bluebuttons, field scabious
(Knautia arvensis (L.) Coult.)

Overview

Appearance

Knautia arvensis is a tall hairy perennial herbaceous plant that grows to about 4 ft (1.3 m) tall. It has a long taproot and tends to form clumps. K. arvensis is native to Europe and temperate Asia. It was introduced for use as an ornamental and has escaped cultivation.

Foliage

The opposite leaves are quite variable. They can be simple or compound with margins entire or serrate.

Flowers

The lilac to purple flowers are held in a dense rounded inflorescence from 0.6-1.6 in (1.5-4 cm) wide. Individual flowers have four lobes, are funnel-shaped and are from 0.4-0.5 in (9-12 mm) long.

Fruit

One plant can produce up to 2000 seeds which may remain viable in the soil for many years. The fruit are four angled hairy achenes from 0.2-0.24 in (5-6 mm) long.

Ecological Threat

K. arvensis infestations establish easily along roadsides, in pastures, fields, meadows and fallow areas. The seeds have an eliosome, which is collected by ants as food, then carried back to their nest. This process aids in the plant's dispersal.

Selected Images

Maps

Invasive Listing Sources

• Alberta Weed Control Act
• Pacific Northwest Exotic Pest Plant Council, 1998
• Wisconsin Noxious Weeds
• Wisconsin's Invasive species rule – NR 40

References