• Milkweed attracts Monarch butterfliesEric Bean/Photodisc/Getty Images
  
  Plants can typically survive one or two days of flooding, but an extended period will damage the root system of susceptible plants by depriving them of oxygen. Areas of the garden located in frequent floodplains require plant varieties that can withstand flooding. Gardens planted along rivers, waterways, streams and ponds are also susceptible to rising water levels, so only plant varieties that withstand a water-logged root system.
  
  

Yellow Flag

• The yellow flag (Iris pseudacorus) grows to a height of 3 to 5 feet and produces a wealth of greenish-gray strap-like leaves. A herbaceous perennial, the plant begins producing flower stalks that tower up to 4 feet and contain 4 to 12 flowers during the spring and summer months. Each brilliant yellow flower measures 3 to 4 inches apart. A few cultivars exist that produce flower stalks that stand 8 feet tall. Cultivars that produce white flowers and variegated foliage are also available.
  
  The plant is highly flood tolerant and will survive full submersion, a wet root system for a prolonged time and drought-like conditions. Plant the yellow flag in full sunlight for the best flower results. It can quickly colonize an area through a rhizome root system and self seeding. Consider removing the seedpods to prevent the seeds from becoming widely broadcast throughout the garden. Yellow flag grows best in fertile soil. The plant grows best in U.S. Department of Agriculture zones 4 to 9.
  
  

New England Aster

• The New England aster (Aster novae-angliae) thrives in a wide range of conditions from dry to wet, according to the Environmental Protection Agency's website. The plant quickly naturalizes in the garden and puts on a wildflower display. Carefree and easy to maintain, the New England aster grows to a height of 3 to 6 feet and produces daisy-like purple or pink flowers with an orange center. The plant blooms in the mid to late summer months and into fall. It always draws a wide range of butterflies and bees to the garden. Cultivars that produce pink blossoms are also widely available commercially.
  
  Plant the New England aster in an area of the garden with full sunlight for the best flower display.
  
  

Swamp Milkweed

• The perennial swamp milkweed (Asclepias incarnata) grows to a height of 2 to 4 feet. It produces pink flower clusters from July to October, and the flower stems can tower 5 feet in height. Swamp milkweed, which produces a milky sap, thrives in wetlands, swamps and in moist areas of the garden and will withstand flooding well. The swamp milkweed is a food source of the Monarch butterfly caterpillars, according to the University of Texas at Austin's website. Following flowering the plant produces brown, long seedpods that add wintertime interest to the plant.
  
  Plant in full sunlight or partial shade. The plant prefers fertile acidic soil but will grow well in heavy clay soils.