Tropaeolum polyphyllum

Tropaeolum species do make more tubers. I have grown some and when the plants are finished and died down for the season I dig up the tubers. I often find several more - some smaller and some larger.

In Norway T. polyphyllum do overwinter outside planted deeply and with stones in the soil (for warmer soil) and with drainage.

I finally got some good seeds from Goteborg Botanic Garden and Chileflora on eBay.  I gave them three weeks of warm, then a few months of cold.  The Chileflora seeds took two years to germinate.  They make very long taproots right away, so you should give them a deep pot.

The bands are 5" x 5" x 12" from Anderson Die in Portland, OR.  
http://www.andersonpots.com/prod-bands.html
They come in crates of 45.  If anyone wants some, I can buy a crate and break it up into smaller orders.  But I need to get requests for close to 45.

The plants behind the Tropaeolums are Echium wildpreti, which also make long taproots.  They look bad because they were in small pots over the winter, and I let them get too dry.

This is what they look like up close:

Note that I planted them in their original band, which you can see poking just above the soil.  They don't make a firm rootball, so I didn't want to take them out of the smaller band.  I'll remove the smaller band when the plants go dormant.

Ah ha!  I was wondering where to get "band pots", so thank you very much for posting that link!  Actually, I didn't even know what they were called... they have a plastic cross on the bottom, right?  I made a futile attempt to find a supplier last year - it's great to know where I could get more.

Yes, the Anderson bands have the plastic cross at the bottom.