Mpn. Gent, PACLOBUTRAZOL OR UNICONAZOL APPLIED EARLY IN THE PREVIOUS SEASON PROMOTES FLOWERING OF FIELD-GROWN RHODODENDRON AND KALMIA, Journal of plant growth regulation, 14(4), 1995, pp. 205-210
Field-grown large leaf Rhododendron and Kalmia latifolia were treated
with one of three concentrations of paclobutrazol or uniconazol in Apr
il, June, or August in the second year from propagation. The elongatio
n of stems was measured as was the number of flower buds initiated. Sp
ray applications in April or June increased flowering at the lowest co
ncentrations tested; 4 mg . L(-1) paclobutrazol and 1.5 mg . L(-1) uni
conazol. Flowering was induced in cultivars that normally did not flow
er, and the number of flower buds per plant was increased in cultivars
that normally flowered. All treatments that induced flowering also re
duced stem elongation. Spray application in August failed to enhance f
lowering. At the concentrations tested, uniconazol was more effective
than paclobutrazol in increasing the number of flower buds and reducin
g stem elongation of Rhododendron. For Kalmia, there was less response
to the concentration of growth retardant, and the two chemicals enhan
ced flowering equally.