Hand-pollination is a technique used to pollinate plants when natural or open pollination is either undesirable or insufficient. It involves the manual transfer of pollen from the stamen of a male flower to the stigma of a female flower. This can be done either by removing the petals of a male flower to expose its stamen, which will then be brushed against the receptive stigma of a female blossom in order to deposit the pollen; or by using a small brush or swab. The female flower is then closed to prevent any pollen contamination from external sources. Besides its simplicity, hand-pollination helps to keep control of cross-pollination between varieties grown together.
In commercial breeding operations, this method is commonly used to create intentional crosses and produce hybrids seeds. It is a laborious process–as it frequently involve the emasculation of flowers–that is often delocalized in regions where labor is inexpensive. For the garden seed saver, hand-pollination will mainly be used with monoecious plants, especially members of the Cucurbitaceae family as well as corn to prevent cross-pollination and therefore maintain the genetic purity of a variety.
For some self-pollinated crops such as tomatoes that require wind or buzzing insects (or conditions that mimic it) and where either of them is lacking (i.e.: in a greenhouse), each plant can be lightly shaken up to imitate a breeze or the vibration of certain bees and promote pollen shed. Flowers can also gently be tapped individually. Timing is key, as pollen shed normally occurs from morning to late afternoon, with midday being the ideal time for release and transfer (note that some pollen transfer can still occur in less than optimal weather). This technique–less tedious than using a brush–will ultimately assist the flowers in inducing the process of fertilization and improve fruit set.
Specific hand-pollination techniques for applicable crops are discussed in Section VII.