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Horticulture Digest

Date Last Edited:  08/24/2001

Hawaii Cooperative Extension Service

Horticulture Digest #103

Air layers are generally used to produce large plants of Ficus benjamina for interiorscape use. The plants root in 4 to 6 weeks and are then cut and planted 2 or 3 per container. Leaf loss is often significant, and lower branch structure is highly dependent on the choice of the limb that was layered. Growers often need to prune the layers to achieve a more dense plant.

For these reasons, it is desirable to increase the number of branches on existing twigs and main stems of airlayered F. benjamina. As noted, pruning to shape the plants is one option; another could be the use of chemical branching agents to stimula te dormant lateral buds into growth. This research was conducted to determine whether the growth regulator could substitute for pruning, and if not, when was the best time to apply the growth regulator.

Variation was great among the treatments with some plants reacting adversely to pruning and dying. Table 1 shows that pruning was necessary to stimulate bud break, although the treatment with BA applied prior to pruning had the poorest percentage of shoot s with new breaks. Application of BA at the time of pruning yielded a slightly higher proportion of shoots with breaks than did pruning alone. In considering the proportion of buds on each shoot which responded to treatment, a similar edge was demonstrate d for the BA application at time of pruning.

Table 1. Percentages of branches of F. benjamina which showed new breaks 4 weeks after treatment and the proportion of buds producing new breaks on these branches in response to application of BA and/or pruning.

                    Percent of         Percent
                    branches with      bud break
Treatment           bud break          per branch

Not pruned, No BA     36.4               11.3

Not pruned, +BA       35.8                6.2

BA 6 days before
pruning               27.2               10.6

Pruned, No BA         72.0               29.7

BA at pruning         83.3               41.4

Pruned, No BA         74.0               31.1

Despite the unexpected result for the third treatment, the work bears repeating. Higher concentrations of BA should be evaluated. Pruning definitely improves bud break even without BA, and BA does not appear to substitute for pruning. The question is whet her BA can improve bud break economically. Additional attention could focus on whether plants which have survived a long time in a low light interior can be rejuvenated by judicious pruning and cytokinin treatment.

Thirty l-gallon pots, each containing 2 air layers of F. benjamina were established in a glasshouse at the University of Hawaii. They were watered twice daily with a liquid feed program supplying 200 ppm each of N and K. The medium was 1:1:1 soil-p eat-perlite supplemented with treble superphosphate and dolomite. When the plants were well-established, treatments were initiated.

Cytokinin, as N-6-benzylamino purine (BA), was applied as an aqueous foliar spray at the concentration of 250 ppm plus 0.05% Tween 20 spreader.

One group of plants was not pruned. One group was sprayed with BA 6 days before pruning, and the third group was sprayed immediately after pruning. All pruning was done on the same day. One half of each group did not receive BA and served as controls. The re were 5 single pot replicates of each of the 6 treatments.

Ten branches were tagged on each pot and the number buds, both elongating and dormant, were counted from the tip to the origin of the branch. After 4 weeks, the number of elongating shoots on each branch was counted. Data are expressed as the percent of a ctual versus potential breaks which could develop after treatment.

Richard A. Criley, criley@hawaii.edu

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