Growing begonias from seed may seem like something that only commercial growers and experts can do, but it is not. In fact, it is something the Society would like to see everyone succeed with! Whether you are collecting species for conservation, or hybridizing seed to bring something new to the table, learning about seed and germination is the place to start.
One thing you will find is that every person does things slightly differently. It is like cooking, everyone has a different recipe. So, we’ll describe the basics, and you can read further to capture more information. If you’re successful already, though, then continue with what you’re doing; don’t mess with a good thing.
It really isn’t complicated, but does require reasonably sterile conditions, some dexterity, and a lot of patience. In return, you get to watch little miracles happen. What you need are the basics: seed, soil, water, warmth, and light. Once things have begun to sprout and grow, you’ll want some fertilizer.
The key difference between Begonia seeds and many other types of seed is how tiny the seeds are. Raw Begonia seed looks like rusty dust, so a little seed goes a long way because there are many tiny seeds in what appears to be a small amount of dust. Because these seeds are so small, it changes a couple things about how to plant and grow them.
- Because the seed is tiny, you do not cover the seed with a potting mix, or anything, in fact. The tiny seedlings need light right away, and even a very fine covering can keep the seed from growing.
- Because the seed is small, there is very little stored food in each seed, so it is best if you provide a low concentration of plant food immediately after the seeds sprout, to keep them growing strongly.
- When the seed is very small, it is easily affected by changes in humidity, so you need to keep the sown seed in a sealed container until the seedlings are big enough to tolerate a bit more open air..
Be ready, because even marginal success usually means a lot of seedlings to transplant and grow and so it is always best to start small and see what you can handle before finding yourself afloat in tiny begonias!
Making Your Own Begonia Seed
There are three types of pollination:
- Self pollination involves pollinating a Begonia plant with its own pollen.
- Cross pollination involves using the pollen from a different plant to pollinate.
- Open pollination is when a Begonia is pollinated without human help either by insects or the wind.
There are two types of Begonia seed, hybrid seed and species seed.
Goal: To make new and different hybrid begonias, and every seedling will look different, showing unique characteristics.
Parents: Pod (female flower) and pollen (male flower) parents from very different backgrounds, selected for ornamental traits.
Seedlings: Because each seedling had a different mix of DNA, every seedling will be somewhat different.
Goal: To create more seed of the same species, every seedling should look the same.
Parents: Pod (female flower) and pollen (male flower) parents are from the same species.
Seedlings: Because all seedlings came from the same species, each seed will recreate that parent species.
Making species Begonia seed
Many species of begonias are rare or endangered both in the wild and in cultivation. If you own species of begonias, you should make every attempt to self pollinate all of them to help keep them in cultivation. This seed can be shared with friends, with seed funds, or as backup in case you lose a parent plant.
If your desire is to produce seed of species, either for yourself or to share that species with others, you must always self pollinate the species. If you only have one plant of the species, it’s acceptable to use the pollen of that plant to pollinate its own female flowers. However, for genetic diversity, it’s better to gather pollen from another plant of the same species for the pollination. When you cross one species plant to another of the same species you do not get a hybrid and usually every seedling looks the same.
Making hybrid Begonia seed
If your desire is to produce hybrid Begonia seed, all of the pollination methods are acceptable but will give you different results. Hand pollinating is preferred, however, as if you use open pollinated seed, you can never say for sure who the pollen parent was. Any seed removed from a hybrid plant is hybrid seed, whether self, cross, or open pollinated.
Because their seedlings do not come up matching the parent, most hybrids can only be duplicated using cuttings. For example you can’t self pollinate a hybrid such as B.’ Irene Nuss’, collect the seed and grow more B. ‘Irene Nuss’ begonias from it, but you will get a whole lot of plants that are a bit like ‘Irene Nuss’ and a bit like the parents of that hybrid. Any seed produced by a hybrid will result in new hybrids and not recreations of the parent.
Unlike many other types of plants, begonias have separate male and female flowers. On most varieties, the males come out first in the flower cluster. As they fall off, the female flowers come out. There are a handful of exceptions.
Finding the Pollen
With begonias, especially hybrids, which parents you choose to pollinate with depends also on which ones you can find pollen on. Some hybrids don’t produce pollen either because they’re sterile or the flowers fall off without opening. On others the pollen just doesn’t mature before the flower falls off. It won’t take you too long to learn which ones never have pollen. There are also hybrids that were crosses between two very unrelated types of begonias and that don’t have complete flowers.
