Description: Introduced hawkweeds generally have a leafless stem, rhizomatous roots, and black hairs along the stem and leaves. Introduced yellow hawkweeds are difficult to distinguish from a number of native hawkweeds so inventory is probably incomplete. This is a concern in the Chilcotin where it may not be distinguished from native yellow Hieracium species.
Habitat and Impacts: The biology of these species is similar to that of orange hawkweed but these species establish more quickly on drier sites. The introduced yellow hawkweeds, like orange hawkweed, are able to spread very rapidly into areas of disturbance. The disturbed soil at the edge of roads and ditch lines are the pathways of spread. Once established this species is able to colonize undisturbed sites.
Method of Spread: Introduced yellow hawkweeds reproduce by seed or vegetatively by stolon or rhizome. Seed production is generally low, but seeds can be produced sexually or asexually without pollination. Seeds are mostly dispersed by animals, people, or vehicles. Although seeds are plumed, they are not spread widely by wind. Seeds can remain viable in the soil for more than 7 years although most germinate within one year of production.
Location: Introduced yellow hawkweeds are currently concentrated in the northern and eastern parts of the Cariboo Chilcotin Coast. Yellow Hawkweeds are expanding aggressively through the Chilcotin, north of Highway 20.
Mechanical: Hand pulling of young plants can be effective but small root fragments can resprout and allow the infestation to persist. Mowing can control seed production, but encourages vegetative growth and spread. Digging plants or otherwise disturbing roots can help spread since new plants can become established from the root, stolon, or rhizome fragments (Wilson and Callihan 1999).
Chemical: Dicamba, picloram, aminopyralid or picloram and 2,4-D are effective at controlling yellow hawkweeds during the spring growing season.
Biological: There is currently no biocontrol agent for the yellow hawkweeds.
CCCIPC Priority and Treatment Strategy: Priority 1 (new invader) in the Chilcotin & Central Coast areas, Priority 2 (containment) in the Central and South Cariboo, and Priority 3 (established) in the Nazko and North Cariboo. A containment area has been drawn for this species (same line as for Orange Hawkweed). All sites of these species outside the hawkweed containment area will be managed in a similar manner as orange hawkweed.
Local Level - hand pulling new and small infestations, chemical for large sites.
Landscape Level - chemical treatments.
Yellow Hawkhead infestation
Yellow Hawkhead plant
Richard Old, XID Serivices, Inc. Bugwood.org
Yellow Hawkhead plant
Invasive species profile taken from the Cariboo Chilcotin Coast Invasive Plant Committee Invasive Plant Regional Strategic Plan
Page last modified: October 30, 2018 09:44:02 PDT