Fields of Cosmos bipinnatus, or Mexican aster, were a relatively common sight during my recent visit to Mexico. Admittedly, few localities were as dense as this patch growing amongst a corn crop (where it was readily apparent that no corn would be harvested this season).
Many gardeners simply call this species cosmos. It has long been a cultivated ornamental, with several cultivars having received Award of Garden Merit designations from the Royal Horticultural Society. Unlike most annual species that offer showy displays but are low-growing, Cosmos bipinnatus can exceed 1.2m (4 ft.) in height. These particular plants were in the 1 to 1.2m range.
Cosmos bipinnatus is native to this area of central Mexico, but, because of its popularity in gardens (and subsequent escaping from), it can now be found naturalized in similar open, disturbed habitats on most continents.
An excellent account of this species in cultivation is available from Botany Boy’s Plant Encyclopedia: Cosmos bipinnatus.
As an aside, apologies for the shortage of entries lately–I have just (mostly) recovered from a cold. Dominic has been very busy, and a number of his entries will soon make an appearance!