Читать книгу The Pecan and its Culture - H. Harold Hume - Страница 16

Table of Contents

Since two kinds of flowers are produced on the pecan, one bearing the pistils, the other stamens, the pollen must be transferred from the latter to the former in order that pollination may take place. In many plants the pollen is transferred from one plant or flower to another by means of insects; but in the pecan there are no bright colors, no nectar, no scent to attract insects to carry pollen, but, instead, the wind is the carrying agent and it needs no attractions. Pollen is produced in large quantities, necessarily so, since much of it is wasted.

Unfavorable weather conditions at time of blooming may, however, interfere seriously with pollination. Heavy winds or wind-storms, and rains of several days duration, may prevent the necessary and desired distribution of the pollen, as a result of which no fruit is formed.

Sometimes the staminate blooms are destroyed by frost while the pistillate ones escape. It makes little difference which is destroyed, however, as in either case the result is the same—no fruit sets.

The staminate flowers push out from the lateral buds at the same time the new shoot develops from the terminal one. The pistillate blossom does not appear until the terminal shoot has grown six or eight inches, and in the meantime it is protected by the unfolded leaves. The staminate bloom, on the contrary, is exposed from the first, having no leaves to protect it. In consequence it is much more likely to be cut off by frost. Dr. Trelease refers to several observations on proterandry (maturing of the pollen before the stigmas of the pistils) in the pecan. This, together with the unprotected condition of the staminate blooms, we believe, accounts in a large measure for the non-setting of fruit on the northern boundaries of the pecan area.

The artificial or hand pollination of the pecan is an easy matter and offers an inviting field for those interested in plant breeding. Emasculation, or the removal of the stamens from the flowers necessary in breeding so many plants, is not necessary in the pecan. All that is needed is to cover the pistillate blossoms with a sack until they are matured. At this time the inner or stigmatic surfaces of the pistils will be exposed and ready for the pollen. The pollen, collected from adjoining trees in bloom or brought from a distance, can then be placed upon the stigmas and the sack replaced. When the fruit is set, the paper sack should be replaced by one of mosquito netting. Some careful work has already been done along this line, and it is hoped that many more will take up the work. Much yet remains to be desired, and varieties may be better adapted to different sections. The ideal, large, full-meated, thin-shelled, prolific and precocious variety of pecan has not yet been brought forward. It may be accidentally discovered; it may be produced and can be produced by systematic, painstaking work in breeding. It is hoped that the number of workers in this inviting field may be increased. Some may be deterred by the fact that it will take the seedlings so long to come into bearing. But scions may be taken from the seedlings raised from cross-bred nuts, top-worked on large trees, and fruit could be obtained in many cases in a period not exceeding five or six years from the seed. Those which would not produce fruit in six years in this way might perhaps as well be discarded.