How do I stunt a begonia boliviensis without killing it?

This will be it's third year. Last year it was about 4ft in all directions!
I had to shove it in a corner as it was taking over the patio. I'm not sure I've got a big enough corner if it gets any bigger.
I'd be afraid to cut it. How about really tired, spent compost?I
Maybe they don't get any bigger - that's the answer I would prefer

 

I've not grown one, but if it's in a pot that will presumably limit its size. I would still give it nice compost though, on the basis that big and healthy looking is better than big and sickly.

 

True. @ViewAhead

 

Looking it up it's a tuberous begonia, if so, I would have dried it off before winter and restarted the tuber into growth this spring, or is that what you are doing and the tuber is getting bigger.

If so, when it shoots in spring you can cut the tuber up with new shoots on each piece, just dust the cut surface with sulphur and let it callous over before replanting.

 

Yes @pete that's what I've been doing but I'm a bit nervous about chopping it up.

 

Well I can't think of much else you can do, maybe remove a couple of shoots at tuber level when new growth starts, but it might just look a bit thin then for a while.

 

If you cut it into several bits, then you could plant 3 divisions in a single pot which would bulk it up. Then plant the rest into other pots.

I Googled how to split and it said -

AI Overview


Splitting
Begonia boliviensis is best done in early spring as tubers start growing, by cutting the tuber into sections using a sterile knife. Each division must have at least one growing point (eye), and should be allowed to dry for 2–3 days to prevent rot before potting in well-draining, moist soil.
Step-by-Step Guide to Splitting

• Timing: Spring is ideal, when the tuber is starting to produce new growth.
• Divide the Tuber: Using a sterilized sharp knife, divide the tuber, ensuring each piece has at least one "eye" or sprout.
• Dry the Cuttings: Let the cut sections sit in a cool, dry place for 1–3 days to callus and prevent infection.
• Potting: Place the divided tubers in potting mix with the concave (crater) side facing upward, and the top of the tuber just below the surface.
• Aftercare: Place in a warm, sunny spot
  and water carefully, avoiding direct watering on the crown to prevent rot

There's also a YouTube vid of how to do it -


Good luck!

 

I've just potted up the mahoosive begonia . The tuber/ corm(?) is the size of a pasta bowl and covered in buds. This does not bode well

 

If it's too big, can't you cut it up, dust the cut surfaces with sulphur, and then distribute the spares to unsuspecting friends?

 

I suppose so but I wouldn't dare in case I kill it. @CarolineL

 

Sorry I just noticed others had suggested the same!

But when the sprouts get bigger, you could cut a couple off and try rooting them - like with dahlias.

 

Chelsea chop.

 

I did root a broken bit in water last year but 'forgot' to bring it in for the winter.

 

4ft ?!??? Pictures please of this Audrey III! If needs be, give it your entire garden!

 

Here it is early July last year. Not reached its full powers by then. @micearguers