Knautia arvensis (Field Scabious)
|Also known as:||Bluebuttons|
|Habitat:||sun; average to dry disturbed soil; roadsides, fields, open woods, landscapes|
|Bloom season:||June - September|
|Plant height:||1 to 3 feet|
|Wetland Indicator Status:||none|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Numerous tiny flowers in dome-shaped flower heads 1 to 1½ inches across, at the tips of long, wiry, leafless stalks. Flowers are pink to lilac, 4-lobed, the flowers in the outer ring noticeably larger than those in the center of the head and the lobes of unequal size, one usually rather larger than the others. Protruding from the center of each flower are 4 violet-tipped stamens, which give the head a pincushion-like appearance. A short, hairy calyx surrounds each flower. The bracts around the base of the flower head are in 2 layers, leaf-like with long, white hairs around the edges.
Leaves and stems:
Leaves are basal and opposite but usually crowded on the lower stem. The lowest leaves are 3 to 8 inches long, stalked, and may be narrowly lance-elliptic and coarsely toothed, or divided with 3 to 6 narrow, toothless lobes on each side. Leaves are densely hairy and become smaller and stalkless as they ascend the stem.
The flower head becomes a dome-shaped seed head; a hairy, angular seed about ¼ inch long develops below the calyx with the calyx eventually dropping off.
Field Scabious is a garden escapee, introduced from Europe as an ornamental. It is a serious agricultural weed in some areas, noted as particularly aggressive in northwest British Columbia, where it has also been found invading high quality habitat. In Minnesota it hasn't made much of an impact yet, but time will tell. The flower heads somewhat resemble Wild Bergamot (Monarda fistulosa), which has unlobed leaves with serrated edges and flowers are more tubular in shape.
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Photos courtesy Peter M. Dziuk taken on a roadside in Rice County and in a suburban garden in Ramsey County.
Have you seen this plant in Minnesota, or have any other comments about it?