_Dianthus._--Chiefly rock plants with handsome and fragrant flowers, the smaller sorts growing in light sandy soil, and the larger border plants in rich garden earth. Of the dwarfer sorts for rock gardens, _D. alpinus_, _D. caesius_, _D. deltoides_, _D. dentosus_, _D. neglectus_, _D. petraeus_, and _D. glacialis_ are good examples; while for borders or larger rockwork _D. plumarius_, _D. superbus_, _D. Fischeri_, _D. cruentus_, and the clove section of _D. Caryophyllus_ are most desirable.
_Dicentra._--Very elegant plants, of easy growth in good soil. _D. spectabilis_, 2 to 3 ft., has paeony-like foliage, and gracefully drooping spikes of heart-shaped pink flowers, about May, but it should have a sheltered place, as it suffers from spring frosts and winds; _D. formosa_ and _D. eximia_, 1 ft., are also pretty rosy-flowered species.
_Dictamnus._--_D. Fraxinella_ is a very characteristic and attractive plant, 2 to 3 ft., with bold pinnate leaves, and tall racemes of irregular-shaped purple or white flowers. It is everywhere glandular, and strongly scented.
_Digitalis._--Stately erect-growing plants, with long racemes of pouch-shaped drooping flowers. The native D. purpurea, or foxglove, 3 to 5 ft., with its dense racemes of purple flowers, spotted inside, is very showy, but is surpassed by the garden varieties that have been raised. It is really a biennial, but grows itself so freely as to become perennial in the garden. An erect flowered form is called _gloxinioides_. The yellow-flowered _D. lutea_ and _D. grandiflora_ are less showy. Good garden soil, and frequent renewal from seeds.
_Doronicum._--Showy composites of free growth in ordinary soil. _D. caucasicum_ and _D. austriacum_, 1 to 1½ ft., both yellow-flowered, bloom in spring and early summer. _D. plantagineum excelsum_, 3 to 5 ft. high, is the best garden plant.
_Draba._--Good rockwork cruciferous plants. _D. alpina_, _D. aizoides_, _D. ciliaris_, _D. Aizoon_, and _D. cuspidata_ bear yellow flowers in early spring; _D. cinerea_ and _D. ciliata_ have white flowers. Gritty well-drained soil.
_Dracocephalum._--Handsome labiate plants, requiring a warm and well-drained soil. _D. argunense_, 1½ ft., _D. austriacum_, 1 ft., _D. grandiflorum_, 1 ft., and _D. Ruyschianum_, 1½ ft., with its var. japonicum, all produce showy blue flowers during the summer months.