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Home > Seed Starting

Growing Begonias from Seed
by Brad Thompson

Growing begonias from seed can seem like something that only commercial growers and experts can do.  Let me assure you that itís possible for anyone to grow seed. The chapter below will show you the methods that I have used for years with very good results. They arenít the only methods but have been successful for me.  They will be for you also, if you havenít already developed good methods of your own. If youíre successful already; then continue with what youíre doing; donít mess with a good thing If you are having problems, this chapter just may help you though. 

It really isnít complicated, but does require reasonably sterile conditions, some dexterity and a lot of patience. In return, you get to watch little miracles happen. If you follow the steps I outline below, you should have no trouble growing seed into mature plants. Iíll also try to outline problems that you may run into and my solutions. I start planting seed in September or October when the weather is cool and stop planting in January so that all of the seedlings will hopefully be large enough to go outside in April or May. However, seed can be started any time of the year. 

What You Need 


First of all, you need some good seed but that really goes without saying.  At the end of this chapter you will find directions for setting your own seed.  There are many sources for seed, many commercial companies have at least a few varieties of begonia seed.  If youíre an American Begonia Society member, the best source for buying seed is through their seed fund.  Seed is sometimes the easiest way to acquire new species of begonias.


The most important thing you must have to be successful with seed is to have a fluorescent light setup to grow them under. You could conceivably start the seed on a windowsill.  You usually wonít be successful growing seed without a light setup unless, of course, you have your own greenhouse.  

Seedlings require a great deal of even bright light in order to form compact robust seedlings and you wonít get that on a windowsill. Youíll get leggy one-sided seedlings that wonít transplant well and will probably not be strong enough to make it to maturity. Under artificial light they receive constant light from straight overhead so you wonít end up with those scraggly leaners like you would in a window. As far as the artificial light goes, you donít need some fancy elaborate light stand.  You can make your own with just a simple cheap shop light, hung wherever you have the room. You donít need expensive bulbs either.  I use whatever is on sale, usually cool white bulbs, which will work fine. Those grow-lights may be better but not enough better to justify the expense, especially when you have to replace them every six or eight months.

Potting Mix

For a mix to start seed in I use one part peat moss (or Sunshine #3), with a third #2 (small) perlite. You donít have to be real particular because you could probably go with equal parts of each if you wanted with no trouble.  Sunshine #3 is a commercial peat based mix that also contains polymers as a wetting agent.  It isnít much different than peat moss except that it absorbs and holds water more easily.  There are many similar peat based mixes that are popular in different areas of the country.  Some growers lightly cover the top of the mix with finely ground vermiculite.  I have also successfully grown seed in Miracle Groô potting mix.  It is more course however and it already contains fertilizer so donít add fertilizer when planting the seed.


When planting the seed, I use one quarter strength fertilizer. I use Miracle-Gro ô but you can use any fertilizer with roughly equal numbers. I also put in a few drops of Superthrive ô (vitamin B-l) just for a little extra help. I donít know for sure if it makes any difference to the plants but I feel better. Iíve used it for so long that I really canít remember what a difference it made when I first started using it, but it must have been good.  The main reason I use Miracle-Gro ô is because it also contains trace elements but nowadays most fertilizers do.


I plant my seed either in 1 1/2 inch pots or take condiment cups and put holes in the bottom to make my own pots.  Either works just as well as the other. Some people use shallow trays but they take up too much space under lights if youíre planting very many varieties at one time.  After theyíre planted, I put the pots in a small clear plastic shoebox with a clear lid on top. Any small, clear container with a clear lid will work as long as it doesnít have air holes in it.  The purpose of starting the seed in enclosed containers is too keep the humidity up, keep the conditions sterile, and to keep the potting mix from drying out.

What to Do


 You need to sterilize the container that youíre going to put the pots of seed into (the shoebox).  I sterilize my containers with a hot water and bleach solution.  There are many anti-bacterial products you can use for this but bleach is effective and cheap.  I allow the container to soak for a half-hour or so to make sure itís done its work.  Wear gloves when working with a bleach solution.  A ten percent bleach solution should be strong enough.  You should also sterilize all the pots youíre going to be using to start the seed in at the same time.  Allow them to dry before using.  Condiment cups should already be sterile.

Preparing the Pots

Fill your pots with the prepared potting mix and pack it down gently in your little pots almost to the rim.  Allow a quarter of an inch or so for watering.  Prepare the fertilizer water using hot distilled or boiled water and use it to soak all of your little pots of soil.  I set the pots in a tray and fill the tray with the water about an inch deep.  I let them sit in the water for awhile. This has two benefits. One is the hot water will soak into the peat moss better so will thoroughly wet it and will also sterilize your soil mix somewhat at the same time.  Most commercially bagged mixes should be relatively sterile already if kept sealed between usage.  Make sure you use pots that wonít melt in boiling water. I leave them soaking in the water until after all of the pots are planted, taking each one out, planting it then putting it back to make sure the seed on the surface gets wet also.  Make sure the mix has cooled somewhat before using for planting. 

