightly hairy, six inches to a foot in height. Root-leaves tufted, obovate, rounded at apex, scallop-toothed, tapering to margined petioles; stem-leaves sessile or nearly so, rounded or a short oval, becoming entire near the top. Thrust out from the tufted basal leaves are numerous slender stolons, a foot or more long, which take root and form new plants, causing the weed to grow in patches. Flowers, pale blue or white, in axillary clusters, sessile, very small; the upper lip of the corolla very short and cleft, the lower one three-lobed and spreading; calyx five-toothed. Nutlets roughened, and very small.
Scattered colonies of the plant should be hoed out and removed from the soil, for if left on moist ground it will take root again. Cultivation of the soil destroys the weed, and badly infested ground should be so treated.
 
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