How Many Days Should One Pollinate An Important Cross?
For most crosses, I only pollinate once; but if you have an important cross you may want to pollinate up to 5 days in a row. This recommendation is based on the data in the graph below:
The experimental numbers were averaged from 8 batches of 25 pollinated flowers per batch. Of course, if pollen is scarce; one has to decide whether the remaining pollen is better used pollinating another later opening flower on the same valuable plant than, say, pollinating the original hip for the third or fourth time (i.e. one has to consider the possibility of diminishing returns). Thus, this repeated pollination would be most useful in the spring with a pollen parent like William Baffin which produces almost an unlimited number of blooms to use for pollen. The data came from the following published scientific paper:
Title: FACTORS AFFECTING FRUIT AND SEED SET IN THE HYBRID TEA-ROSE 'SONIA'
Authors: d.P. de Vries and Lidwien A. M. Dubois
Authors affiliation: Institute for Horticultural Plant Breeding (IVT), P. O. Box 16, 6700AA Wageningen, The Netherlands
Published in: Acta Horticulturae, volumn 226, pages 223-230, (1988).
Authors: D.P. de VRIES, L. A.M. DUBOIS
Abstract: "In various years the effects of temperature, repeated pollination of the same flower, the time interval between emasculation and pollination and of the application of GA 4+7 on the fruit set, seed set and seed germination of roses were investigated in the large-flowered Hybrid Tea cv. 'Sonia', using 'Hadley' or 'Ilona' as pollinators.
Optimum conditions for breeding with 'Sonia' are: greenhouse temperatures between 20 and 25°C, and pollinating at least twice between 1 and 4 days after emasculation. To improve mainly fruit set, GA may be applied 7 or 14 days after emasculation, in the concentrations 10, 50 or 250 ppm.
Generalization of present results and the penetration of pollen tubes into the 'Sonia' ovary to explain maximum seed set are discussed."