He noted that insufficient pollination not only reduced the number of flowers that set but also resulted in imperfect fruit. Whether the self-fertile cultivars are capable of pollinating themselves in the absence of pollinating insects has not been determined on all cultivars of blackberries. The structure of the blossom strongly indicates that insects are necessary to transfer the pollen from the appropriate anthers to all of the receptive stigmas if maximum production of highest quality berries is obtained. Insufficient cross-pollination of these not only reduces the total set but results in imperfect fruit. The 'Oklawaha' cv. was developed precisely to provide a pollen source for 'Flordagrand' and to yield a marketable crop as well.
Yields largely depend upon the degree of insect cross-pollination.
They recommended that colonies of honey bees be placed in or near the plantings just before bloom. They also recommended the planting of alternate rows of 'Flordagrand' and 'Oklawaha' to provide the supply of pollen for crossing. They concluded that in all of the trailing cultivars the yields depended on the degree of effective cross-pollination. The effective time period of pollen transfer within an individual flower, as well as between flowers of blackberries has not been determined. Most pollination probably takes place the first day the flower is open with the remainder occurring the second day, although flowers will stay receptive for 3 days in a greenhouse at 75 deg F. Petals will hang on for 4 days if the weather is cool, but they usually drop off the second or third day.