Any true species, however, has to have pollen; that’s the only way it can reproduce itself in the wild. If a species Begonia doesn’t have pollen it’s a cultural problem. A change in something you’re doing, such as overwatering, humidity, too much light, etc., may convince it to produce pollen, if it wasn’t already.
On begonias, the male flowers are the flowers that have no ovaries behind the petals. They usually have four petals and a cluster of anthers in the middle. The easiest way to test for pollen is to take a mature male flower that’s fully open. Hold it up to bright light and gently flick your fingernail across the anthers (the anthers are the yellow parts in the center of the flower). If there is pollen you should see a little puff of yellow dust flick out; it resembles smoke. If you have trouble seeing, try flicking the stamens across a piece of black paper and you should see the pollen on it. The best time to check is early afternoon when the pollen is more likely to be ready, because it’s warm and dry.
Remember that sometimes it is helpful to store, or share, pollen as well. If you want to build up stock of a given pollen, try pinching out the anthers with a fine pair of scissors or your fingernail into a small envelope. Keep them stored, very dry and cool. A sealed tupperware container in the refrigerator is best.
Choosing the Female Flower
Female flowers are usually ready to pollinate when they have been open for a couple days and the petals are open to their fullest. Some varieties open fully with the petals curled slightly back but not all open fully. A good choice is a cluster that has several female flowers that are ready. On begonias, the female flowers have a winged ovary behind the petals.
Take three or more male flowers that you know have pollen from the father plant for the pollinating. On the mother plant, take the cluster you are going to pollinate and remove any male flowers (so it can’t self pollinate) even from other close clusters. On species, it is wise to keep all male flowers removed in advance of crossing, because the wind can cause it to self pollinate. You may also want to remove any immature female flowers from the cluster. They take away energy from the ones you’re pollinating and this way you won’t have to remember that there were some in that cluster that you didn’t pollinate.
To do the pollinating, take the male flower and gently bend the petals back, as a handle, to fully expose the anthers. Then gently brush it in the center of the female flower. As suggested, use three or more males and with these, brush across all the female flowers in the cluster just to make sure all get pollinated. To mark the cross (this is extremely important) use a narrow strip of mailing or computer label with the cross written on it and bend it across the flower stem. Use a pencil to write on the label so it doesn’t wash off.
If your pollination was successful, in the next day or so, the petals on the females will close and eventually drop off. If they don’t close by the second day, then reapply pollen to make sure the pollination is successful. The petals don’t always close on all varieties, so it may still have taken even if they don’t close. A sure sign is the ovaries start to grow fatter. This shows something is happening in there.
Harvesting the Seed
It will take a month or so for the pods to ripen, so be patient. Some varieties may take a lot longer, but a month is normally the time period for the majority of begonias. When the flower stems dry up or shrivel, you can remove the pods, whether they are dry or not. They won’t get any more sustenance when the stems have shriveled, so you can’t hurt anything by taking them off. Don’t take them off before this time. They won’t have matured to their full potential. If you’re in doubt, leave the pods on till they’re fully dry. Make sure you watch them and take them as soon as you see the pods start to split or you may lose all of your seed though.
After collecting them, place the mature pods into small paper envelopes, you need to make sure they get fully dry and don’t rot. Leave them for at least a week or more to be sure. If you have pods that fell off just when you thought they were almost ready, you can try drying them. They usually don’t have good seed, but you may get lucky. Make sure you label the container with the cross to keep track of what that seed is.
Cleaning and Packaging the Seed
Open the pods on a sheet of typing paper. To separate the good seed from the chaff, tilt the paper slightly to roll the good seed off onto another piece of paper. The chaff and immature seed is left behind. If nothing rolls, then it probably is all chaff and not good seed. There are some Begonia seeds that are oddly shaped or so small they don’t roll easily, so rolling isn’t a hundred percent method. To be absolutely sure about seed that doesn’t roll, you can examine it under a cheap microscope or jewelers loupe. Most good, viable seed looks plump under magnification. Bad seed looks shriveled, cracked or distorted under the microscope. If still in doubt, seek out an expert if there is one in your area.
Fold the cleaned seed into a small piece of paper and tape it closed. You can also use small envelopes such as those made for stamps. Most regular envelopes, however, aren’t air tight enough to contain the Begonia seed, since it’s so small. Write the seed information on the outside, including the date. If you plan to start them later, store the seed in the refrigerator. You need to use a moisture resistant container, such as a Tupperware container, when storing long term in the fridge. Begonia seed will last for many years in the refrigerator. Some are known to be viable ten years later.
Learn More about Growing from Seed