HARDY BIENNIALS. Biennials live through one winter period. They require to be sown in the summer months, about June or July, in order to get established before winter; they should be pricked out as soon as large enough, and should have ample space so as to become hardy and stocky. They should be planted in good soil, but not of too stimulating a character. Those that are perfectly hardy are best planted where they are to flower in good time during autumn. This transplanting acts as a kind of check, which is rather beneficial than otherwise. Of those that are liable to suffer injury in winter, as the Brompton and Queen Stocks, a portion should be potted and wintered in cold frames ventilated as freely as the weather will permit.
The number of biennials is not large, but a few very desirable garden plants, such as the following, occur amongst them :
Agrostemma coronaria (Rose Campion): hardy, ij ft., bright rose-purple or rose and white.
Beta Cicla variegata: hardy, 2 ft., beautifully coloured leaves and midribs, crimson, golden, etc.
Campanula Medium (Canterbury Bell) : hardy, 2 ft., blue, white, rose, etc. The double-flowered varieties of various colours are very handsome.
Campanula Medium calycanthema: hardy, 2 ft., blue or white; hose-in-hose flowered.
Catananche coerulea: hardy, 2 to 3 ft., blue or white.
Celsia cretica: hardy, 4 to 5 ft., yellow, with two dark spots near centre; in spikes.
Cheiranthus Cheiri (Wallflower): hardy, ii to 2 ft., red, purple, yellow, etc. ; really a perennial but better as a biennial.
Coreopsis grandiflora: hardy, 2 to 3 ft., bright yellow; the finest member of the genus.
Dianthus barbatus (Sweet William): hardy, I to ii ft., crimson, purple, white or parti-coloured.
Dianthus chinensis (Indian Pink): half-hardy, I ft., various; flower earlier if treated as biennials; must be protected from frost.
Digitalis purpurea (Foxglove) : hardy, 3 to 5 ft., rosy-purple or white; beautifully spotted; the variety called gloxinioides has regular, erect flowers.
Echium pomponium : hardy, 4 ft., rosy-pink.
Hedysarum coronarium (French Honeysuckle) : hardy, 2 to 3 ft., scarlet or white ; fragrant.
Hesperis tristis (Night-scented Rocket) : hardy, 3 ft., dull purplish ; fragrant at night.
Lunaria biennis (Honesty): hardy, 2 to 3 ft., purple; the silvery dissepiment attractive among everlastings.
Matthiola incana (two groups, the Brompton and the Queen stocks): hardy, 2 to 2\ ft., white, red and purple.
Meconopsis. Charming members of the poppy family, of which M. aculeata, purple; M. grandis, purple; M. heterophylla, copperyorange; M. nepalensis, golden yellow; M. integrifolia, yellow; M. simplicifolia, violet purple, are grown with care in sheltered spots, and in rich, very gritty soil.
Michauxia campanuloides, a remarkable bell flower, 3 to 8 ft. high; white tinged purple. Requires rich loam in warm sheltered spots.
Oenolhera biennis and O. Lamarckiana (Evening primrose) : hardy, 5 ft., bright yellow; large.
Scabiosa caucasica: hardy, 3 ft., blue, white.
Silene compacta: half-hardy, 3 to 6 inches, bright pink; clustered as in S. Armeria.
Verbascum Blattaria: hardy, 3 to 4 ft., yellowish, with purple hairs on the filaments; in tall spikes.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)