Abstract
Northern bayberry (
Morella pensylvanica
) is an adaptable, semievergreen, northeastern North American native shrub where fruit-bearing female plants are highly sought after for landscaping purposes. Efficient production of female plants necessitates having a reliable method of clonal propagation because of dioecy. A tissue culture micropropagation method for northern bayberry has been developed using in vitro shoot multiplication and rooting of microshoots. Micropropagation offers propagators a reliable way to clone desirable female bayberry genotypes. Retipping, which is the repeated harvesting of miniaturized shoot tips from recently micropropagated plantlets, has been used to enhance production of some nursery crops such as lilac, mountain laurel, and rhododendron. We explored the use of repeated retipping to amplify the number of plants that can be obtained from an initial micropropagated crop of
M. pensylvanica
‘Bobzam’ (Bobbee™) plantlets. Rooted microcuttings direct from tissue culture could be used to provide three harvests of retip cuttings. Following each retip cutting harvest, the bases of the original, rooted microcuttings regenerated shoots that were suitable for a subsequent harvest of retip cuttings in only 4 weeks. The rooting ability of retip cuttings collected during the three harvest cycles did not diminish and remained high, between 90% and 100%. Retip cuttings produce between three to four roots per cutting and initiate new, vigorous shoot growth readily. Rooted retip cuttings can be acclimated to greenhouse conditions with close to a 100% success rate. Furthermore, the original, rooted microcuttings, after supplying three cycles of retip cuttings, can be grown and acclimated alongside retip plantlets to produce additional high-quality plants. Retipping can be used to produce a ∼300% increase in salable bayberry plants from just a single crop of rooted microcuttings and three retip cropping cycles.