• 4 . Reprinted from the JOURNAL OF FORESTRY, Vol. 61, No.5, May 1963 Vegetative Propagation of Aspen by Greenwood Cuttings! Abstract. Greenwood stem cuttings taken from root suckers of Populus tremuloides and P. gmnd'identata were rooted in coarse sand under both inter- mittent mist and polyethylene sheet- ing in a greenhouse and under mist in an outdoor propagation bed. Pre- rooting treatment of cuttings with aqueous solutions of lBA (20-100 p.p .m.) stimulated rooting. P. grandi- dentata cuttings were more difficult to propagate than those of P. tremu- loides. Fungal and bacterial infection accounted {or high mortality of cut- tings in some experiments. Although most members of th e genus Populus may be propagated vegetatively with ease, section L ence sp ec ies (aspens) are diffi- cult to r egellerat e. In the United Stat es only a few reports hav e b ee n published (1, 6, 7). European foresters, on th e other hand, have devoted considerable attention to propagation of P. tremula and have developed several techniques cur- rently in use on a commercial scale (2, 3, 4, 5, 8). In the experiments reported here, greenwood stem cut- tings tak en from young root suck- ers of P. tremuloides and P. gran- didentata were rooted using an adaptation of a European tech- nique describ ed by Muhle Larsen (4) . Newly initiated aspen suckers were obtained from (1) 4- to 6- inch-long root cuttings (Fig. 1) cultur ed in sand und er greenhouse co nditions and (2) clones clear cut near Pells ton, Mich. Greenwood cuttings (Fig. 2) were mad e from the suckers and treated with aque- ous solutions of indolebutyric acid (IBA) ranging in concentrati on from 0 (control) to 100 p.p.m. (Bases of cuttings were placed in solutions for 24 hours.) After TBA treatment, cuttings tak en from cultured root sections were rooted und er polyethylene sh ee t- ing or intermittent mist in a gr een- house. Field-collected cuttings were propagated under mist in an outdoor bed located near th eir sourc e. A coarse sand medium was used in all the rooting trials. Approximat ely 2,000 P. trenw- loides and 1,600 P. grandidentata cuttings were used in a series of small-scale experiments conducted during 1959 and 1960. In each trial, cuttings from one or mOre clones were divided into equal lots, each of which received a preroot- ing lBA treatment. Th ese clonal lots were planted in adjac ent row ;;; with bases of cuttings set 0.7 to 1.5 inch in the medium. Individual expe riments lasted two weeks in the greenhouse and three to four weeks in the outdoor bed. During t his time, weekly checks were made to determine the general condition of cuttings and the degree of root formation. After the allotted root- ing period, rooted cuttings were transferred to clay pots filled with loam soil and gradually decreasing atmospheric humidity over a one- to thr ee - week period. Under greenhouse conditions, as high as 87 percent of the untreated P. tr emuloid es cuttings developed roots, while 94 percent of those treated with 20 p.p.m. lBA rooted. Fungal and bacterial infection ac- FIG. l. - Three·inch-long root cutting of FIG. 2.-Greenwood cuttings of Populus grandidentata rooted under mist in an Pop1tlus Ir emn70ides with suckers. ontdoor propagation bed.
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• 4 . Reprinted from the JOURNAL OF FORESTRY, Vol. 61, No.5, May 1963
Vegetative Propagation of Aspen by Greenwood Cuttings!
Abstract. Greenwood stem cuttings taken from root suckers of Populus tremuloides and P. gmnd'identata were rooted in coarse sand under both intermittent mist and polyethylene sheeting in a greenhouse and under mist in an outdoor propagation bed. Prerooting treatment of cuttings with aqueous solutions of lBA (20-100 p.p .m. ) stimulated rooting. P. grandidentata cuttings were more difficult to propagate than those of P. tremuloides. Fungal and bacterial infection accounted {or high mortality of cuttings in some experiments.
Although most members of the genus Populus may be propagated vegetatively with ease, section L ence species (aspens) are difficult to r egellerate. In the United States only a few reports have been published (1, 6, 7). European
foresters, on the other hand, have devoted considerable attention to propagation of P. tremula and have developed several techniques currently in use on a commercial scale (2, 3, 4, 5, 8). In the experiments reported here, greenwood stem cuttings taken from young root suckers of P. tremuloides and P. grandidentata were rooted using an adaptation of a European technique described by Muhle Larsen (4) .
Newly initiated aspen suckers were obtained from (1) 4- to 6-inch-long root cuttings (Fig. 1) cultured in sand under greenhouse conditions and (2) clones clearcut near Pellston, Mich. Greenwood cuttings (Fig. 2) were made from the suckers and treated with aqueous solutions of indolebutyric acid (IBA) ranging in concentration
from 0 (control ) to 100 p.p.m. (Bases of cuttings were placed in solutions for 24 hours.) After TBA treatment, cuttings taken from cultured root sections were rooted under polyethylene sheeting or intermittent mist in a greenhouse. Field-collected cuttings were propagated under mist in an outdoor bed located near their source. A coarse sand medium was used in all the rooting trials.
