This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Herbs or undershrubs with alternate stipulate leaves and racemose, paniculate or spicate bisexual flowers. Bracts ochreate. Perianth usually coloured, of 5 nearly equal segments, the three outer sometimes enlarging over the flattened or trigonous fruit. Stamens 5 to 8; anthers versatile. The species are estimated at 150, and are dispersed all over the world. There are twelve indigenous species, mostly weeds. The generic name is composed of many, and yovv, knee, from the numerous joints of the stems.
1. P. cuspidatum, syn. P. Sieboldii. - This is a tall hand-some perennial, belonging to the foliage section of ornamental plants. It grows from 4 to 8 feet high, and bears an abundance of large somewhat distichous oval-oblong cuspidate petiolate leaves. Flowers white, in drooping racemes, succeeded by scarlet fruits. A native of Japan, flowering in Summer.
2. P. Brunonis. - A dwarf perennial species, rarely exceeding a foot in height. Leaves petiolate, oblong-lanceolate, acute, with a cartilaginous margin. Flowers rosy red, in dense terminal spikes appearing in Summer. Northern India.
3. P. Bistorta. Bistort or Snake-root. - This is a rare indigenous species, and the handsomest we have. Leaves chiefly radical, large, oblong or ovate-obtuse, glaucous beneath, on long petioles. Flower-scapes erect, furnished with a few sessile leaves, and terminated by a solitary erect dense spike of reddish pink flowers, produced from June to September.
P. amphibium is a perennial aquatic or semi-aquatic native species. When growing in water the petioles are very long and the stipules smooth, whilst the terrestrial form has short petioles and hispid stipules. The flowers are bright red.
4. P. vaccinifolium. - This is a desirable creeping branched sub-shrubby species. Leaves small, oblong-ovate, acute, with slightly revolute margins. Flowers bright rosy red, in numerous terminal spikes towards the end of Summer. Native of Northern India.
5. P. orientale. - A tall annual species from 3 to 4 feet high. Leaves large, ovate-acuminate, pilose or nearly glabrous. Flowers deep rosy purple or white, in long drooping racemes. Northern India and China.