Planting the Seed

To plant the seed, first make a label with the name of what you are planting and the date. Put the label in the pot before you plant it.  Since begonia seed is so fine, itís hard to keep track of which ones are planted if you donít put the labels in first.  Pre-labeling will save you lots of trouble in the long run.

 Plant the seed by emptying the package onto a clean sheet of typing paper.  Using the paper, allow the seed to roll off onto the surface of the mix.  Make sure you do your planting away from the other pots youíre planting.  The seed is so small you could end up with some of it in nearby pots if you arenít careful. Let maybe 50 or a hundred seeds roll off.  If you donít have good vision, youíll just have to wing it.  Hopefully, youíll see that something is rolling off and be able to guess when youíve planted enough.  If you plant less seed, they may not come up well.

 Begonia seeds seem to prefer company and germinate and grow best will many in the pot.  From my experience if you only have a few seeds in the pot they donít thrive as well.  If you plant too many seeds, youíll have trouble separating them.  Donít cover the seed, begonia seed needs light to germinate. Use a spray bottle to lightly mist the surface of the pots after planting to make sure the seed makes good contact with the medium.  I usually use the same fertilizer water in the spray bottle that I initially used to wet the mix. 

After you have planted all of your little pots.  Again, seedlings seem to like company so try to have a container that is shallow and plant enough little pots to reasonably fill it. Thatís why a plastic shoe box works so well, itís shallow and only fits 10 to 15 little pots at a time, which is a reasonable number to work with for each planting. After all of the little pots are filled and labeled, I take them out of the tray of water and put them on newspaper for a couple of minutes to drain.  I then place them into the shoe box and under the lights.  I usually line the shoebox with several thicknesses of newspaper or paper towel.  This will help collect any moisture that forms on the sides of the box and distribute it evenly.  Otherwise the water may collect in one end of the box so a couple pots will be sitting in water.

 I keep the lights 6 inches or less from the top of the box and try to run them for at least 14 hours a day. I have left them on 24 hours a day with good results however.  You may be more energy conscious.  The seedlings vary in sprouting time depending on the variety and the age of the seed.  They can come up in as quickly as 4 days or not for a month. I have heard it reported that some varieties take months to germinate.  I guess I will never grow any of those because if nothing comes up in a month or so, I remove the pot and count it as a loss.  How long you decide to give them is up to personal choice.  If you have the room, you can give them longer.

Potential Problems

Drying Out

 f the surface of your mix dries out you can rewet the mix by misting with a spray bottle.  You can also put the pots in water in water to soak, leaving them until the surface of the mix is damp again.  No, do not use boiling water this time.  Normally the pots will stay damp without any additional rewetting or spraying but this does happen occasionally.  Sometimes too much bottom heat will make them dry out faster than they would ordinarily.  The humidity provided by the box is usually enough to keep them damp till the seedlings are ready for transplanting.


If you see a slimy black or greenish substance on the surface of the soil, you have an algae problem.  Either the seed had spores in it or you didnít sterilize well enough. You can save any seedlings that look like they are in danger of being smothered by transplanting them right away.  It is a delicate procedure when they are that small especially if you lack dexterity. They really donít have any problem with the transfer as long as you got them out with some roots attached.  Sometimes, moss spores grow and these will smother out the seedlings if you donít transplant them right away because it grows faster than the seedlings.  There are products that can be used to kill algae such as Physanô but I donít have experience with using those products.

Damping off

This disease shows as seedlings that die off or seedlings that seem to start growing but then rot and fall over.  It can be caused by several reasons but the main three are that your mix is too wet, you didnít sterilize properly, or you donít have enough warmth.  Make sure the pots you plant the seed in has drainage holes.  This will keep the mix from staying overly wet.  Seedlings need warmth to grow so can damp off if not kept warm enough.  Just as will mature begonias, seedlings donít like dampness combined with cold. Another possible cause is that you donít have enough light.  Seedlings that are stretching and reaching for the light are weaker and more prone to damping off type problems.  There are fungicides you can use if you already have damping off.  You may have to test whatever product you use first to see that it works and doesnít damage begonia seedlings.  I havenít found that to be a problem.  I have used most products that worked on mature begonias on seedlings also with no damage.  Itís always best to test first however.

Tall and Leggy Seedlings

If your seedlings appear to be tall and leggy, you donít have your lights close enough to the containers or are not leaving them on for enough hours.  As stated before seedlings donít grow well on windowsills.  You should be growing them under artificial light unless you have a greenhouse. 


