Galinsoga ciliata (Hairy Galinsoga)

While several of the species we describe on this site are showy, and were grown as ornamentals before becoming escaped invasives, Galinsoga ciliata, the hairy galinsoga, is a small, rather nondescript plant unlikely to attract much attention other than that of botanists.  It belongs to the Asteraceae, the aster, or composite family.  The species is native to Central and South America, but due to human activity has spread far from its original range to become "a cosmopolitan weed", in the words of Gleason and Cronquist (1991). It is an annual plant, and requires recently exposed soil for good establishment, so while it is found in gardens and crop fields, along roadsides, and other disturbed places, it is not particularly invasive of natural plant communities.

Galinsoga ciliata is known to have been growing in the Bartram botanical garden in Philadelphia in 1836, and the earliest recorded naturalized populations in the U.S. were not far from Philadelphia, in Baltimore, eastern Pennsylvania, and New York, suggesting that it may have escaped from there (Shontz and Shontz 1970).  Alternatively, there may have been multiple independent introductions from abroad.  The plant may be spread about by several means—the small, lightweight "seeds" (technically fruits) can be blown short distances by the wind, and are covered with short stiff hairs which help them cling to the fur of animals or the clothing of humans.  They can also be transported in soil.  Early records of the species in the U.S. were concentrated in and around cities, while for a time the plant remained relatively rare in rural areas, suggesting that long distance dispersal was accomplished mostly through the activities of humans, as an inadvertent consequence of travel and commerce (Shontz and Shontz 1970).

In New England, Galinsoga ciliata was at first found in scattered localities.  By 1866 it had arrived in New Hampshire, but the first record of its presence in Massachusetts was not until 1891, by Fernald in Cambridge (Shontz and Shontz 1970).  In 1900 it was seen growing by railroad tracks in Dedham, and its observer noted that it was becoming "more commonly found" (Rich 1900);  in 1908 it was "growing freely" by the Church Street entrance to the subway in Boston (Rich 1908).  As the map below shows, the species is now present in all parts of the state.
 

Animated Images of the Occurrences of Galinsoga Ciliata over Time
(What does this image mean?)

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