PROPAGATION 187 



of this kind are the customary means of multiplying potatoes, 

 artichokes, and dahlias. Root cuttings may be used for getting 

 additional plants of quince, horse-radish, blackberry, sea kale, 

 phlox, butterfly weed, and the like. In such cases adventitious 

 buds are formed on the roots, although they do not normally 

 occur in this way. In the case of phlox and butterfly weed, 

 however, small roots left in the soil after the plant is dug are 

 almost certain to send up new plants, and in horse-radish and 

 sea kale the larger roots are depended upon for increasing 

 the number of plants. Dandelion roots can also originate buds 



FIG. 137. Tubers of artichoke (Helianthus) and potato, which are usually 

 propagated by tuber cuttings 



in this way, and a single piece of root left in digging may pro- 

 duce several new plants. Hoot cuttings, like tuber cuttings, 

 are entirely covered by the soil when planted. 



Hardwood cuttings. Hardwood cuttings are made from ma- 

 ture wood not more than two years old and usually younger. 

 They are cut at least six inches long and are taken late in 

 autumn when the wood is dormant. They are not set until 

 the following spring and must be kept in a cool moist place 

 until used. In common practice they are tied in bundles of 

 about one hundred each and buried a foot or more deep and 

 upside down in a well-drained spot, or they may be kept in 

 moist sand in a cool cellar. During the winter a tissue called 

 the callus forms over the cut ends, and from this or near it the 

 new roots start. In plants that root rather easily the cuttings 

 are often set out in autumn. Nearly all our trees, shrubs, and 

 woody vines may be propagated by hardwood cuttings, though 

 the form of these depends somewhat upon the species it is 



