This section is from the book "The Gardener V3", 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.
These may be grown planted out in rich ground in the same way as the others till September, when they may be lifted and potted or planted in frames closely, and afterwards merely protected from severe frost, and kept well aired in all open weather. Of course, if they are intended to be placed about rooms, they must be put in pots at the time they are removed from the open air, and they may be forced in mild bottom-heat with much more convenience if the plants are in pots than if they are planted out in frames. All the varieties are easily increased by cuttings made of the stout short runners, rejecting all that are wiry and hard; and they should not be taken off plants that have been forced, as these are deficient in vigour. Plant them in rich fibrous very sandy soil, in a frame facing northwards; keep them close till they begin to grow, then give air, a little at first, gradually increasing it till the lights may be dispensed with wholly till the return of winter, when they will require to be put on, and the plants protected during frost. In the beginning of April they must be planted out, and everything possible done to encourage vigorous growth, on which depend the quality and quantity of bloom more than anything else.
Some raise their stock from seeds sown annually; and it is a good plan, but more troublesome in the matter of attention, and requiring more labour, than either division or cuttings, while the result in bloom is nothing superior. Among the varieties of Sweet Violets, the Czar, the King, and Giant are the largest flowers and stoutest stalks, and are consequently best for cutting; but I have not found either superior to the common Russia, in single or double flowers, for continuous and sustained bloom, while nothing surpasses the Neapolitan for forcing.
This is a very rare plant in gardens, and a very distinct species. It grows about 6 inches high, in rather tufted fashion, with palmated or five-lobed coarsely-toothed hairy leaves, and rather large purple flowers on stout short stalks. Native of North America. Best adapted for culture on rockwork, in deep rich gritty loam, in shade. Flowers in late spring and early summer.
This is related to the last, but is even a finer species, and about as rare. It grows about the same height, and is very compact and neat in its style. The leaves are cut into seven narrow lobes, the basal and the central ones usually deeply notched. The flowers are large, dark blue, carried well above the leaves on stout stalks. Best adapted for rockwork decoration in deep moist sandy soil, in shade. Native of North America. Flowers in late spring and early summer.
This is a south European species, with much of the habit of the two preceding. The leaves are broadly ovate in outline, and divided almost to the midrib, giving the appearance of a broadly pinnate leaf, and the divisions are notched at the point. The flowers are smaller than in either of the two preceding, nor are they thrown so high above the foliage, but they are rich dark violet, and in this respect they are superior to those of the others. It requires the same treatment in cultivation, and is adapted to the same purposes as palmata and pedata, and flowers about the same time.
This is a Patagonian species, and one of the handsomest of the family. It grows in tufted masses, producing bluntly egg-shaped leaves, with a heart-shaped base, toothed and hispid, as is every part of the plant outside the corolla, and inside also it is somewhat bearded. The flowers are large, bright yellow, on slender stalks, but raised considerably above the foliage; the lower petal is beautifully penciled with narrow dark red lines, suitable only for warm partially-shaded positions on rockwork or for pot-culture, and delights most in rich fibrous loam with a good allowance of grit in it.
The garden varieties of the Pansy are so familiar and so much admired by everybody that they scarce require praise or description; the mere mention of their name is sufficient recommendation. It is less of the finer florists' varieties or show sorts that I would speak than of the Fancy or Belgian and bedding ones. They will be found most useful for planting in the front line of the mixed border and on rockwork. The Fancies bloom very freely and for a long period if the soil is moist and rich; and they present most novel and pretty colours and unions of colours. But for continuity of bloom and general decorative usefulness and hardiness all kinds of Pansies are eclipsed by the bedding sorts. The Cliveden blue and yellow were the first of the race to which general attention was drawn, but they are now rapidly increasing in numbers and in improvement, and no doubt will continue to do so for some time. The Pansy delights in strong rich loam with a little sand in it, and is most sustained in its bloom when shaded for some part of the day, and copious moisture can hardly be overdone in the growing season.
Violaceae tricolor is a native of Britain, and it is the reputed parent of all the races of Heartsease. Other European species, there are good grounds for believing, have had something to do with the origin of these favourite flowers; but in the mixed and confused condition of the cultivated varieties now, it is impossible to determine with any accuracy their parentage, but the probability is that tricolor and altaica give rise to the Pansies between them.
The few species described above do not nearly exhaust the list of plants valuable for ornamental purposes comprised in the group. They are only a few of the best, and the following list contains others well worthy of cultivation in larger collections: -
Violaceae alpina, 4 to 6 inches, dark purple, Violaceae amoena, 4 inches, dark purple, Violaceae biflora, 4 inches, yellow, in pairs interesting and pretty. Violaceae blanda, 6 inches, white,
Violaceae Canadensis, 6 to 8 inches, pale blue.
Violaceae cucullata, 6 inches, dark blue.
Violaceae palmaensis, 4 inches, blue and white.
Violaceae striata, 6 inches, blue and white.