 When to Transplant 

Although seedlings can be transplanted just as soon as they come up, it is best to wait for them to get larger before transplanting unless you are experienced.  When the seedlings first emerge, they have only a pair of equal sized leaves.  These are the seedling leaves and nourish the plantlet until it has formed enough roots to support itself.  The seedlings at this point have only one little root trying to work its way into the soil. 

Within a week or so after the plantlet comes up, it starts to form its first true leaf. (If you have ever looked at a begonia plant , you will notice that it puts outs one alternating leaf at a time unlike some other plants which put them out in pairs.)  When this first leaf is out and is about a half an inch around itís the proper size for transplanting. The reason for this is that it has now reached the stage where it has formed some roots but not so many roots that you wonít be able to separate the little plantlets.

I separate the little plantlets by grabbing the one true leaf and gently using it to pull the plantlet out of the mix.  Of course, you will ruin some but you will have plenty regardless.  If your mix is too hard and the seedlings donít come out easily you can use a knife tip to break up the soil a little first.  As long as your seedling has a root or two after you pull it out it will be fine.  I usually only transplant about 25 or so out of the pot at a time and save the remaining ones in case anything goes wrong with the first batch.  The ones left in the pot will not grow much because they quickly run out of food.  However, in the humidity of the sweater box they will sit there in suspended animation for a long time - sometimes up to a year.  If they dry out soak the pots to rewet, donít overhead water.

What to pot them in

Transplant the seedlings into the same conditions you are removing them from. Use the same soil-less mix such as peat and perlite, or Sunshine #3 and perlite.  Keep them in a sweater box or clear covered container, at least until the next transplanting.  You can either put the mix in shallow trays and transplant the seedlings in little rows or you can use regular seedling trays cut to fit your container which have separate little compartments for each seedling.  The ones I use have individual 1/2 inch squares for each seedling and seem to work very well.  I have used sandwich boxes cut in half and put four or five holes in the bottom for drainage.  These worked well too and are certainly easier to clean than the commercial seedling trays I use.   

I put a shallow layer of my mix in each tray and sterilize it by watering with the boiling hot water with fertilizer (light fertilizer, 1/4 strength) and let the trays of mix soak for a while to absorb the proper amount of water and to cool off.  After they have cooled a little, I set them on newspaper to drain, usually tipped slightly on edge so they drain easier.  I then take a pencil or pen and use the point to make little holes 1/4 inch deep or so, at regular spacing, about 1/2 inch apart for the seedlings to go into.  I also sterilize a sweater box for them to go into after theyíre planted, with a bleach and hot water solution After the sweater box is dry I put several layers of newspaper in the bottom. This will absorb any extra moisture from condensation  when you have the trays in it so they wonít be sitting in water.


Once you have everything prepared, get your pot of seedlings and immediately copy the label and put it in the tray youíre going to transplant into so you wonít forget to do it later.  No, you wonít remember what they were no matter how well intentioned you are, as I can swear to.  (As can Mary Sakamoto when sheís looked in one of my sweater boxes and said, ďOh what are these? There isnít a labelĒ, and I suddenly remember that I donít remember.)  Avoid the confusion and label first.

Pull up a seedling, as described above, and set it into the hole you made with the pencil. If it doesnít fit then make your holes a little bigger.  Repeat this process until youíve transplanted as many as you want.  Then go back with your pencil, or whatever your favorite utensil is, and smooth around any that need it.  They donít need much tamping around; if you made contact with the soil they will root and grow.  After planting, I give them a misting with the spray bottle as with the seed.  If you soaked the mix properly in the first place, they shouldnít need any further watering until they are ready for the next transplanting.

If any start to die or rot, you have the mix too wet or not sterile enough, so open the lid a crack to let it dry out some.  If that doesnít work and they are still dying off, as a last resort spray them with a fungicide to try and kill the fungus problem the too wet conditions created. Donít be discouraged if you have some failures. Count those as learning experiences and try again.

Where to go from there 

About a month or month and a half from that first transplanting they should have grown to fill the surface of the tray.  Itís time to move them up again.  At this stage they are running out of food and are becoming too crowded.  Theyíll either just sit there and not grow any more or theyíll get leggy and be hard to make into nice plants or to transplant. 

They should be ready to transplant into small 1 to 1 1/2 inch size pots at this time. You donít have to be quite as concerned at this stage about perfectly sterile conditions as in the earlier stages but your sweater box should be sterilized.  Fill your little pots with mix as when you planted the seed.  You can use a knife tip to make an opening in the mix to receive the little plant.  I use my mix dry, transplant the little plant and put the pots in a shallow tray filled with the cold or room temperature fertilizer water to soak. Make sure to label each pot as you go so you wonít miss any, or if only one type of seedlings are going in one sweater box you can just put in one label for the box and label them before you take them out. 