Approximately 2,000 P. trenwloides and 1,600 P. grandidentata cuttings were used in a series of small-scale experiments conducted during 1959 and 1960. In each trial, cuttings from one or mOre clones were divided into equal lots, each of which received a prerooting lBA treatment. These clonal lots were planted in adjacent row ;;; with bases of cuttings set 0.7 to 1.5 inch in the medium. Individual experiments lasted two weeks in the greenhouse and three to four weeks in the outdoor bed. During t his time, weekly checks were made to determine the general condition of cuttings and the degree of root formation. After the allotted rooting period, rooted cuttings were transferred to clay pots filled with
loam soil and ~xposed t~ gradually decreasing atmospheric humidity over a one- to threeweek period.
Under greenhouse conditions, as high as 87 percent of the untreated P . tremuloides cuttings developed roots, while 94 percent of those treated with 20 p.p.m. lBA rooted. Fungal and bacterial infection ac-
FIG. l.- Three·inch-long root cutting of FIG. 2.-Greenwood cuttings of Populus grandidentata rooted under mist in an Pop1tlus Iremn70id es with suckers. ontdoor propagation bed.
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counted for considerable mortality, however, an-d several experiments were failures for this reason. In the outdoor bed, the following liverage rooting response for quaking aspen was observed during the summer of 1960:
N11.mber cllttings
P(,l'ccnt !·oof.r?r!
Control 627 27 20 p.p.m. IBA 320 54 50 p.p.m. IBA 402 62
100 p.p.m. tEA 50 72
P. grandidentata was more diffi ·· cult to propagate than P. trcl1W· loides, but as high as 67 percent of the cuttings treated with 20 p.p.In. IBA rooted in the greenhouse under polyethylene; 37 percent of the control cuttings developed roots. In the outdoor trials with bigtooth aspen during the sumtner of 1959, three IBA treatments (10, 20, 50 p.p.m.) stimulated 60 to 70 percent rooting, while 2!) percent of the controls rooted. However, during the following season only 20 to 3() percent of the treated P. grandidentata cuttings rooted due to a high incidence of fungal infectiOll and subsequent mortality.
Well-rooted cuttings of P. tremuloides hardened off easily and could be transferred from the outdoor bed to a low humidity environment within two weeks after potting. P. grandidentata cuttings rooted in the outdoor bed required more gradual removal from the mist to avoid desiccation. Cuttings of both species which were rooted in the greenhouse survived well under greenhouse conditions after one week in a polyethylene enclosure. IBA-treated cuttings of both species typically had more numerous and better developed roots than controls (Fig. 2), and consequently they had better survival.
Propagation of the American aspens by the above methods is not recommended at present for commercial use. The techniques may be of considerable utility, however, in propagation programs associated with . tree improvement or tree physiology research.
IThis 3tudy was supported flnancially by a g:'ant from the Lower Michigan Pulpwood Research AS80eiation and was eonducted at The University of Michigan.
Literature Oited 1. AFANASIEV, M. 1939. Effect of indo·
lebutyric add on rooting of green·
. ..
wood cuttings of some deciduolls for· e~t trees. Jour. Forestry 37 :37-41.
2. FROLICH, It. J. 1957. Die \"ogetatiye Vermehrllng "on Aspe lind Oraupap· pel un ihre Bedeutung fUr den Wald· ball. AI1/tclneine Forst.zeitschrift, Nr. 14/15.
3. KUCHU;N Z, F'RiEDRlCIt. 1958. Untet· suchungen liber die giiilstiste Wurzel· stecklingsliinge und st.arke bei der "egetativcn Vermehrtlng von Pappeln der Sectioll Leuce durch Wurzelstec.\(· tinge. Der Zlichter, 28 Band, Heft T, 336-343.
4. MUHLE LARSEN, C. 1943. Stikl;nger of urteagtige skud paa rpdder of baevreasp og granpoppel. Dansk skoy· foren Tidsskr. 28:96-113.
5. SCHROCK, OTTo. 1958. Die Graup· appel ntld ihre vegetative Verlnehrung. Der Ziichter, 28 Band, Heft 2, 71-80.
.JOURNA[, OF FORESTRY
6. SNOW, A. O. 1938. Use of illdolebu· tyrie llrid to stimulate the rooting of dorma.llt nspcn cuttings. J our: For· estry 36: 582-587.
7. TliIMA:<N, K. V., nud A. L. DELtSLE. 1 !J::9. The vegetative I'ropngation of difficult plants. Jour. A11\' Arb. ~3:
\ 103-109. 8 . . THihDJ.J.F.R, K. 1957. UnterS\1chungen
zllr \'cgdativen Vermehrullg \'Ol! FOplI/IIS t remllia L. durch Oriisteck· 1inge mit H Hfe SYIl theti~chcr W nchs· stotIe. Dtseh. Akad. Lalldwirtschaft· swiss.' Wiss Abhandlungen. Beitriige sur Pappelforschllng II. Nr. 27, 179-203. .
ROBERT E. FARMER, .JR. Southerli Harclwood LaboratoT:lf,
Southern Forest Expt. Sfa., Foi'est Service, U. S. Dept. A,qric.,
