Most of the beautifully foliaged Rex begonias are rhizomatous, that is, they have a thick stem or rhizome from which the leaves, flowers, and roots grow. The rhizome creeps on top of the soil, not through it.
These begonias have extremely shallow roots and do best in azalea-type pots.
No direct sun for these it fades the stunning foliage colors. Usually, rhizomatous begonias stop growing during winter's short days; a few even lose their foliage and appear to be dead. They all become active again in early spring.