I usually move the plantlets out of the sweater box when they have grown to fill this size pot or after they have reached the next size pot.I put them under lights on stands that are totally covered in plastic to keep the humidity in.  I place the small pots on a shallow tray filled with a layer of perlite to soak up any water from watering the plants and also to raise the humidity.  Watering the perlite occasionally to keep it moist is necessary because the runoff from watering the little pots is not enough. After they have grown to fill these pots, you can treat them like regular plants. Lift the plastic cover gradually to harden them off and then transplant in your regular mix. If it is warm enough, you can move them outside in full shade for another couple of weeks and then start moving them into your regular growing areas.

Making and Collecting your own Begonia Seed

There are two types of begonia seed, hybrid seed and species seed.  Hybrid seed is seed that is created by pollinating one variety of begonia with the pollen from another variety of begonia.  Species seed comes from self pollinating wild species of begonias.  Only species will come true from seed.

There are also three types of pollination, self pollination, cross pollination, and open pollination.  Self pollination involves pollinating a begonia with its own pollen or the pollen from another begonia of the same species or variety.  Cross pollination involves using the pollen from an different variety to pollinate.  The seedlings that result from cross pollination are call hybrids.  Open pollination is when a begonia is pollinated without human help either by insects or the wind. 

If your desire is to produce seed of species, either for yourself or to share that species with others, you must self pollinate the species.  If you only have one plant of the species, itís acceptable to use the pollen of that plant to pollinate itís own female flowers.  However, for genetic diversity, itís better to gather pollen from another plant of the same species for the pollination.  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 back up in case you lose a parent plant.   

If your desire is to produce hybrid begonia seed, all of the methods are acceptable.  Hand pollinating yourself is preferred however.  Any seed removed from a hybrid plant is hybrid seed, whether self, cross, or open pollinated.  Most hybrids can only be reproduced using cuttings except for a few strains of semperflorens and tuberous hybrids.  You canít self pollinate a hybrid such as B.í Irene Nussí, collect the seed and grow more B. ĎIrene Nuss' begonias from it.  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 either donít produce pollen because theyíre sterile or the flowers fall off without opening.  On others the pollen just doesnít mature before the flower falls off. It wonít 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 that donít have complete flowers.  Those wonít have pollen either, like B. ĎQuestion Markí that doesnít have any anthers.  Any true specie however has to have pollen, thatís the only way it can reproduce itself in the wild.  If a species begonia doesnít have pollen itís a cultural problem.  A change in something youíre doing like overwatering, humidity, etc., may get it to produce pollen, if it wasnít.

On begonias, the male flowers are the flowers that have no ovaries behind the petals.  They usually have four or petals and a cluster of anthers in the middle.  The easiest way to test for pollen is to take a mature male flower thatís 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. 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 itís warm and dry.

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.  I usually choose a cluster that has several female flowers that are ready.  On begonias, the female flowers have a winged ovary behind the petals.

I usually take three or more male flowers that I know have pollen off of the father plant for the pollinating.  On the mother plant I take the cluster that Iím going to pollinate and remove any male flowers (so it canít self pollinate) even from other close clusters.  On species it is wise to keep all male flowers removed in advance of crossing it because the wind can cause it to self pollinate.  I also remove any immature female flowers from the cluster.  They take away energy from the ones youíre pollinating and you wonít have to remember that there were some in that cluster you didnít pollinate. 

To do the pollinating, take the male flower and gently bend the petals back, as a handle, to fully expose the anthers and gently brush it in the center of the female flower. As I said, I use three or more males and with these I brush across all the female flowers in the cluster just to make sure all get pollinated.  To mark the cross (this is extremely important) I 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 doesnít 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 donít close by the second day, then reapply pollen to make sure the pollination is successful.  The petals donít always close on all varieties, so it may still have taken even if they donít 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 wonít get any more sustenance when the stems have shriveled so you canít hurt anything by taking them off.  Donít take them off before this time.  They wonít have matured to their full potential.  If youíre in doubt leave the pods on till theyíre 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 plastic film canisters, medicine bottle, or something similar to finish drying.Donít put a cover on because you need to make sure they get fully dry and donít 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 donít 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 donít roll easily so rolling isnít a hundred percent method.  To be absolutely sure about seed that doesnít roll you can examine it under a cheap microscope.  Most good seed looks like popcorn kernels under magnification.  For comparison, you can look at seed that you know is good so you can see what it should look like.  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 made for stamps.  Most regular envelopes however arenít air tight enough to contain the begonia seed since itís so small.  Write the seed information on the outside with the date.  Since I donít plant seed until late fall, I just keep them in a coffee can or box until planting time.  In the winter when Iím done with all the planting Iím going to do that season I store the remaining seed in the refrigerator.  You need to use a moisture resistant container to store the seed, such as a Tupperware container, when storing long term in the fridge.  Begonia seed will last for many years in the refrigerator.  I know Iíve had seed that was viable ten years later.

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