I am wanting to root my rhizomatous begone that was given to me Monday. It was planted in a heavy dirt. It was wilting so I removed it this morning. Here are some pictures of what I have. Right now I have it in water.
Cut off the big leaves since they are doomed on the plant as is. You can save the leaves for rooting as well. Cut the stems to about an inch from the leaf surface.
A tray or small pot with a quality potting mix or perlite will be your best bet. Wiggle the cut rhizomes into the mix much like a bearded iris with the rhizome (root side) making good contact with the potting mix. Water in and place in a shaded area. If indoors you may need to cover the pot or tray with clear plastic to keep humidity high.
Do the same thing with the cut off leaves by pushing the stem of the cut leaf into the same media.
Another method I've started using this year are the Jiffy pellets. They work fairly quickly but I have reservations about the mesh liner.