PROPAGATION OF TREES AND SHRUBS 9 



Root-inducing Substances Sold Under Trade Names 



These have given results not significantly different from those secured 

 by the use of the pure chemicals (83, 113). They improve the rooting of 

 cuttings of some species if properly used. That usually means as recom- 

 mended by the manufacturers, although their recommendations, like those 

 of the experiment stations for use of the pure chemicals, are probably 

 sometimes tentative and may not finally and in all cases prove tci be the 

 best (102). Rootone contains alpha naphthylacetamide and the Hormo- 

 dins contain indolebutyric acid. As v/ith indolebutyric acid, so with Hor- 

 modin A, rooting response varies with the season and conditions under 

 which cuttings are taken, treated, and handled (117). One B T I unit 

 in Hormodin A, as now made, is equivalent to indolebutyric acid 1 mg./l., 

 a point of interest when a recommendation for optimum concentration of 

 one of these materials is being followed in diluting the other. 



Treatment of Hardwood Cuttings 



Hardwood cuttings of most trees and shrubs respond less to treatments 

 with root-inducing substances than do softwood cuttings (25, 57, 114, 130), 

 but rooting of hardwood cuttings of a number of species including grape 

 (130), Tatarian honeysuckle (40), oriental bittersweet (48), black locust 

 (95), poplars (65), and Deutzia (48) has been improved or hastened by 

 treatments. Rooting of hardwood cuttings of common privet was not affect- 

 ed by callusing before treatment (57), but treatment of hardwood cuttings 

 of pecan and some other species was more effective if cuttings were al- 

 lowed to callus before treatment (95). Such cuttings rooted, if, immediate- 

 ly after treatment, they were packed in moist san4 or sphagnum at 68° to 

 70° F. for a week and then planted in the field (95); and hardwood cut- 

 tings of apple, grape, and Hibiscus responded to treatments when buried, 

 after treatment, in damp peat moss at about 75° F. (58). 



Deferred Treatment or Re-treatment of Cuttings 



Cuttings are usuallj' treated with a root-inducing substance very soon 

 after they are taken if they are treated at all. If, however, they have not 

 rooted, either with or without treatment, cuttings of some species may be 

 removed from the rooting medium and effectively treated, without remov- 

 ing callus (48), weeks or months after they were first inserted. Such 

 treatments are called "deferred" if applied for the first time; "re-treat- 

 ments" if applied for the second time. 



Rooting of cuttings of box, Japanese yew, and a variety of Camellia japonica 

 was improved when treatments were first applied to cuttings six weeks 

 to five months after they were taken (48). A treatment first applied to 

 cuttings of American holly after they had remained unrooted in the bench 

 for eleven weeks was beneficial (101). A first treatment of cuttings of 

 incense cedar (see page 25) with indolebutyric acid fifteen months after 

 they were taken was decidedly effective. 



Cuttings of some species which respond little or not at all to an initial 

 treatment will root or root better if re-treated (61). Rooting of cuttings 

 of Hamlin sweet orange was improved by re-treatment three weeks after 

 the initial treatment (19). Re-treatment of cuttings of papaya and Camel- 

 lia (19), after callus had formed on the latter (61), gave similar results. 

 Other species which responded well to re-treatment are Japanese yew and 

 Pfitzer's juniper (59). 



