The tomato plant has the remarkable ability to self pollinate itself using the same flower because each flower contains both male and female reproductive organs. Pollination in nature is achieved by the wind, which vibrates the plant and helps spread pollen from the anthers to the stigma. Even a gentle breeze can achieve pollination. Bumblebees aid in pollination by using their flight muscles to shake the pollen loose from the flowers anthers during pollen collection according to the North Carolina State University.
The ideal time for tomato flower fertilization to take place is between 11 a.m. and 4 p.m. according to Washington State University. The weather should be dry and the conditions sunny to promote fertilization. For tomato plants planted outside in the home garden, gently shake to encourage pollination.
Night temperatures that dip below 55 degrees or rise above 75 degrees can stunt the growth of the flowers' pollen tubes which will decrease fertility dramatically. Significantly cooler nighttime temperatures will render the flower completely sterile, and the flowers will drop from the plant unfertilized. The ideal nighttime temperature range to encourage optimum fertilization is between 60 and 70 degrees.
Humidity can affect pollination's success as well. Low humidity dries out the pollen and makes it too powdery for fertilization. High humidity causes the pollen to become sticky and unable to move for pollination to occur.
Tomato plants grown in a greenhouse setting require vibration to transfer the pollen on the flower since there is no wind within the confines of the structure. This can be achieved with a softly blowing fan. There are also battery powered pollinators available that are designed specifically to help tomato flowers pollinate successfully. Commercial greenhouse growers pollinate every second day, according to the University of Florida.
Some commercial greenhouse operations use bumblebees for pollination, according to the University of Florida IFAS. The bees are specifically bred and cultured for the task of pollination. Each hives ability to pollinate lasts 6 to 10 weeks before replacement with a new hive becomes necessary. The life-span of the bumblebee runs approximately 14 to 25 days, according to the Discover Life in America Organization. Only the queen bumblebee lives through the progressive seasons to begin another hive. This makes purchase and rotation of new hives essential for a commercial tomato greenhouses to maintain constant ongoing tomato plant pollination.
Catface--misshapen or scarred--tomatoes result when fertilization of the ovule is incomplete. The situation is not a disease but a genetic occurrence at the time of pollination.