Greenhouses are wonderful structures, aren’t they? These buildings can be small or massive, and allow all kinds of species to thrive in ideal conditions. Most tomatoes are grown in greenhouses, for example, and do well because they won’t be damaged by predators or hailstorms. But how do tomatoes pollinate in a greenhouse? These plants are pretty much dependent on flying insects or wind to fertilize one another. Both are basically nullified by greenhouse walls, right?
The answer might be a bit surprising.
Yes, tomatoes need either bugs or wind to be pollinated. And greenhouses are mostly devoid of both. “Mostly”.
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So, How do Tomatoes Pollinate in a Greenhouse? By Magic?
There could be some places where a small consortium of sorcerers sing pollination into action, but usually there are simpler methods.
For example, many greenhouses use bees.
You may be confused at this point, since bees generally can’t get into greenhouses. As such, how do they manage to pollinate those delicious tomato flowers? The answer is simple: they’re invited in. There are many places where you can buy bumble bees online specifically to introduce into greenhouses.
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“Why bumble bees specifically?” you may be asking. Well, it turns out that these bees work twice as fast as honey bees. Furthermore, bumbles have a more docile disposition than most other bees. They don’t swarm, and they’ll only sting a person when they feel really upset and provoked. In fact, they’re generally so chill that you really need to annoy or terrify a bumble bee in order to make it sting you.
A typical greenhouse hive will have 50 to 75 friendly little worker bumblebees, which will start pollinating the tomato flowers pretty much immediately. They just need to get their bearings first, and then they’ll get right to work. They’ll only live for about four to six weeks, unfortunately… but that’ll be just long enough to ensure that your crop is fertilized.
Tomato ovaries get the message to mature when they’re exposed to hormones known as cytokinins. If you hose down a bunch of tomato plants with artificial cytokinins as soon as their blossoms form, something startling happens.
Rather than being “pollinated” per se, the tomato flower ovules just start developing into mature fruits on their own. Yeah, that’s right: it’s not a question of artificial fertilization so much as tricking the flower into creating fruit spontaneously.
Interestingly, rather than being stunted or malformed because of the lack of pollen, these tomatoes tend to be quite large. The hormone-based fruiting trigger also seems to result in a more abundant harvest than those that have received actual pollen.
Pollinating by Hand
If you have fewer than 100 plants and you’re feeling really ambitious, you can pollinate your greenhouse tomatoes by hand. Basically, you just have to get creative with moving pollen from one part of the tomato flower to another. These plants are monoecious, which means that they have both male and female parts on the same flower. It also means that these flowers can pollinate themselves.
If you’re pollinating by hand, you’ll need to familiarize yourself with a flower’s reproductive parts. Yeehaw.
The male parts of the flower, known as the stamen (which consists of a filament and anther), produce pollen. The filament is like a stem, while the anther is the fuzzy bit that has the pollen actually on it. You’ll want to take a small paintbrush or cotton swab and transfer pollen from that anther to the stigma. This is the sticky, disc-like part of the female part (the pistil), which invites that pollen to stay.
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Once the pollen has been transferred, the flower is pretty much fertilized. The pollen grains will germinate into tubes, which trundle their way down to ovule land. Once Mr. Pollen Tube meets Ms. Ovule Egg Cell, a happy little plant embryo will develop. This is what will grow into a juicy tomato fruit that’ll be quite magnificent in sauce, salad, or gazpacho.
You’ll only have a short time to pollinate your flowers by hand. Flowers bloom and then die out within the span of a few days, so you have to move quickly. If all your tomato plants flower at the same time, you’ll have to invite some friends or other volunteers to help you spread that pollen around.
Now that you know the answer to “how do tomatoes pollinate in a greenhouse?”, you’ll know how to keep your own plants healthy! These same measures might not be needed if you’re growing plants inside your house, however. You may well get enough of a breeze getting through to disperse the pollen. Alternatively, just let some moths and bumble bees in the house so they can do their thing.
Either way, here’s hoping you have oodles of luscious tomatoes to enjoy this season!