Tuberous begonias

[vanozzi]

Just pricked out these tuberous begonia seedlings.They were all hand pollinated, quick to germinate, but slow to then get moving. Maybe I have about 500, 300 pricked out, 200 to go.
Any other tuberous begonia freaks out there?

[Leon]

Paul,
I can't seem to grasp the idea of cross pollinating tuberous begonias.  The flowers seem to be very fragile and somewhat enclosed.  Are most of the tuberous begonias fertile?   How did you accomplish the hand pollinating.  Have you grown begonias from seed before?  Are the seed the size of dust?  The concept sounds interesting.   I would really like to hear more about this.   

[vanozzi]

G'day Leon -- To answer your questions require a a bit of a long winded reply in order to entice you into giving it a try.
Yes, I've grown tuberous begonias from seed before, however this was about 16 years ago when I had a property in the Dandenong Ranges in Victoria , Australia.

Infertile or not? Well as the modern hybrids are derived from several of the smaller South American tuberous begonia species, you will encounter some fertilization problems, as those species have different chromosome numbers.I don't have any records of the chromosome count on any of the modern hybrids, but just make your considered crosses and you should get some seed.This past season, I made 12 crosses, pods looked good with seed, but only 5 lots germinated.My most hopeful cross is Saturn (F) x Midas (M), but as with all breeding, they may turn out duds.

Last year I used mainly English cultivars from  Blackmore and Langdon and this year I have added another 18 cultivars, some of which are the finest that Ralph Willsmore (Australia's main breeder of tuberous begonias),has released.

Breeding-- Usually there is one large (double) male flower with a (single) female flower on either side of it.If unsure, you can identify the female flower easily as it has a distinct ovary pod behind the petals.It will be 3 winged.
The biggest problem is a lack of pollen,which, when available, is well hidden on most cultivars, and quite sparse. It may not be on well defined anthers. Use a small soft pollinating brush and gently place what is available on the well defined stigma (on the single flowers). If the cross is successful , the petals fall off the female flower within a few days, the pod swells and starts to point downwards.It will be ripe when it begins to split in 6 to 8 weeks.

Sowing--the seed is indeed like dust, so take care not to sneeze or cough in it's direction !
In Australia, sow late June, early July in shallow seed pans  about 3cm deep with sterilized soil, in a propagator set at 20c.
 (Brian Langdon  recommends 18c to 24c   for Jan/Feb sowing in the Northern hemisphere)
 I use 1 part peat moss to 2 parts seed raising mix. (recommended in Australia is 2 peat moss 1 sand 1 loam ) The peat should be sieved through fine mesh wire and after mixing and sterilizing, leveled flat. Water the seed tray from the bottom up in a water trough, but don't let the water overlap, as it will dig holes in the soil surface. As the seed is like dust, to get a good even distribution you can mix it with fine silver sterilized sand and using a sheet of paper, carefully spread it on the saturated surface ,Don't bury it or cover it, just let it sit on the surface of your soil mix.I then mist spray the soil, cover the tray with a plastic dome and place in the propagater. Others spread the seed and then water from the bottom, but if you miscalculate and water laps over the top, you will loose too much seed. You can cover the pan with a sheet of glass if you wish and position it in a well lit but shaded position.Don't let the soil dry out.Within  about 8 days , using a magnifying glass, you will see tiny green specks.It will take longer if you have no heat.Prick out seedlings when their leaf is about half cm.Be careful as they are delicate. I use cell packs of either 100 or 64 at this stage, as there is less disturbance when they are potted up again. Brian Langdon says ''after germination,temperature is less critical, min 13c.''
I also used several different pollinators to a stigma, but recorded all.
Good luck, its quite easy and the seedlings can be flowered in their first year.
Hope I haven't muddled it too much 

[Leon]

Oh no! I feel another obsession coming on. 
I actually have not had good luck trying to grow plants from dust size seeds but this does sound like a fun project. 

[brianw]

I grow a Begonia boliviensis form, and have only ever propagated it from cuttings. Quite easy if done early enough in the summer to get a small "bulb" established before winter. This is so prolific with seed the dust covers things below. (It is in a window box) Is there a reason I never have any selfsown? The box is protected and more or less frost free over winter but must have lots of seed on the surface. There is just 1 small plant not obviously where I planted it but over 4 years or so I can't be sure how it got there. The main plants have stems 2 cm or more thick by end of summer. I only cut it back last week. At RHS Rosemoor they used to have it in the garden next to Lady Anne's house but I don't know if it overwinters there.

[vanozzi]

Hello Brian -- Begonia boliviensis makes a fine show and certainly is prolific with pollen and seed.There is no need to hand pollinate this specie , but it helps. My plant covered the window sill with
 ''seed dust''.

I would suggest that you aren't getting any self sown seedlings appearing at the base of your plant due to lack of constant moist soil, incorrect temperature and humidity.If the soil dries, the tiny seedlings die.Try scattering some seed in late winter/early spring in a small seed punnet with already saturated soil, enclose in a plastic bag and place in a warm spot.
Boliviensis seems quite easy to germinate.I only swept the dust from my window sill into a small punnet and placed it in the orchid house.It germinated and the seedlings are growing well now.

Boliviensis was used to create the basket varieties and as it has ample pollen, you may use it onto your standard varieties to create some interesting cascade types.So if you are interested in producing some standard seedling varieties of your own, but are having difficulty in locating any standard pollen, you can at least  produce ample seed of cascade types to keep your interest up.

I'm fortunate that I have an expert amateur grower not 30 klms from me, so have access to his knowledge and friendship.

[Paul T]

Wow, Paul.  Great work.  I have a few tuberous begonias, and would have more if I could get their conditions right.  Those that I have taken care of and kept dry over winter are all dead, and those that were in small pots knocked onto their sides in my front yard are all growing just fine.  Frustrating, to put it mildly.  I'd love to grow more of them, but they are hard to find in anything other than basic colours unless you're investing large amounts into tubers that you hope survive the following winter.    I may have to try the hand pollinating as well, to try to get some more.