This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
A genus of pretty hardy flowers, of which a few species are in cultivation. They are related to the Polygonums, but, unlike the majority of that family, are neat-growing, free-blooming plants, well worth the attention of the lovers of choice herbaceous and alpine flowers. It is an American family, found chiefly on the mountains of the north and north-west of that continent. They are all best adapted for rockwork, and form beautiful tufted masses in sunny positions. Sandy loam suits them best, and the drainage should be good, but in the growing season they will take copious supplies of water with advantage. They are easily propagated by cuttings while stock is scarce; but when plentiful, abundant increase may be obtained by means of division. Trailing shoots are sent out resembling Strawberry runners, with a tuft of leaves at the points, which may be taken off and rooted in a cold frame or hand-glass in sandy loam and leaf-mould, keeping them close-shaded and moist till they are rooted, inuring them afterwards to air and light gradually. Or the shoots may be laid in the same way as Strawberry runners are laid, covering the base of the leafy extremity with sandy soil. Towards autumn the layers and shoots may be planted out in their permanent places.
They are plants by no means often seen in private gardens, but from their free-blooming quality, pretty flowers, and neat habit, it may be said they only require to be better known to be more generally grown. Their flowers are very persistent, and consequently last long.
This species reaches the height of about 9 inches, growing in rather flat masses. The leaves are evergreen and ovate, with a heart-shaped base, clothed with grey down beneath. The flowers are numerous and small, in compound umbels on simple stalks, rising well above the foliage, yellowish white, appearing in June.
Rather a smaller-growing species than the last. The leaves are ovate, hoary, with close-lying silky hairs above and below, the under side being very densely covered therewith. Flowers 9 inches high in umbels, yellowish, opening in June.
Similar in habit to both the preceding, and in foliage also, but deeper yellow in the flowers, which open about a fortnight later than the foregoing; the prettiest, best, and newest of the group.