This section is from the book "The Gardener's Monthly And Horticulturist V21", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
A paragragh has been circulating in the newspapers for the last few years and it appears as if it is to continue. As I stumble over it every month or two, I do not quite understand it, and would like more light. The paragraph is to the effect that Red Clover, Trifolium pratense, produces no seed in New Zealand, and that it is because there are no bumble bees there, so an importation from England had to be made. Now if such be the case, I have no doubt many of your readers would like to hear some of the details of the voyage of a vessel containing such a queer cargo. Who caught the B. Bs. ? And how were they caught ? And, as their lives are short, how was the race perpetuated on the voyage ? And, finally, did their presence in New Zealand cause the perfecting of the seed?
The flowers of Trifolium repens being perfect, are capable under all ordinary circumstances, of self-fertilization; but if by chance, or some climatic influence, the pollen or some of the organs should become imperfect, and to all practical purposes one plant staminate and another pistillate, the bees would be of little use from the fact that they always attend to their own business and do only one thing at a time. If they go out to gather honey they gather honey alone,not either honey or bee-bread; and if they go out to gather pollen they do so and nothing else. Now in gathering honey from dioecious flowers as in the willow for instance, they only visit pistillate flowers; and for wax only staminate ones. Again, should the flowers be all staminate, there would be no stigma to be fertilized, or should they be all pistillate, there would be no pollen to fertilize them. The only way I can see in which the bees could be of use, would be where a portion of the flowers had their pollen or reproductive organs perfect, but in that case seed would be produced without the aid of the bees, and the paragraph would be untrue. If the whole thing is not a hoax, it is probable that extreme heat, or continued wet weather has something to do with the infertility.
Extreme heat will cause the nectar or sticky substance on the stigma to dry up, and when such is the case, the pollen will not adhere to the stigma, nor will expansion of the inner sac or case of the pollen grains take place, consequently there can be no fertilization of the ovary. Wet weather will cause the honey to be dissolved and frequently both pollen and honey are washed away. The honey that is on the stigma has two offices : first, to cause the pollen to adhere to the stigma, and secondly, to keep the grains of pollen moist, and assist the inner sac to expand so that it may reach the ovary before bursting.