Swamp Milkweed grows about 2'¾"-4' in my garden, and begins blooming in late June.  It also comes in pink and pinkish-purple, too.  You do not need a swamp to grow this in!  It will grow in ordinary garden soil.  Unlike some other milkweeds, swamp milkweed doesn't have a long tap root, and can be moved easily.  Monarch butterfly caterpillars feed on this plant.