Pollination and setting of tomatoes

In commercial greenhouses growers use bumble bees to pollinate their crops. If your plants are outdoors, there should be enough wind and insect activity for pollination. In the greenhouse, it is a good idea to gently shake the strings or other supports around mid day, or tap the trusses which have flowers open. If the weather is very hot and dry, it may help to water the paths in order to increase the humidity and cool the greenhouse.