A Report on the Effectiveness of a Chemical Treatment for Inducing the Formation of Flower Buds
By David G. Leach, Brookville, Pa.
Hybridists and nurserymen have been interested for years in treatments designed to induce the formation of flower buds on rhododendrons. Constriction of a stem with a rubber band has been alleged to produce a bud at the terminal of the branch. A carefully controlled treatment with a very small amount of 2,4-D, and other more drastic measures have been claimed to be effective in varying degree.
In 1956 a West Coast research foundation circulated a mimeographed report describing their success in inducing flower bud formation on rhododendrons and other plants by spraying them with a mixture of potassium hydroxide, phosphoric acid, Boric acid, sugar and water. This spray was designed to raise the carbohydrate level in relation to the nitrogen level in the plants, and to provide at the same time the phosphorus, potassium and boron which are important constituents in the formation of floral buds. The treatments were thought to be so successful that the formulation was given a commercial brand name for sale to the public.
Using the same formula, I treated alternate rows of rhododendron seedlings of identical parentage in 1957 in my trial grounds and the results failed to confirm any part of the success previously reported on the West Coast.
Six rows containing a total of 194 seedlings five years old from the cross 'Mars' x catawbiense var. rubrum were selected for the experiment. The second, fourth and sixth rows were sprayed with the material on July 12th, on July 26th and again on August 25th. The first, third and fifth rows were untreated.
On October 15, 1957 a count was made to determine the effectiveness of the treatments. The treated rows contained a total of 101 plants which had an average of 1.23 buds per plant. The untreated rows containing 93 plants had an average of 1.50 buds per plant.
The evidence from this limited trial suggests that the bud-inducing formulation is not effective under the nutritional conditions prevailing in my trial grounds, which are thought to be roughly representative of those which are generally encountered in the northeastern United States. The 22% greater bud formation on untreated rows should be statistically significant and might indicate that the material actually inhibited the setting of flower buds. However, the experiment should be repeated with larger numbers of plants before arriving at any such conclusion.
There is at least a preliminary indication that the bud-inducing material is ineffective under conditions which are not known to be exceptional for the eastern United States. It seems plausible that there must be present in the plants a level lower than optimum of one or more of the components in the spray for the treatment to result in an increase in the number of buds formed.
In any case, despite the enthusiastic speculation of hobbyists, so-called bud-inducing products of this character are no magic cure-all for producing large quantities of flowers on rhododendrons.