An evergreen shrub of remarkably quick and luxuriant growth, becoming 6 to 9 ft high, and nearly as much through, in three or four years when planted in rich soil. Branchlets round, semi-woody, covered with silky hairs. Leaves alternate, digitate, with seven to eleven (usually nine) grey-green leaflets; each 3⁄4 to 2 in. long, varying in size according to the vigour of the plant; they are oblanceolate, pointed, downy beneath, the common leaf-stalk rather longer than the leaflets. Flowers in erect, terminal racemes 6 to 10 in. long, fragrant, sulphur-yellow in the type and in most wild plants, but occasionally blue or purplish. Seed-pods 11⁄2 to 3 in. long, 1⁄2 in. wide; covered with a sort of felt, and containing five to twelve blackish seeds. Bot. Mag., n.s., t682.
Native of California in the coast region; of unrecorded introduction. This beautiful, half-woody shrub is apparently quite hardy near London, but is sometimes short-lived, especially if grown in rich soil. Young plants, it has been noticed, will pass through a winter quite unharmed but then, a few years later, will succumb during another winter not any more severe. This is not an unusual characteristic of plants which grow so rapidly and produce seed in such abundance as this does. It points to the advisability of removing all seed-pods that are not required as soon as they are formed, also to the necessity of renewing the stock from seed (or, in the case of special varieties, from cuttings) every few years. For so beautiful a shrub this is trouble well repaid. Cuttings should be made in July and August of short side-shoots with a heel attached, and placed in gentle heat. This lupin likes a good but not close or heavy soil, and it should have a sunny position. It succeeds well on dryish banks, but does not grow so large there. The typical yellow form is very beautiful and so too is ‘Snow Queen’, which was raised by Ladham’s nursery and received an Award of Merit in 1899. It is still in commerce.
The flowers of the tree lupin appear from May to August, but are at their best in June and July.