TREE-PRIMROSE; a genus of the monogynia order, belonging to the octandra class of plants. There are seven species; the most remarkable of which are,

1. The biennis, or common biennial tree-primrose. It hath a long, thick, deeply-striking root; crowned with many large, oval, spear-shaped, plane, spreading leaves; upright, thick, firm, rough, hairy stems, rising three or four feet high; garnished with long, narrow, lanceolate, close-fitting leaves, irregularly; and at all the axillas, from the middle upwards, large bright-yellow flowers.

2. Octovalvis, or octovalved, smooth, biennial tree-primrose, hath upright, firm, somewhat hairy stems, rising a yard high; oblong, spear-shaped, pointed, plane, smooth leaves; and at the axillas large bright-yellow flowers.

3. The fruticosa, or shrubby, narrow-leaved, perennial tree-primrose, hath long thick roots; upright, under-shrubby like red stems, two or three feet high; spear-shaped, lightly-indented leaves; and at the axillas pedunculated clusters of yellow flowers, succeeded by pedicellated, acute-angled capsules.

4. The pumila, or low perennial tree-primrose, hath fibrous roots, crowned with many oval, spear-shaped, close-fitting leaves; slender herbaceous stems 10 or 12 inches long; garnished with spear-shaped, blunt, smooth leaves, having very short foot-stalks; and at the axillas smallish bright-yellow flowers, succeeded by acute-angled capsules.

All these plants flower very profusely in June and July, coming out almost half the length of the stalks from the axillas; and as the stalk advances in stature, new flowers are produced, succeeding those below; in which order the plants continue flowering from about midsummer till October: each flower is moderately large and conspicuous, consisting of four plane petals, which with the calyx forms a very long tube below, and spreading above, generally expand most towards the evening; and are succeeded by plenty of seed in autumn for propagation.

These plants are exotics from America; but are all very hardy, prosper in any common soil and situation, and have been long in the English gardens, especially the three first sorts; but the oenothera biennis is the most commonly known.

The first and second species are biennial, and the third and fourth are perennial in root.

They are proper to be employed as plants of ornament for embellishing the pleasure-garden; they may be placed anywhere, and will effect a very agreeable variety three or four months with their plentiful blow of flowers.

The biennial kinds must be raised annually from seed, for they totally perish after they have flowered. But the perennials, once raised, continue for years by the root.

The propagation of all the sorts is by seed, and the perennials also by parting the roots.