Some fruit trees require cross-pollination and companion plantings.
Cross-pollination needs to occur with a suitable variety.
1806) was the first to study the pollination of flowers and to draw attention to the necessity of insect visits in many cases; he gave a clear account of cross-pollination by insect aid.
The cleistogamous flowers are developed before or after the normal open flowers at seasons less s-- favourable for cross-pollination.
Cross-pollination may occur between two flowers on the same plant (geitonogamy) or between flowers on distinct plants (xenogamy).
Sprengel came very near to appreciating the meaning of cross-pollination in the life of plants when he states that "it seems that Nature is unwilling that any flower should be fertilized by its own pollen."