One of the biggest drawbacks to growing plants indoors is the lack of access to natural pollinators, like insects, birds or even the wind. For many houseplants, it won’t make much difference, but certain plants are going to need pollination in order to produce fruit or seeds.
Here’s how to handle it.
Before we get into the details and techniques, you should understand the reasons why pollination is necessary for some plants. Pollination is part of the reproductive cycle, and necessary for any plants to produce fruit or seeds as it brings together male and female cells.
So for your usual leafy or flowering houseplants, you can probably leave this chore alone and not worry about it. But for anyone who wants seeds to propagate their favorite plants, or is growing certain indoor vegetables (remember, “vegetables” like tomatoes or cucumbers are really botanical fruits), you have to allow for pollination or your plants will not produce anything.
A Little Botany
Before you start trying to hand-pollinate, you should be roughly familiar with the anatomy of a flower so you know what you’re aiming at. Without burdening you with botanical diagrams, you can easily recognize the basic parts. When you look inside a typical flower, you’ll see several delicate filaments. There should be one in the center, and several smaller ones around it. The center one is the stigma, the female part that leads to the ovaries inside the flower. The other ones are the stamens, where the male pollen is produced. The pollen itself is like a fine yellow dust or powder.
Technically, pollen (male) needs to be introduced to the ovary (female) of a flower, and that is consistent with all plants. Seems simple, but there is a bit of a catch. Not all plants have exactly the same pollination needs.
There are a few variations to these process. True self-fertile plants will produce flowers where the pollen can stay within the blossom and pollinate its own stigma. In these cases, there can even be pollination before the flower opens up at all.
For other plants, they are still self-fertile, but pollen needs to be moved from its source to another flower on the same plant. In all other cases, you will just need to transfer pollen from the flower of one plant, to another flower on a different plant, though it does need to still be the same species of plant. Trying to cross-pollinate between a geranium and a philodendron isn’t going to work.
There is one other situation, where plants produce completely separate male flowers and female flowers. Most indoor plants aren’t designed this way, but if you are growing some vegetables like squash or melons in a greenhouse, it could become an issue.
Hopefully, you’ve been able to follow this little botany lesson. The most common situation will be where the pollen needs to move from the flower on one plant, to a flower on another plant. You can focus on that as you learn more about hand-pollinating.
Once you have decided that your indoor plants need to be pollinated, the big question is how to go about it.
If you are dealing with self-fertile plants where the pollen can stay within a single male/female flower, like some varieties of tomatoes, the process is simple. For plants that are outside, it only takes a little breeze to shake up the flowers enough to knock the pollen around from the stamens and onto the stigma. But indoors, breezes may be hard to come by.
Gently shaking your plants may be enough as long as you are careful not to do any damage while you’re at it. Another way to shake-up the pollen is to use an electric toothbrush, placing it against the plant while running. The vibrations are strong enough to loosen up the pollen without really making much movement in the stems or leaves.
Here’s a quick demonstration of pollinating tomato plants by shaking:
For plants where you actually have to move pollen around, you’ll have to change tactics. The usual and most successful technique is to use a fine, soft paintbrush and gently dab the pollen from the stamen of one flower to the stigma of another. As I described earlier, you need to focus on moving the pollen to the central stalk inside the flower. If you are dealing with very small flowers, it’s almost impossible to miss. For larger blossoms, you do need to have a steady hand to target the stigma once you have your brush loaded with pollen.
Now, there can be another level to your pollination plans, if you want to make specific decisions about how your plants are bred. Combining the genes from two successful plants is the way to develop your own personal strain, to make plants with more flowers, bigger fruit or whatever traits you find the most appealing. On the other hand, you can also avoid using poorly performing plants in your breeding schedule to weed out weak genes.
Without becoming a genetic engineer, you can make a few notes about which plants you are cross-pollinating with others and keep some rough track of the results. Be realistic in your pollination goals though. You’re not going to create a magnificent new hybrid with just one cross-pollination between a couple of flowering houseplants.
An important point to remember is that trying to breed plants with a purpose will only have an effect on the resulting seeds, not the immediate fruit. Expect a few generations to pass before you start to notice any differences in your plants.
How can you tell if your efforts were successful? It will depend on the plant, but soon after you pollinate a flower, it will die back and drop its petals. Keep a close eye, and you should soon start to see a fruit start to develop at the base of the flower.
If the flower drops off with no further development, your pollination attempts didn’t take. While it’s disappointing that you’ll get no fruit or seeds from that flower, the plant itself won’t suffer for it and will continue to grow just fine until the next flowering cycle.
That is the basics of how to pollinate indoor plants, and hopefully you’ll have success taking on this new level of houseplant care.