WANTED
DEAD

Russian Knapweed

Leafy Spurge

Hoary Cress

Purple Loosestrife

Canada Thistle

Perennial Sow Thistle

Salt Cedar

SOUTH DAKOTA
STATEWIDE NOXIOUS WEEDS
SOUTH DAKOTA WEED AND PEST CONTROL COMMISSION

 RUSSIAN KNAPWEED: Stems are hairy, tough, branched, and 2 to 3 feet tall. Leaves are grayish
with knaplike hairs. Lower leaves are deeply lobed while upper leaves are short, not lobed, and slender.
Flowers are white or pink to purplish and appear from June - September. Plant origin Eurasia (Europe
and Asia) probably introduced into North America as a crop seed contaminant.
HOARY CRESS: Stems are 1 to 2 feet tall, erect, sparsely hairy, and branched at top. Leaves are
alternate, oblong with a slender base. Upper leaves clasp around stem. Leaf margins wavy and shallowly
toothed. Flowers are small, white, 4 petals, in the shape of a cross and appear April - August. Plant
origin is Eurasia, is very persistent, requires early spring treatment.
PERENNIAL SOW THISTLE: Stems 3 to 7 feet tall, smooth, with milky juice throughout the plant.
Leaves similar to dandelion, irregularly lobed, alternate, 4 to 8 inches long, with spine tipped edges.
Flowers are in branched clusters, bright yellow-orange color, about 1 1/2 inches long. It is important to
distinguish perennial sow thistle from annual sow thistle and prickly lettuce. Prickly lettuce has smaller
flowers with a pale yellow color and leaves are spiny on the midrib beneath. Annual sow thistle does not
have underground creeping root-stocks.
LEAFY SPURGE: Stems are 2 to 3 feet tall, erect branched at top, smooth, and contain a milky sap.
Toxic to cattle but not sheep or goats, sap causes dermatitis in humans. Leaves alternate, hairless, long,
narrow, lower leaves drooping. Flowers are small and green but surrounded by larger, heart shaped,
greenish-yellow bracts, appear May - September. Seed that explodes from three seeded capsules may
remain viable for 5 to 8 years. Origin Eurasia, probably introduced as a ballast contaminant to coastal
New England and as a seed contaminant to western North America.
CANADA THISTLE: Stems 2 to 3 feet tall, grooved, hollow, branched at top. Leaves hairless, spiny,
crinkled margins, smaller leaf than biennial thistle. Flowers numerous on branched heads, about ¾ inch,
lavender, pink, rarely white, appear June - August. Origin is Eurasia and North Africa.
PURPLE LOOSESTRIFE: Stems 8 feet tall, 4 or 6 sided, older plants highly branched. Leaves
opposite, linear, smooth margins, no leaf petiole. Flowers rose-purple, 5 to 6 petals, arranged in long
spikes, appear July - September. This plant grows in wet areas and along waterways. Origin is Eurasia
and Africa.
SALT CEDAR: Stems to 25 feet tall, woody dark brown to reddish-brown. Leaves alternate cedar like
on slender, branched stems. Flowers white to deep pink: 5 petaled: formed in finger-like clusters. Origin
is Eurasia introduced as an ornamental and for bank stabilization. Very invasive especially along
riparian areas.
Our sincere appreciation to the South Dakota Cooperative Extension Service for their help in the
development of this poster.
For assistance contact your local Weed & Pest Supervisor, County Extension Agent, or the South
Dakota Department of Agriculture, 523 East Capital, Foss building, Pierre, SD 57501. Prepared by Ron
Moehring, State Weed & Pest Supervisor.

GOOD NEIGHBORS CONTROL NOXIOUS WEEDS