Rough Cocklebur

Xanthium strumarium

''Xanthium strumarium'' is a species of annual plants belonging to the Asteraceae family. It probably originates in North America and has been extensively naturalized elsewhere.
Cocklebur or Xanthium strumarium 1.75x, f6.3, EAf17.3, 1/20sec, ISO100, 172 micron per step, 69 steps_2024-05-26-06.52.27 ZS PMax Geotagged,Rough Cocklebur,United States,Xanthium strumarium

Behavior

The species is monoecious, with the flowers borne in separate unisexual heads: staminate heads situated above the pistillate heads in the inflorescence. The pistillate heads consist of two pistillate flowers surrounded by a spiny involucre. Upon fruiting, these two flowers ripen into two brown to black achenes and they are completely enveloped by the involucre, which becomes a bur. The bur, being buoyant, easily disperses in the water for plants growing along waterways. However, the bur, with its hooked projections, is obviously adapted to dispersal via mammals by becoming entangled in their hair. Once dispersed and deposited on the ground, typically one of the seeds germinates and the plants grows out of the bur.
Rough Cocklebur (Xanthium strumarium) Achene Growing at a disturbed forest edge. 

This "bur", with its hooked projections, was adapted for seed dispersal in mammalian fur. They easily cling to human clothing as well (as evidenced above)!

Note: Our dog Snorri has a bad habit of getting into these plants, and it is a tedious process to dig them out of his long fur! Fall,Geotagged,Rough Cocklebur,United States,Xanthium strumarium

Reproduction

The species is monoecious, with the flowers borne in separate unisexual heads: staminate heads situated above the pistillate heads in the inflorescence. The pistillate heads consist of two pistillate flowers surrounded by a spiny involucre. Upon fruiting, these two flowers ripen into two brown to black achenes and they are completely enveloped by the involucre, which becomes a bur. The bur, being buoyant, easily disperses in the water for plants growing along waterways. However, the bur, with its hooked projections, is obviously adapted to dispersal via mammals by becoming entangled in their hair. Once dispersed and deposited on the ground, typically one of the seeds germinates and the plants grows out of the bur.

References:

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Taxonomy
KingdomPlantae
DivisionAngiosperms
ClassEudicots
OrderAsterales
FamilyAsteraceae
GenusXanthium
SpeciesXanthium strumarium