a. and sb. [f. L. bienni-s of two years, bienni-um space of two years (f. bi- two + annus year) + -AL.] A. adj.
1. Existing or lasting for two years; changed every two years.
1621. Howell, Lett., I. I. xli. The Duke is there [at Genoa] but Biennial, being chang’d every two years.
a. 1711. Ken, Hymnotheo, Poet. Wks. 1721, III. 12. Biennial Stores they [ants] treasure under Earth.
1854. Woodward, Mollusca (1856), The land-snails are mostly biennial.
b. esp. of plants; see B.
1691. Ray, Creation, I. (1714), 102 (J.). Then why should some be very long-lived, others only Annual or Biennial.
1755. Gentl. Mag., XXV. 69. The common hemlock is biennial.
1805. Knight, in Phil. Trans., XCV. 262. Annual and biennial plants.
2. Recurring, happening, or taking place once in every two years.
1750. Johnson, Rambl., No. 61, ¶ 6. Whom he condescends to honour with a biennial visit.
B. sb. Bot. A plant that springs from seed and vegetates one year (or growing season), and flowers, fructifies and perishes the next.
1770. Waring, in Phil. Trans., LXI. 385. Biennials … are the natural … product of such places.
1815. Encycl. Brit. (ed. 5), III. 610/1. Of the esculent kinds, the cabbage, savoy, carrot, parsnip, beet, onion, leek, &c., are biennials.
