Begonias are perennials, and bloom again and again from the same set of tubers, or root formations. Many begonias are warm-weather plants, though, and require indoor storage during the cold winter. The plants also require good moisture, loose foundations, and some specific spacing during planting and replanting.
Begonias require quick-draining sites, and will suffer and rot in standing water. Raised beds, quick-draining soil and compost all work well for these plants, which also grow successfully in peat moss, ground bark and manure. Begonias do best in partial shade and dappled sunlight.
According to the University of Wisconsin Extension Service, begonias started as seeds can grow within inches of each other, in shallow growing trays. Once the seeds germinate and begin to grow, each plant should get a 4-inch pot to itself.
Spacing: Outdoor Tubers
Once plants have established tubers and are ready to be put outside they require more space. Plant begonia tubers in a loose foundation 8 to 12 inches apart, with indented or sprouting side up, to give the plants room to grow. Don't cover the tubers; their upper ends should stick up out of the soil after planting.
Spacing: Potted Tubers
In pots, grow begonias closer together for decorative effect. Fill flower beds or large pots with a mixture of quick-draining soil and compost, and plant begonia tubers 3 to 5 inches apart. Water potted begonias more often, since they'll dry more quickly than garden begonias.
After planting, water the begonia tubers with an inch of water and monitor their growth. Roots and sprouts will start within weeks, and may become crowded. If you have a tuber that puts up multiple shoots, cut away all but one to decrease crowding in the area.