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Effect of growth substances on the rooting of cuttings of rhododendron species

Urszula Nawrocka-Grze¶kowiak

Institute of Dendrology
Polish Academy of Sciences
Parkowa 5, 62-035 Kórnik, Poland
e-mail: ung@man.poznan.pl

Cuttings of the following rhododendron species were rooted: the evergreen R. catawbiense Michx. ‘Grandiflorum’, R. ‘Cunningham's White’, R. brachycarpum D. Don ex G. Don, R. pachytrichum Franch. (with green and red shoots), Ryakushimanum Nakai as well as the deciduous R. atlanticum (Ashe) Rhed., R. calendulaceum (Michx.) Torr., and Rviscosum (L.) Torr. The cuttings were treated with IBA (0.5, 1, 2, and 4%) in talcum powder with or without the fungicide Captan (2:1), or else with Seradix B2 (containing 0.4% IBA) and B3 (containing 0.8% IBA). The rooting level depended strongly on species. The highest percentage of rooted cuttings was recorded for R. catawbiense ‘Grandiflorum’, R. ‘Cunningham's White’, R. atlanticum, and R. viscosum, irrespective of the applied growth substance. R. brachycarpum cuttings rooted the best when 2% IBA had been applied with or without Captan. Rooting of R. pachytrichum strongly depended on the form: with red or green shoots. Cuttings of red shoots rooted much better than those of green shoots, irrespective of the applied growth substance. Cuttings of R. yakushimanum rooted the best after application of 4% or 2% IBA with or without Captan, while Rcalendulaceum after 1% IBA with 1% Captan. Application of Captan alone and Seradix B3 did not give positive effects.

Nawrocka-Grze¶kowiak U., 2004. Effect of growth substances on the rooting of cuttings of rhododendron species. Folia Horticulturae 16/1: 115-123.