Bougainvilleas in planters can be overwintered in any frost-free place, even in the dark. A garage or a basement is ideal, but it must be frost free. Water only every three or four weeks, so the plant does not become completely parched. All the leaves will drop off, but the plant will remain dormant – and alive. In spring, move your bougainvillea to somewhere bright, but still frost free. A sun room is often ideal. Water more often, and as the first green shoots of growth begins, fertilize with a liquid bougainvillea feed. After the last frost, move your plant outside.