PYRETHRUM. The pyrethrum or " feverfew " (nat. ord. Compositae), now regarded as a section of the genus Chrysanthemum, flowers in the early summer months, and is remarkable for its neat habit and the great variety of character and colour which it presents. The type form is the Caucasian species P. roseum of botanists, hardy perennial, with finely cut leaves and large flower heads, having a ray of deep rosecoloured ligulate florets surrounding the yellow centre or disk. They bloom during the months of May and June, as well as later, and are always most welcome ornaments for the flower borders, and useful for cutting for decorative purposes. There are now many excellent varieties, both single and double-flowered, in cultivation.
The pyrethrum grows best in soil of a loamy texture ; this should be well manured and deeply trenched up before planting, and should be mulched in the spring by a surface dressing of half -decayed manure. The plants- may be increased by division, the side shoots being taken off early in spring rather than in autumn, with a portion of roots attached. Plants disturbed in autumn frequently die during the winter. They may be placed either in separate beds or in the mixed flower border as may be required. In beds they can be supplemented as the season passes on by the intermixture of later blooming subjects, such as gladioli. Slugs are often destructive to the young shoots, but may be checked by a few sprinklings of soot or lime. Seeds should be sown in spring in a cold frame, and the young plants should be put out into beds when large enough, and should flower the following May. New varieties are being constantly introduced; the reader is referred to the catalogues of nurserymen for named kinds. The powdered root of P. roseum and other species is used in the manufacture of insect powders. P. parthenifolium var. aurem is the " golden-feather " of gardens, so much employed as an edging to flower-beds. P. parthenium, pellitory or " feverfew," was formerly used in medicine. Its double-flowered form is well worth growing. P. uliginosum is the " great ox-eye daisy " that flowers in September and October.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)