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Their Propagation: Hardy
Oriental poppies, Japanese anemones, and the anchusas may be easily propagated by means of root cuttings. Hardy chrysanthemums, phlox, arabis, hardy asters, delphiniums, and scores of other perennials are more readily increased by means of cuttings taken from young growing shoots. Hardy chrysanthemum and aster cuttings should be taken in early spring, soon after growth starts. The cuttings from arabis and Phlox divaricata should be taken immediately after the flowering period, from the young growth which then develops. Delphinium cuttings may be taken either early in the spring or shortly after the first flowering period.
In making green cuttings, the tops of the young, growing shoots should be taken. A sharp clean cut should be made directly below a leaf node and a portion of the lower leaves should be removed in order to reduce the evaporation surface. The cuttings should be inserted immediately into clean sand in a cold frame or propagating box, and should be kept well watered and shaded until rooted. After they have rooted they may be transplanted to small pots or to a frame filled with soil.
Root cuttings are very easily made. The plants are lifted and portions of the roots are cut up into small pieces, two to three inches long. These are planted much as seed would be planted, in boxes or in frames, being covered with an inch or so of soil. The same mixture which is recommended for seed boxes--that is, a mixture of one part loam, one part sand, one part leaf mould--is excellent.
Divisions The division of old plants is perhaps the most simple of all methods of propagation and one that is almost sure to give good results. Hardy asters, phlox, bleedingheart, irises, and peonies are commonly propagated in this way, as well as many other herbaceous perennials. The best time for division to be made varies somewhat with the different plants. Hardy asters and chrysanthemums should be divided in very early spring just as growth starts. Phlox may also be divided in spring, but it is better to lift the plants in September after they are through flowering, as the divisions will then have an opportunity to become established before winter sets in and will have a head start in the spring. Bleedingheart should always be divided in the autumn, never in the spring--that is, if one wishes bloom the same season. Iris may be lifted and carefully divided at almost any time from early spring to mid-autumn, but the plants receive less check and are more easily able to reestablish themselves if divisions are made immediately after the blooming season, as at this time considerable new root growth is made. Peonies should be divided in early September. It is hard enough for young peony plants to become established at best, and one should certainly do all one can to help them get the best possible start in life.
The desirability of frequent division varies with different plants. Hardy asters, chrysanthemums, phlox, and iris deteriorate rapidly if left untouched over a period of years, and much better results are secured if they are systematically lifted and divided every three or four years. Bleedingheart and peonies, on the other hand, resent interference and should never be disturbed unless it is necessary to move them to a new location or unless one wishes increase of stock. One of the most beautiful clumps of bleedingheart that I have ever seen had been growing undisturbed for over fifty years.
Where divisions are made, the plants should be lifted and pulled gently apart in order to injure the roots and crowns as little as possible. In some cases, where the crowns have become tough and hard, more strenuous methods will have to be used. A strong butcher knife or a sharp spade can be used to make a clean, swift cut.