Family: Boraginaceae

Status: Both are declared noxious weeds in Bega Valley Shire (W3, must be prevented from spreading and controlled to the satisfaction of Council) and Eurobodalla (W2, must be continually suppressed and destroyed).

Description:
Both are annual or biennial herbs to about 1m high, which start out as a rosette, elongating to a vertical flowering stem. Paterson’s curse stems are more likely to be widely branching, and viper’s bugloss single-stemmed, but both species may adopt either habit. The blue-purple flowers are large and showy. Viper’s bugloss can be distinguished by the coarse prickly hairs, which make it painful to handle, and the much narrower leaves in the rosette stage. The stem leaves (as opposed to the basal rosette leaves) are heart-shaped at the base in Paterson’s curse, but not in viper’s bugloss.

Preferred habitat and impacts:
Generally found in farming areas in degraded pastures and on roadsides. Both species are more common in inland NSW. Because they are avoided by most stock, they can become dominant in grazed pasture. Paterson’s curse is toxic to pigs and horses, and the hairs of both may irritate cow’s udders. Sheep are more resistant but over a number of years they develop liver damage, which may cause death after sudden stress on the liver as from pregnancy or intake of lush feed.

The flowers are of value to the honey industry.

Dispersal:
Bought-in hay is the usual means of initial introduction, after which the sticky seed is spread in or on livestock, or by water. River beds are a common site of infestation. Seed can remain dormant in the soil for over five years.

Look-alikes:
The trumpet shaped flowers are quite distinctive, but from a distance the purple cover of a dense infestation can be mimicked by purple verbena (Verbena rigida ), another weed with a slightly more reddish-purple flower head.

Control:
Hand chip small infestations. For larger infestations spray with selective or non-selective herbicides, or on high production pastures, cultivate and establish a dense sward of grasses and clovers, which will out-compete the weeds.