• Greenhouse Plant Pollination

    One challenge of raising flowering-fruiting crops in an enclosed environment is that there are no natural pollinators to assist in pollinating the crops. Without adequate pollination our crop production can be substantially diminished.

    Aquaponic systems that focus on leafy lettuce and herb production need not worry about this problem, but those who grow fruiting crops must take this into consideration if they want to maximize their fruit production.

    My own aquaponic system and greenhouse includes a variety of fruiting crops, from tomatoes, cucumbers, bell peppers, and strawberries to avacodos, lemons, limes, oranges, grapefruits and other tropical trees. Production is always increased when I pay attention to pollination.

    Commercial greenhouse tomato operations often use vibrating rods that are held against the stem of each flowering cluster to cause the cluster to vibrate rapidly, knocking the pollen from the anther to the stigma where it travels down to the ovaries and a new fruit develops. Without pollination no fruit develops and the flower falls off.

    In the out-of-doors, bees perform essential services as community pollinators. Surprisingly it is not the gathering of pollen that does the most good, but the vibrating of their wing muscles while in contact with the flowers, while gathering pollen that causes the greatest pollination.

    In a greenhouse environment there are many ways to accomplish this essential task. Some of the methods I have used include:
    1. Commercial pollinating devices (glorified electric toothbrushes), daily usage on all open flower clusters.
    2. Electric toothbrushes, daily or twice daily vibration of the flower clusters.
    3. Planting self-pollinating varieties. (many greenhouse cucumber varieties are self pollinating, as well as some tomato varieties).
    4. Paint brushes (brushing open flowers day and night)
    5. Flicking the support strings on the tomato plants. (vibrating the flowers and causing pollination).
    6. In my greenhouse, the air circulation fans, heater, and cooling fans all cause vibration and air movement which helps in pollination. Also the support strings are attached to the greenhouse frame and outside wind vibrates the frame. For my own home production this has provided good production of tomatoes, but doesn't help with the citrus trees.
    7. Bumblebee's
    Greenhouse Bumblebee Pollination
    The recent addition of bumblebees is a first for my greenhouse. They are used commercially and are very effective. Unlike honeybees, bumblebees work longer hours, visiting more flowers in the same time period and live in smaller hives and in smaller numbers. Natupol supplies mini hives with 1 queen and a dozen worker bumblebees. The bumblebees are docile and non-aggressive.

    I recently purchased a class C hive from Hydro Gardens who is a supplier for Natupol a brand of Koppert Biological Systems. The first hive came damaged as the cap on the bee nectar tank was left off and the hive and bees were all sticky. With no questions asked, they supplied a replacement hive, which arrived in good condition.

    The cardboard box lid comes off and there is a plastic cage filling about 2/3 of the box. The bumblebees are in the cage, which is filled with what looks like a cotton batting. The bottom portion if the box is filled with a collapsible bag full of nectar supplement. You remove the cap and the opening is plugged with a foam plug that gets moist with nectar mixture. The hive has 2 one way openings (in and out) and a plastic slide that either blocks both holes, opens one hole that allows bumblebees to get in or opens two holes that allows bumblebees in and out.

    The exit slot is covered with a mesh cloth that the bees chew through before they can get out and fly. This allows you to place the hive and let the bees settle down before they get out.

    The bumblebees emerged within 24 hours. They are busy moving about spreading pollen and pollinating the many flowers in the greenhouse. They do not seem to take notice of me as I water, prune and work in the greenhouse.

    A class C hive is said to last 4-5 weeks and can cover a 4-5000 square foot area. The bees are Bombus Impatiens (Eastern) Bumblebees. For a small hobby greenhouse the cost is prohibitive (approx $85.00 plus shipping). I'll be interested to see how long the hive does last. I like the idea of allowing the bumblebees to do the work.

    I'll report later, on the effectiveness of bumblebees for the production of mixed verities in a hobby aquaponic-greenhouse system.
    Comments 2 Comments
    1. nwestwood's Avatar
      It's been over 4 weeks. I see a noticable difference in fruit set on all my citrus trees and the avacado trees. Additionally the bell peppers have set a lot more fruit. I don't presently have tomato plants in a fruiting stage, but will in another month or so.

      One danger are the greenhouse fans. I've wrapped my overhead air circulation fan with fine mesh wire and covered my exhaust fan outlet with screen as well. One to prevent bumble bees from getting sucked into the fan and killed and the other to keep them from being sucked out of the greenhouse all together. At the 4 week mark, the hive is strong with both young and old bees at work. I'll report in another month on how they are doing.
    1. nwestwood's Avatar
      The hives stayed strong for about 4 months, then I began to see a decline in active bee's and by 5 months there was no activity.