Plants for ponds need to be able to withstand pooling water. These pond plants are hardy enough to take standing water and can be full water plants that can take growing in deep water or marginal water plants that are good for the borders of ponds where the water isn't too deep.
Yellow flag, Iris pseudacorus, is from the iris family and can be called yellow iris or water flag. It is an easy-to-grow and fast-growing perennial water plant. Stems can get up to 8 feet tall with grayish green leaves 3 to 5 feet long. Flowers are yellow, 3 to 4 inches wide, and bloom profusely. Grow a yellow flag in full sun in water or moist soils. Propagate via division or seed. It is hardy in USDA hardiness zones of 4 to 9.
Pickerelweed, Pontederia cordata, is from the pickerel weed family. Leaves are arrowhead-like and 4 to 8 inches wide and in a basal clump. They will get 3 feet tall. Flowers are on 6 to 8 inch spires and violet blue, blooming from spring to summer. Grow pickerelweed in full to filtered sun in moist soil or in ponds toward the edge, no deeper than 6 inches. Propagate via division. It is hardy in USDA hardiness zones of 5 to 11.
Alligator bonnet, Nymphaea odorata, is from the water lily family. It is a fragrant perennial water plant. Flowers are white with a center that is yellow, 4 to 9 inches wide, blooming through summer. Leaves are 4 to 5 inches wide and float. The whole plant gets 4 to 6 feet tall. It will be dormant in the winter. Grow alligator bonnet in full sun in water or any soil. Propagate via rhizome division. It is hardy in USDA hardiness zones of 3 to 11.
American lotus, Nelumbo lutea, is from the lotus family. It is a perennial water plant. Leaves can float and are bluish green. Flowers are yellow and 10 inches wide. Seed pods will look like showerheads. Grow American lotus in full sun. Propagate via seed or rhizome division. It is hardy in USDA hardiness zones of 4 to 11.
Umbrella sedge, Cyperus involucratus, is from the sedge family. It is also known as umbrella plant or galingale. It is an evergreen, easy-to-grow perennial water plant that is fast growing as well. It can get 2 to 6 feet tall. Leaves are basal and at the bottom of the stems. Small greenish flowers are in clusters that will give way to dark brown fruits. It grows in shallow water or good garden soil in sun or shade. Propagate via clump division or rooting one of the "umbrellas." It is hardy to USDA hardiness zones of 8 to 11.