While there are many species of this popular genus there are only three that have come into popular favor. These are Paeonia albiflora, P. Moutan and P. tenuifolia. Paeonia albiflora, the Chinese hardy herbaceous peony, is the section the florist is mostly interested in. P. tenuifolia is interesting and can be used with good effect in the herbaceous garden. Its finely divided foliage is very distinct, with solitary terminal flowers. The typical color is scarlet or crimson, but other colors have been produced of late.
The Moutan section is the so-called tree peony. These varieties are shrubby and much branched. The double forms have beautiful flowers. Most of the varieties now in cultivation have large double flowers of various colors. They are propagated by grafting the dormant eyes on strong roots of the herbaceous species. The tree peony makes a handsome subject for the lawn, or is fine in masses in a bed, and it also is much used for forcing for conservatory decorations, but it will scarcely pay the American florist to attempt the forcing of this showy plant. We have tried it. In the first place the plants of useful size are expensive, and if not large enough to give you a profusion of bloom they are not attractive. If the practice of grafting the tree peony becomes common in this country and moderately bushy plants can be purchased from specialists at a reasonable price, they would soon become popular forcing plants.
Paeonia albiflora, the herbaceous peony of China, is the commercial plant which of late years has grown greatly in popular favor. It comes from China, northern Asia, and Siberia. This accounts for the extreme hardiness. The single varieties are the typical form and have wide-spreading petals with a bunch of yellow stamens and anthers in the center, making a very showy flower, but it is the double varieties that are in fashion and demand. Of these there are hundreds of garden varieties, so a list of names given today may be out of fashion in five years. All I shall say about varieties is that at least seventy-five per cent of all you plant for cutting should be white and light pink. There is great variation in these shades, so consult the catalogues of the peony specialists.
If planting with the intention of dividing and selling divisions of the roots, they can be planted three feet apart each way, or even closer in the rows, but if planting for future cutting of the flowers, then four feet apart each way is little enough room.
While the peony will exist in almost any soil, it will give only poor flowers in a shallow, sandy or gravelly soil and it should be deep, heavily manured and inclined to be moist. To get the best results the soil should be not only ploughed or dug, but it should be trenched to a depth of two feet, working in thirty tons of cow manure to the acre. Frequently in our northern summers we get a protracted spell of dry weather the latter part of May and early June; then the peony blossoms suffer. I have seen them much injured at this time in a dry spell, so if planting for cut blossoms it would be well to choose a piece of ground with a slight fall to the south, so that when occasion arrives you can irrigate the plot. No other means of watering would be practical or efficient. Peonies do very well in partial shade. Bordering a plantation of hardy shrubs and shaded by trees, they are very satisfactory; but for the commercial man, give them the full sun.
Next to a deep, rich soil is the necessity of keeping the peony field clear of weeds and, therefore, if the plants are planted four feet apart each way in straight rows, much of the cleaning and cultivating can be done by horse cultivator, leaving only a small space to be tended with the hand hoe. If the dandelion and other coarse weeds and grasses are allowed to get a foothold in the crown of the peonies, they will be very troublesome, so they should be kept rigorously free of weeds.
The herbaceous peony sends up long, strong flower-stalks mostly terminating in four to six buds. The largest and most perfect bud should be selected and the others removed unless you wish to have some flowers later, when later buds can be left and the others removed. Peonies should be cut in the bud state and kept for twenty-four hours in a cool room or cellar. If allowed to open in the field they travel badly and soon have a wilted appearance. Their season of use is often prolonged by cutting the flower stalks and buds when quite tight, or as soon as the buds show color, and keeping them in water in cold storage, a degree or two above the freezing point.
They are propagated or increased most easily, either in early spring or fall. September or October is the most favorable time. If you wish to slightly increase your stock you can divide strong clumps into two or three sections, but if desirous to greatly increase some choice variety, any piece of strong root with an eye will do and in three years from a single root and eye you will have a strong clump of flowering roots. The autumn is the most favorable time for planting peonies, and it is then nurserymen usually ship.
To me it is doubtful if forcing of the peony can be made profitable. If you receive an order for some special occasion you would have to get it two months ahead of time. The forcing of peonies is exactly like that of rhubarb. The roots should be dug before frost, placed in a coldframe and protected by some material like light stable litter or leaves, and brought into heat about eight weeks before the flowers are wanted. We think that the price obtained does not warrant the operation, unless for a special occasion, and then notice must be given in time.
The extent of the latitude of our continent admits of the peony being in season for several weeks. The southern flowers command a high price and gradually the flowers of Pennsylvania, Ohio, southern New York, and at last our northern flowers, are coaxed into blossom by the strengthening sun, and wherever they blossom they are favorites and in demand.
One word of advice to the florist of small ground or capacity - fifty clumps of well cultivated plants will make you more profit than an acre of neglected peonies.