Terrestrial invasive species

Nature

Most of these invasive plant factsheets are created from the booklet Minnesota invasive non-native terrestrial plants, an identification guide for resource managers.

Check the additional resources and herbicides table for more information.


Orange hawkweed (Hieracium aurantiacum)


 

Description:

Appearance: Perennial herbaceous plant, 10-20" high; each hairy stem bears one or a dense cluster of dandelion-like, orange or yellow flowerheads. The stem grows from a basal rosette of hairy leaves. Hawkweeds colonize and can rapidly dominate a site. They grow well on disturbed, dry low productivity soils.

Leaves: Hairy rosette made up of entire or minutely toothed leaves, spatula-shaped, 4-6" long. They are dark green above and lighter green beneath.

Flowers: Bright yellow or orange dandelion-like, 0.5" to .75" in diameter; arranged in a dense flat-topped cluster of flowers.

Seeds: Each flower bears 12-30 tiny, columnar seeds with a light-brown tuft of bristles for wind dispersal. Seeds and are viable in the soil for up to 7 years.

Roots: Spreads primarily vegetatively through runners, (4-12 per flowering plant), rhizomes, (underground stems producing new plants) and sporadic root buds.

Note: There are two native hawkweeds in Minnesota, which differ from non-native hawkweeds as follows: They do not produce runners, the stems are branched and have few clasping leaves; they do not have basal leaf rosettes, and only the upper stem is hairy; they bear flowers in open elongated clusters.

Ecological Threat:

  • Orange hawkweed is a native of Europe and invades northern moist pastures, forest openings, abandoned fields, clearcuts and roadsides. Its greatest density occurs on newly disturbed sites, as it is an early succession plant. Its largest distribution is in northeastern Minnesota.
  • Loss of native plant diversity in infested areas, orange hawkweed colonizes rapidly forming a solid mat of rosettes. The plant may have allelopathic effects on neighboring plants.

 

Control Methods:

Chemical

Most effective control is with clopyralid or 2,4-D in the rosette stage. A surfactant should be added to the mix to ensure adherence of herbicide to the hairy leaf.

Additional Resources