Most folks assume a conversation about “the birds and the bees” is one that involves a metaphor for reproduction or a description of a life cycle. Such an assumption is spot on. Although birds, butterflies and other animals have roles as pollinators, the bee is by far the most important creature responsible for the pollination of crops in the agricultural world.
Bees transfer pollen from one plant to another effortlessly (the dust sticks to their hairy bodies and legs as they fly around), and release pollen into the air by buzzing about. However, bees have their own life cycle that generally includes a period of dormancy over the winter, so they may not be locally available to perform their vital task as a pollinator in your hydroponic or controlled environment setup out of season. Under these circumstances, nature needs some help to facilitate the pollination of indoor crops. Fortunately, any of several methods can help ensure your plants get the pollen they need regardless of the harsh conditions outside.
Import some bees
A large greenhouse operator may choose to purchase or rent some honey or bumblebees. As long as they can be safely shipped, and your growing facility provides an environment conducive to their survival, they will acclimate to their new surroundings and accomplish their pollination roles. Bees should not be imported into an area where pesticides are used, as the same chemicals that keep aphids and mites at bay will damage hives.
Hand or mechanical pollination
Hand pollination, also known as mechanical or manual pollination, is a technique used to enable the transfer of pollen from the stamen of one plant to the pistil of another plant (cross-pollination) or to itself (self-pollination). If not pollinated sufficiently, a female flower or fruit set may fall off, not appear at all or will develop in a small, misshapen fashion.
Tomatoes contain male and female parts on the same flower, so they are considered self-pollinating and hermaphroditic. These are extremely easy to pollinate. Usually, all they need is some wind (a fan’s breeze) or a slight physical agitation to disperse the pollen. Agitation is performed by giving the plant a quick shake or by exposing it to vibrations. An “artificial bee” is a vibrator that mimics a bee’s activity by producing vibrations similar in frequency to a bee’s buzz. The best time to do this is when temperatures are warm and humidity is low, and the task should be repeated every couple days. Peppers and eggplants will respond to these manual methods as well.
Strawberries are also considered hermaphroditic. The flowers are about an inch across and contain white petals and a yellow center. The stamens in a strawberry are composed of a filament and an anther. To pollinate, we need to transfer the pollen from the stamens to the center of the flower. We can manually transfer the pollen by lightly rubbing the flowers together. Generally, the largest berries are the ones that were most heavily pollinated.
Some plants are self-pollinating but are not hermaphroditic. These plants contain separate male and female flowers on the same plant, but not on each flower. Therefore, they need some additional help to pollinate.
On smaller flowers, a cotton swab or paintbrush may be used to gently transfer pollen from the male to the female flower. Simply dip the brush into the center of the male blossom (stamen) and transfer the pollen dust to the center of a female flower by swirling or dabbing the brush around the stigma. If the flowers are big, simply cut off a male flower, remove the petals and use the remaining part (stamen) to contact the stigmas of the female flowers. Crops in this category include squash, zucchinis, cantaloupes, cucumbers, watermelons and pumpkins.
When growing zucchinis, the male flowers will have a plain stem under the flower, be shorter than female flowers and may appear in clusters. Female flowers will have a tiny fruit or vegetable where the stem meets the flower and are longer. Generally, a plant will contain more male than female flowers.
No pollination necessary
Other plants do not need to pollinate. These include carrots, beets, broccoli, leafy greens, root veggies, celery, onions and most herbs.
In large operations where hand pollination is not economical, the use of a pollination spray (blossom set spray) may be helpful. The sprays contain cytokinins, or naturally occurring hormones that trigger the growth of a tomato ovary. The spray is applied to newly opened blossoms until runoff. Despite its name, it does not pollinate anything, but rather causes the development of tomatoes without pollination. Resulting seeds from a crop that has been artificially pollinated should never be planted.
Controlled pollination (cross-pollination)
Sometimes we wish to maintain control of the pollination process or avoid it altogether. For example, if we are growing several varieties of heirloom tomatoes in close proximity to one another, we may want to ensure no cross-pollination occurs between plants to maintain the genetics of each strain. Pollination bags are often placed over the plant canopy to keep isolated from pollen. If we wish to intentionally cross-breed strains, remove the clear bag and use the brush method or rub the flowers together to create a fertilized hybrid. A hybrid fruit will contain a combination of the genetic traits of both the parent plants (pollen contributor and flower provider). The seeds will result in a new hybrid strain, if planted.