Russian Knapweed
Family Asteraceae
Acroptilon pepens L.
Designation/Status
Arizona
Noxious Weed List - Prohibited
Federal Noxious Weed List – Not Listed
Origins
Russian Knapweed originates in regions of Europe and Asia.
Plant Characteristics
Life Cycle: Creeping perennial forming
dense colonies as a result of buds from its black, spreading,
adventitious roots (up to 25 feet deep). Flowers are commonly
found from June to September. Seeds can lie dormant for up to five
years after being shed. Each plant can produce up to 1200 seeds,
though primary mode of plant spreading is by the adventitious root
system the plant develops.
Visual Appearance: Stems are erect,
openly branched and can reach a height of 4 feet tall. Lower
leaves range from entire to lobed, sometimes having serrated edges
on upper leave margins. Upper leaves are smaller, entire, and
attached directly to the stem. Stems are covered with fine, white
hairs that give the stem a blue-green color . Cone-shaped, pink to
lavender flower heads are borne at the end of leafy branches.
Flowers are 0.25 to 0.5 inches in diameter. Floral bracts are
greenish, smooth, and papery with a rounded or pointed margin.
Seeds develop in late summer, being oblong shaped, and gray -
brown in color. The seeds are covered with many fine, white hairs
with a ring of bristles on the apex of the seed.
Habitat
Establishes in cultivated fields, orchards, along
stream banks and roadsides. Frequently occurs in areas that have
shallow water tables or have extra water from irrigation.
Control
Measures
Mechanical and Cultural: As a stand alone
treatment it is almost useless, as Russian Knapweed has a complex
system of adventitious roots that cause the plant to re sprout.
Best method of control is to chemically or mechanically remove the
above ground portion of the plant, then introduce competitive
plant species to replace the bare ground once occupied by the
weed.
Biological: None
Chemical: Best chemical control has been with a mixture
of 2,4 -D plus Picloram.
Other Points of Interest
Brought to America
in 1898
