Southeastern Wisconsin Invasive Species Consortium, Inc.

SEWISC

Orange Hawkweed

orange-hawkweed-thumb

Scientific Classification: Hieracium aurantiacum L. – Pliny, the Roman naturalist, believed that hawks fed on the plant to strengthen their eyesight and thus it became the Greek and Latin name for this and similar plants, called hawkweed.

Common Names: orange hawkweed, orange paintbrush, red daisy flameweed, devil's weed, grim-the-collier, devil's-paintbrush, fox-andcubs, king-devil, missionary weed

Native Origin: Europe; introduced as an ornamental for desirable flame-colored flowers.

Description: A fibrous rooted perennial herb in the Aster family (Asteraceae) that grows 10-36 inches tall and branching at the top to produce flower heads. Erect stems usually do not have stem leaves, contain a milky juice and are covered with stiff hairs. The simple leaves are basal with 1 or 2 leaves measuring about 4 ½ inches in length. Both leaves and stems are covered with hairs. Conspicuous orange-red ray flowers, bloom June –September with 5 to 35 flower heads. Each flower produces 12-30 tiny seed that are dark brown or black, cylindrical, elongated, longitudinally ridged, barbed and bristled. Seeds can be dispersed by wind, water, or "hitch-hiking", and are often moved in contaminated soil associated with transplanting new plants into gardens and flowerbeds. Seeds remain viable in soil for up to 7 years. The roots are shallow and fibrous with aboveground stolons (that resemble strawberry runners) and below ground rhizomes that allow for aggressive vegetative reproduction. Stolons originate from buds in the rosette when plants flower. These runners radiate out from the original plant and form new rosettes where they touch down and take root.

Habitat: It invades different habitats including urban sites, moist meadows, pasture, hay fields, roadsides, gravel pits, forested areas, tree plantations and riparian areas. Plants prefer full sun or partial shade and soils that are well drained and coarse-textured.

orange-hawkweed-smDistribution: This species is reported from states shaded on Plants Database map. These states reported this species to be invasive: AK, CO, ID, MT, OR, TN, WA, WI, and WY.

Ecological Impacts: Orange hawkweed reproduces and spreads through prolific seed production as well as vegetatively through stolons, and rhizomes. Under ideal conditions, one plant can spread and infest an area 2–3 feet in diameter in its first year of growth. It forms extensive mats that can compete with forest understory plants. It is an aggressive competitor for space, light, and soil nutrients. It has been reported to be allelopathic, producing phytotoxic chemicals in pollen grains that inhibit seed germination, seeding emergence, or regeneration of other plants.

Control and Management: Prevention is the preferred method for control. To prevent spread of existing populations: carefully clean vehicles, boots, clothing, and pets after visiting an infested area.

  • Manual- Mowing reduces seed production, but encourages vegetative spread. Hand pull or dig up small infestations. Dig deeply to remove below ground rhizomes and fibrous roots. Discard or burn plants.
  • Chemical- It can be effectively controlled using any of several readily available general use herbicides such as 2,4-D or dicamba before bloom. Follow label and state requirements.
  • Cultural Control- Treatments such as fertilization can increase the competitive ability of more desirable plants, preventing hawkweeds from becoming established.

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