Mirabilis jalapa: let the leaves turn yellow and brown, then cut themn off, dig them up, trim off the stubs, let the tubers dry a few days, and store in sawdust or peat in a cool place.

Mirabilis multiflora: let the leaves die off naturally, cut them off, leave the tubers in the soil, and put the pots in a sheltered corner outside so the soil doesn't freeze. In the colder areas, wrap the pots with bubble wrap to provide more insulation.