The influence of propagation techniques, the rest phenomenon, and juvenility on the propagation of pecan, Carya illinoensis (Wang) K. Koch, stem cuttings

Abstract

Juvenile pecan hardwood stem cuttings were successfully propagated during the 1969-70, 1970-71 and 1971-72 dormant seasons at College Station, Texas. Semi-hardwood cuttings, because of their large leaves, were difficult to propagate and lost Ca, K, and Mg through leaching under intermittent mist. Thick diameter hardwood cuttings (14 mm) developed more roots per cutting and had a higher survival percentage than thin cuttings (9 mm). Girdling hardwood cuttings did not influence rooting or survival. Callusing as a preconditioning treatment reduced rooting and survival. Indolebutyric acid applied at 10,000 ppm as a five second "quick dip" and 21??C bottom heat were optimum for those treatments. Peat pots did not increase rooting or survival, but facilitated, transplanting. A peat:sand:soil (1:1:1) potting medium produced good cutting growth. An optimum collection period for pecan hardwood cuttings appears to be during mid-rest or at approximately 200 to 400 hours of accumulated field chilling "below 7-2??C. Cuttings collected after 500 hours have received sufficient chilling and force buds rather than roots. A chilling requirement of 400 hours below 7.2??C was recorded for 'Desirable' and 'Mahan' while 500 hours were required for 'Stuart'. Day length was shown to increase bud break throughout the dormant chilling period and could be a controlling factor in the rest phenomenon. A two phase, short day-chilling: long day-warming program could be the control mechanism in the release of rest. A consistent 40 percent survival was obtained with cuttings from juvenile wood, while less than 10 percent survival was recorded for cuttings from adult wood..