Plant Invaders of Mid-Atlantic Natural Areas - National Park Service

HERBACEOUS FORBS
Ecological Threat
Once established, if conditions are suitable, Canada thistle can form
dense stands that shade out and displace native plants, changing the
plant community structure and species composition and reducing
biodiversity. It spreads rapidly and is very difficult to remove.
Description and Biology
• Plant: erect, perennial herbaceous plant, to 4 ft. tall with an
extensive creeping rootstock and ridged and hairy stems.
• Leaves: lance-shaped, irregularly lobed, 2-6 in. long with weaklyto
strongly-prickled margins.
• Flowers, fruits and seeds: flowering occurs in late June to
August; flowers are purple to white and about 1 in. long by ½
in. across; seeds are called achenes, are 1-1½ in. long and have a
feathery pappus.
• Spreads: by wind-dispersed seed; expands locally by vegetative
means through lateral roots and root fragments.
• Look-alikes: a number of native and exotic thistle species, some
which are very rare. Numerous species of thistle occur in North
America. Some are invasive, some are native, and most are
dependably difficult to distinguish without assistance.
Prevention and Control
Management of Canada thistle is very difficult and requires repeated
applications of systemic herbicides including products not covered in
this guide. Glyphosate is not very effective against it. Other sources
will likely need to be contacted for more effective herbicides (see
Control Options).
Native Alternatives
After eradicating, plant area with native vegetation appropriate to
site conditions. Refer to References.
Chinese Lespedeza ________________________
Lespedeza cuneata (Dum.-Cours.) G. Don.
Pea family (Fabaceae)
Origin: Eastern Asia
Background
Chinese or Sericea lespedeza was introduced
in the late 1800s by federal and
state agencies for use in bank stabilization,
erosion control, soil improvement,
mine reclamation, forage, hay and other
James H. Miller, USDA FS
purposes. It has been escaping from plantings
for many years and is a well established invasive plant.
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