Xanthium strumarium (Cocklebur)

Plant Info
Also known as:
Genus:Xanthium
Family:Asteraceae (Aster)
Life cycle:annual
Origin:native
Status:
  • Weedy
Habitat:sun; disturbed soils; waste areas, roadsides, fields, railroads, along shores
Bloom season:July - September
Plant height:1 to 4 feet
Wetland Indicator Status:GP: FAC MW: FAC NCNE: FAC
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: indistinct Cluster type: raceme Cluster type: spike

[photo of flowers] Tight clusters of green to yellowish flower heads arising from leaf axils in the upper plant, with separate male and female flowers on the same plant. Male flower heads are round, ¼ to ¾ inch across, on short stalks at the tip of the cluster, with 20 or more flowers per head each with a creamy white stamen. Female flower heads are oval-oblong, ¾ to 1½ inches long, stalkless or nearly so, positioned below the males in the same cluster. At the tip of the female head are (usually) 2 flowers: short, cone-shaped projections from which the styles emerge. The rest of the female head is a receptacle covered in stiff bracts, sparsely covered in white hairs and each with a spreading, hooked bur at the tip.

Leaves and stems: Leaf attachment: alternate Leaf attachment: opposite Leaf type: lobed Leaf type: simple

[photo of leaves] Leaves are mostly alternate, sometimes opposite in the lower plant, somewhat variable in size and shape, 1½ to 8 inches long, often nearly as wide, broadly lance to triangular to somewhat heart-shaped in outline, typically with 3 to 5 lobes. Edges are coarsely toothed and/or shallowly lobed and often wavy, surfaces are rough textured, sometimes glandular. Leaf stalks are up to 6 inches long with scattered short, appressed hairs.

[photo of spotted stem] Stems are mostly erect, often much branched, round to weakly angled or ribbed, rough textured from minute hairs, and green to purplish typically with darker purplish spots.

Fruit: Fruit type: barbed Fruit type: capsule/pod

[photo of fruit] The female receptacle persists and hardens into a stiff capsule, turning brown at maturity and persisting through winter. Inside are usually 2 oblong seeds.

Notes:

Cocklebur is a weedy native species and was once considered a noxious weed in Minnesota, but Round-up Ready crops took care of that and most other agricultural pests. It prefers disturbed soils with poor drainage and is most often found in old fields, empty lots, roadsides, construction sites, gravel pits, floodplains and other areas of disturbance. The variability of Cocklebur has given rise to numerous subspecies, varieties and forms, but these are not widely accepted and not recognized in Minnesota. The burred flowers and fruits are distinctive, combined with the large, somewhat triangular leaves and weedy nature make this easy to identify. The fruits somewhat resemble those of Wild Licorice (Glycyrrhiza lepidota), which are only about ½ inch long, more cylindric, and more symmetrically arranged in their clusters.

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More photos

Photos by K. Chayka taken in McLeod and Ramsey counties. Photos courtesy Peter M. Dziuk taken at locations across Minnesota.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Terry S - Minneapolis
on: 2017-06-17 21:23:38

Hi folks, I am working on this species, and read in FNA's genus description that it's the "proximal" 2 - 6 leaves that can be oppositely arranged. Not something I've paid attention to one way or the other, and online images are hard to interpret for this characteristic, but here's one that clearly shows alternate arrangement all the way up the stem: http://www.ufrgs.br/fitoecologia/florars/open_sp.php?img=8364 Terry

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