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.
Tufted perennials with crowded radical leaves and scapose umbellate flowers. Calyx tubular - campanulate, 5-toothed, usually persistent. Corolla salver-shaped, erect or spreading. Capsule splitting into 5 entire or bifid valves. About fifty-species are known, mostly European and Asiatic, a few extending to North America. The name is derived from primus, first, from the early flowering season of the species originally described.
1. P. vulgaris, syn. P. acaulis. Primrose. - This plant is so well known that we need do no more than point out the differential characters. This is necessary, because the species have been confused, and because some of the cultivated forms appear to be intermediate between this and the next. Leaves tufted, sessile. Umbel sessile, giving the pedicels the appearance of being solitary. Calyx-tube inflated, angled; lobes acuminate. Corolla usually pale yellow, with a flat limb. The variety caulescens (elatior of early English botanists), and commonly known as the Oxlip, has the umbel stalked and the calyx villous; but the true P. elatior is only found in the eastern counties, and there sparingly. This is said to differ from the variety caulescens, and hybrids between P. vulgaris and veris: from the former in the less inflated calyx, inodorous flowers, and capsule longer than the calyx-tube; and from the hybrids in the more villous calyx, paler flowers, and absence of folds at the mouth of the corolla-tube.
2. P. veris, syn. P. officinalis. Cowslip. - This is readily known by its leaves being more narrowed towards the base, the calyx-lobes being obtuse, and by the corolla-limb being cup-shaped and deeper coloured.
The cultivated varieties, either natural or hybrid, which are generally referred to the two preceding species, are numerous. The Polyanthus, P. variabilis (fig. 200), is intermediate in character, but its origin is not known with certainty. However, as some of the forms approach the Cowslip, and some the stalked variety of the Primrose, there seems to be little doubt that it is a fertile hybrid between these two species, if indeed they are enticed to that rank. The colouring is endless in its variations, though limited to various shades and combinations of purple, red, and yellow. There is a curious variety called the Hose-in-hose, remarkable for the calyx being an almost exact counterpart of the corolla. Another race of cultivated varieties belongs to the Primrose, agreeing with that in having the flower-umbels sessile. The flowers are larger, however, in the so-called typical form, and hence it has received the name grandiflora. The varieties in cultivation are more or less double, and range from nearly pure white, yellow and lilac to deep crimson.
Fig. 200. Primula variabilis. (1/4 nat. size.
Fig. 201. Primula Sinensis. (1/4 nat. size.)
3. P. Sinensis (fig. 201). Chinese Primrose. - This species is almost hardy, or perhaps quite in favoured localities of the South-west. In cultivation it is usually restricted to the conservatory and window, where it forms one of the most attractive objects throughout the Winter.
4. P. Auricula (fig. 202). Common Auricula. - Probably no other Alpine plant has received so much attention from British gardeners as the present, having been in cultivation for nearly three centuries, and many of the best varieties having been raised in this country. It differs from its nearest allies in having oblong-lanceolate or obovate more or less minutely glandular - toothed fleshy and glaucous mealy leaves. The flowers are normally yellow and somewhat velvety, but from the effects of culture they have assumed all the shades of yellow, maroon, and purple, the latter sometimes almost black, and in some there are tints of greyish green or blue, due in part to the presence of a glaucous meal like that on the foliage. The most esteemed varieties combine two or three different tints arranged in concentric circles. They are divided into several groups, according to the disposition of the colours. The English classification includes five variations, namely : 1. Green-edged. 2. White-edged. 3. Grey-edged. 4. Selfs; and 5. Alpines.
Fig. 202. Primula Auricula. (1/4 nat. size.)
Nos. 1, 2, and 3 are sufficiently explanatory. Selfs are those double or single-flowered varieties with a uniformly yellow, purple-brown, purple, or violet limb and a white eye. Alpines are distinguished by having the margin of two blended colours, or at least by their not being separated into distinct bands, and by the yellow centre.
5. P. Japonica. Japanese Primrose. - This is a very handsome hardy species of quite recent introduction. It is glabrous in all its parts, having large oblong-spathulate coarsely irregularly and sharply-toothed sessile leaves, and tall scapes from 1 to 2 feet high bearing about 5 or 6 whorls of showy variously-coloured flowers about an inch in diameter. There are crimson, maroon, lilac, rosy-pink, and white varieties with a differently coloured eye already in cultivation. If easily grown there is no doubt that this species will rapidly spread, as it is one of the most beautiful of dwarf hardy perennials. It is a native of the island of Yeso.
6. P. farinosa. Bird's-eye Primrose. - This is a mountain plant of wide distribution, occurring in the North of England and in Scotland. It grows from 4 to 6 inches high, with small obovate-spathulate leaves clothed with a white or yellow mealy indumentum on the under surface. Scape exceeding the leaves, and bearing an umbel of small lilac-red flowers with a yellow eye.
P. Scotica, found in the extreme North of Scotland, differs in its broader petals.
We might include several more species if we had the space at our disposal, but we must be content with quoting the names of a few of the best. They are for the greater part mountain plants, requiring special care and treatment.
P. cortusoides, rosy flowers, Siberia; P. minima, rose and white, Alps; P. Munroi, tall, white, North India; P. villosa, purple, Alps; and P. amaena, bright rosy-purple umbellate flowers, from the Caucasus. The last is a particularly hand-some plant.