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Invasive Species of the Month: August 2012

Orange hawkweed (Hieracium aurantiacum)


Also Known As

Devil's weed, devil's paintbrush, orange paintbrush, missionary weed

General Description

Orange hawkweed is a perennial herb that is native to Europe. It can form dense mats that displace the native forage species that wildlife depend on for food. It shares many characteristics with meadow hawkweed (Hieracium caespitosum) but can be distinguished by its orange flowers. Orange hawkweed reproduces by seeds, roots, and rapidly spreading above ground runners.

Growth Habit

Orange hawkweed usually grows 4–24 inches tall and forms a cluster of flowers at the top of the stem. Its long, leafless stems are densely covered in bristly, black hairs. When broken, the stems and leaves exude a milky juice.

Leaves

Narrow, alternate leaves grow in a rosette at the base of the plant. Leaves are lanceolate to club-shaped, 1.5–8 inches long, and covered with long, soft hairs. 1–3 small, clasping leaves may be present on the lower half of the stem.

Flowers

Small, reddish-orange flowers have square-edged petals, and usually appear from June to September. Flowers occur in a compact cluster of 5–30 at the top of the hairy stem.

Seeds and Fruit

Seeds are tiny and purplish-black, with white plumes attached to the flattened ends.

Habitat

Orange hawkweed thrives in meadows, pastures, open forests, rangelands, and other disturbed areas but can also be found along roadsides and in gardens and gravel pits. It thrives in full sun and does not tolerate heavy shade.


Additional Resources

Species Identification and Characteristics
Alberta Invasive Plants Council Fact Sheet (PDF)
Colorado Department of Agriculture Fact Sheet (PDF)
Invasive.org Images and Overview
Montana Weed Control Association Fact Sheet
WeedsBC Fact Sheet (PDF)

Management and Control Resources

Ecology and Management of Invasive Hawkweeds: Montana Department of Agriculture (PDF)
Orange Hawkweed and Meadow Hawkweed Complex: Montana State University Extension (PDF)
USDA Forest Service Species Information

 

Past "Invasive Species of the Month" Profiles