Pollination Basics

Pollination basics can be improved by growers in their operations. What came first: the chicken or the egg? I cannot answer this question. However, in my experiences with hydroponic and greenhouse food crops, I can confidently tell you that before there are tomatoes, peppers, eggplants, strawberries or any other type of fruit there are flowers. Purposeful flower pollination is essential for most of our fruiting crops grown in controlled environment. While there are certainly many factors that effect fruit growth and development, pollination is paramount because it is necessary precursor to fruit.

Pollination Basics: Requirements;

If you are producing leafy crops such as lettuces, herbs or other specialty leafy greens you do not need to worry about pollination, only foliage, not fruits, are harvested and sold. Not all fruiting crops require pollination either. Though field cucumber used for hydroponic production such as the long Dutch or beit alpha types do not require pollination because these fruits are parthenocarpic; these fruits are formed without any pollination resulting in seedless fruits.

While bees may be used to increase the degree of pollination and to improve pepper fruit quality, they can also cause damage by visiting the flower too much and cause unmarketable fruit if managed improperly.

Pollination Basics: The Process;

All products of high-wire vining crops are fruits. In a culinary and (Horti-) cultural sense we consider peppers, cucumbers and eggplants vegetables. In a botanical sense, they are fruits. Fruits are the product of a successful pollination. For the ovaries to grow and develop into fruits, viable pollen mut be transferred from an anther to a receptive stigma. If the pollination is successful, the ovary enlarges into the different fruits that we harvest.

How do you know when a flower is ready for pollination? When a flower starts to open, it is not yet ready for pollination. The pollen is not mature and dehiscing from anthers, and stigmas are not receptive to pollen. As the flower continues to open, the pollen and stigma mature. As the pollen matures, you will see the anthers change their appearance to light greenish yellow with a smooth appearance to a bright yellow surface that appears rough because pollen is starting to shed. Petals are another good indicator of pollination. When the flower petals are fully open the petals reflex back, and this is an easy indicator of a receptive flower.

In addition to having flowers which are physiologically ready for pollination, you also want to have a greenhouse environment that is conducive for pollination. Temperatures below the lower 60s or above the upper 80s degrees are not conducive to pollen growth and subsequent pollination. Additionally, dry greenhouses are problematic for pollination and relative humidity should be maintained around 70%.

Possible Pollinators;

Now that you know which crops require pollination and are familiar with the pollination process, lets focus on how to approach pollination in your facility. There are a number of different pollination methods including by hand, with bees or chemically. Flowers can be pollinated by hand in different ways. It can be common to try and transfer pollen from the anther to the stigma by hand when pollinating a small number of plants, but this is a time consuming task. Thankfully, if the environment is favorable and the pollen is mature the flower simply needs to be shaken to release a “puff” of pollen that will reach the stigmas and pollinate flowers.

Bumblebees are the most common method used for pollinating greenhouse food crops, as they are an extremely effective and efficient method to pollinate large. There is a chemical approach to pollinating some crops such as tomatoes. Auxin, the plant hormone most widely known for its use to promote root growth on cuttings, can be applied as a foliar spray to promote tomato flower pollination.

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