Douglas County Conservation District                                                                         ~Helping People Help the Land~                                                                                                            

by promoting projects through education to further the long- term sustainable   use of natural resources balancing the needs of agriculture and urban growth

                

                                                                            PO Box 688, 7519 E. Hwy 86, Franktown, CO 80116

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Spotted Knapweed
Centaurea maculosa

A biennial or usually short lived perennial with a stout taproot.  It can have one or more stems, branched 1 to 3 feet tall.  Basal leaves up to 6 inches long, blades narrowly elliptic to oblong.  Flowering heads are solitary at the end of branches; bracts are stiff and tipped with a dark comb-like fringe.  The ray flowers are pinkish-purple or (rarely) cream-colored.  Fruits are about 1/8 inch long, tipped with a tuft of persistent bristles.

Rosettes (pictured above) appear in early spring as deeply lobed leaves radiating from a common point.  Herbicides are most effective when applied at this growth stage.

Knapweeds readily establish themselves on any disturbed soil, and their early spring growth makes them competitive for soil moisture and nutrients.  There is some evidence that knapweeds release chemical substances which inhibit surrounding vegetation.  The flowering period extends from June to October.