Our present garden forms of this genus have originated
from three Mexican species and are among the most
colourful of hardy annuals.
The handsome Cosmos bipinnatus has feathery foliage
divided into linear segments and flowers, rather
like single dahlias, crimson in colour with yellow
centres. Garden varieties vary from white to mauve
and pink, and there is also a double-flowered
form. The plants grow about three feet high.
With rather wider foliage, Cosmos sulphureus reaches
three to four and a half feet, and bears large
yellow, golden-centred flowers.
Cosmos diversifolius is a half-hardy perennial, best
treated as a hardy annual, and bears flowers of
crimson, with red centres on three-feet stems.
It is sometimes listed as Bidens atrosanguinea,
B. dahlioides and Dahlea zimapani.
The seed may be sown under glass in February or
March, and the seedlings planted out in late May.
If desired, it may be sown out-of-doors in late
May for flowering in late summer. All are useful
as cut flowers.
Propagation is from seed.
The flowering season is from July onwards.