Floating plants—such as water hyacinth, water lettuce, and duckweed—drift freely on the water’s surface, shading the water to help control algae.
Submerged plants, also called oxygenators, provide food and cover for fish and help control algae. They can float on the water’s surface, or you can plant them in pots so the roots sink to the bottom. Examples include hornwort, Canadian pondweed, and Cabomba.
Marginal plants, or bog plants, grow best in containers placed in shallow areas of the pond or in very moist soil at the pond’s edge. Plants such as cardinal flower and water iris have showy flowers.
Deep-water plants root in soil, and their leaves and long stems float on th¬e surface. Plants such as tropical water lily, lotus, and yellow pondlily provide contrast with floating leaves, upright spikes, and interesting flowers.