Field scabious

(Knautia arvense)

Erect perennial up to 1.5 meters (4 feet) tall.  Introduced from Eurasia as an ornamental. Also known as bluebuttons.

Quick Identification:

• Solitary violet flower heads.
• Ring of narrow, green floral bracts.
• Leaves deeply lobed into 5 to 15 narrow segments.
• Lower part of plant is bristly and hairy.
• Distinctive V shaped branching pattern on main
stem.

Interesting Facts:

Still sold as an ornamental and butterfly attractant. Potential impacts to riparian areas by excluding native plants.

Management:

Hand pulling or digging is effective if entire root is removed. Best done when soil is moist. Wear gloves, avoid skin contact.  If any portion of flower is beginning to emerge, or if seed heads are formed, pick, bag, and remove. Selective herbicides are effective.

Reproduction and Dispersal:

By seed. Most seeds fall close to parent plant but animals also facilitate seed dispersal in their manure.

Habitat Preference:

Roadsides, pastures and fields. Prefers nutrient-rich and moderately moist to dry loam soils, but also establishes in gravelly soils. Can invade undisturbed plant communities.

Flowers:

Violet blue to pale purple, up to 4 cm wide; solitary on the end of a long, leafless stalk.  Below each flower head are 8 to 12 sepals and a ring of narrow green bracts. Florets have 4 to 5 lobed petal tubes, four stamens, and a single pistil.

Leaves and Stems:

Low growing rosette in first year. Rosette leaves are highly variable and could have smooth edges or can be deeply lobed. Stalked leaves are 10 to 25 cm long.  Produces one main stem the second year. Stem leaves are opposite, stalkless and deeply lobed into 5 to 15 narrow segments.

Seeds:

Rectangular, light brown, four-sided seeds that are densely covered with long hairs.  Can produce 200,000 seeds and may remain viable in the soil for several years.

Roots:

Woody taproot, often with branches.

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Field scabious flower heads