Fruiting plants are hands-down some of the most satisfying plants to grow indoors as well in a greenhouse. There is an incredible amount of pleasure from picking a bright red strawberry against the backdrop of a typical March snowstorm here in Ontario. Whether it be strawberries, peppers, tomatoes, or even cucumbers, there is the added step of pollination that is required to cultivate a productive crop. This is because these are what we refer to as fruiting crops, not because they are what the average consumer would call fruit, but because fruit is how they are described botanically.
In botany, a fruit is the mature ovary of a plants reproductive system, which normally contains the seeds and other associated parts of the plant reproductive system. To grow a fruit, there needs to be the combination of pollen and a stigma to produce seed, comparable to animal reproduction. Though this may not be the most appealing way to think of fruit production, it certainly is an important if not crucial aspect to be considered by a grower.
For fruit to be successfully pollinated, pollen from anthers (the male component of a flower) must be released and then meet the stigma (the female part of a flower). If the pollen is successfully placed, it will grow a pollen tube down the stigma and through the style (the stem the stigma is located on) and reach an egg within the young ovary of the female portion of the flower. If this all happens successfully, the flower is now pollinated, and the ovary will begin to become what we know as fruit! This is straight forward for most fruiting crops but becomes especially interesting with strawberries, which are considered in some cases a “false fruit” or what we would rather refer to as an “aggregate fruit” due to their seeds being on the exterior and each seed representing a fruit structure that has been pollinated.
This is a little easier to see on other aggregate fruits such as raspberries and blackberries which clearly show individual ovary structures around each fruit. Because of this, botanically speaking a strawberry is not a berry at all (berries are defined as simple fruits that come from an individual flower and contain a single ovary).
So, what does all this mean for a strawberry flower during pollination? To a grower it means that to grow strawberries effectively not only one individual stigma needs to be pollinated like with a true berry or a composite fruit such as a tomato or pepper. Instead, each stigma needs to individually receive pollen to successfully form a uniform fruit. If you have ever looked at pollen on a flower you will see it looks like a bit of dust, but there are over 250,000 pollen grains on each strawberry flower, of which half are viable to pollinate the over 200 stigmas on a strawberry flower.
You would think this is a relatively easy task given the quantities of pollen available on each plant. For the most part this is correct, especially given that strawberries are self-fertile (some crops, such as apples require a completely different plants pollen to properly pollinate). However if each of the stigma are not successfully pollinated in a similar timeframe you end up with misshapen fruit from uneven ovary development.
This is where our friend the bee comes in! Bees are excellent pollinators and can make very efficient work of transferring pollen from flower to flower (which boosts success rates) and the frequency at which they vibrate releases pollen fast and places it within the stigma with ease. Our pollinator of choice is the bumblebee or Bombus terrestris who can ensure that each flower gets visited 15 or so times immediately after opening to ensure complete and thorough pollination.
So how do we get bees to pollinate our strawberries indoors or in an enclosed environment like a greenhouse? This is where insect breeding companies like Koppert or Biobest come in. These companies have developed an impressive distribution system to breed these bees in captivity and send pollination hives all around the world safely and effectively to help growers optimize yields and ensure quality.
This is an important network because it limits disruption to native pollinators and interference with the native population of pollinators by supplying clean, disease free, and healthy pollinators to indoor environments independent of outdoor conditions. These hives are kept in the indoor environment for a period (usually several months) and then are replaced with a fresh hive to keep the crop healthy and productive.
In conclusion, bees are a necessity to fruiting crops in indoor and greenhouse production systems. In an industry where nearly every aspect can be replaced with either a synthetic or automated technology solution, there is yet to be a replacement bees which have evolved with flowers for thousands of years to create the perfect relationship between nature and food production. This reinforces both the importance of pollinators indoors as well as in nature, and that we must continue researching the biology of bees and the effect of our practices on bee health.
For more info on hives, or strawberry pollination please check out some of our sources below at NC State Extension or BioBest Group: