Plant Profile

Alluring Aquatic Plants

Written and photographed by Carole Ottesen

A large garden pool at Wave Hill in New York is planted with variegated iris, tall water canna (Thalia), the puckered, two-toned leaves of elephant ear (Taro), a miniature cattail, and small, shocking pink water lilies. Behind the pond is a pot of flax (Phormium) and a clump of porcupine grass (Miscanthus sinensis ‘Strictus’).

There is a dizzying range and number of aquatic plants. The fact that the average garden pond will accomodate only four or five of them is the downside of water gardening. To narrow down the choices, it helps to select a mixture of floating plants and marginals. The mixture should “cover one-third of the pond’s surface” for optimal pond health and beauty, recommends Mark Simpson of East Coast Landscaping.

Floating plants, such as water lilies, grow submerged, but send up leaves and flowers to float on the surface. Marginal aquatics, such as papyrus or iris, grow in saturated soils in very shallow water or pond margins. “You can set pots of marginals on top of upturned clay pots,” says Dave Sollway of Johnson’s Florist and Garden Centers, to give them the shallow depth they require.

Floating plants have a horizontal effect and help to shade and cool the water; among their legions are hardy ones that survive the winter and tropical types that don’t. They are further divided into day and night bloomers. Marginal aquatics tend to be upright plants that take up less of the water’s surface. Vertical in effect, they are often used as backgrounds and edging.

Water Lily Nymphaea

Among the hundreds of water lilies, all floating plants, there are a number of dwarf-to-medium types that are ideal for limited space. One such is ’Laydekeri Rose’ with miniature pink blooms and grass green leaves. It will spread to about three square feet. ‘Laydekeri Rose’ is an excellent choice for a small pond or a tub garden.

Site: Requires six to eight hours of direct sun.

TLC: Maintain 8-12 inches of water over the crown. “Pull off the leaves,” says Tim Guy of Merrifield Garden Center, and “drop the lilies into the deep part of the pond for the winter.”

Tropical Water Lily Nymphaea spp

“Tropical lilies are much better than hardy ones,” thinks Guy. They begin to bloom after temperatures reach 80 degrees or more “and continue until Halloween,” he adds. Day bloomers open their flowers at about 9 a.m. and stay open until about 4 p.m. Night-blooming tropicals open their flowers as the sun goes down and stay open into the next day. Both are fragrant, hold their blossoms above the water, and continue to bloom into October. A good day-blooming tropical is ‘Marian Strawn’ with eight inch, fragrant flowers and purple speckled leaves.

Site: Tropical water lilies require six hours of direct sun.

TLC: Wait until daytime temperatures reach 70 degrees before setting plants out. Maintain between 8 and 18 inches of water over the plants.

Japanese Water Iris Iris ensata

‘Ise’ and ‘Eleanor Perry’

Japanese water irises are spectacular May-to-June blooming marginal aquatics. Choose named cultivars for the biggest and best flowers. The two outstanding forms shown here are lavender and purple ‘Ise’ and magenta flowered ‘Eleanor Perry.’

Site: I.ensata require sun and “like to grow right in the bog,” says James White of Merrifield Garden Center. Keep the surface of the pots just at water level.

TLC: Lift pots, but keep moist over winter. Feed in spring and divide every three or four years.

Dwarf Papyrus Cyperus haspans (syn. isocladus)

Dwarf papyrus is a marginal aquatic with umbrella-shaped leaves. It is a great sculptural addition to a shady pond, but will also tolerate sun. Bring the plant into the house to live as a houseplant over the winter.

Site: Dwarf papyrus grows well in sun or shade. Position container just under the water.

TLC: Overwinter indoors with constant moisture.

Pickerel Weed Pontaderia cordata

When native pickerel weed’s leaves emerge in spring, they are tightly curled and present a striking vertical appearance. After the heart-shaped leaves unfurl, blue flower spikes are produced from June until November. When grown in containers, the leaf and flower bouquets form neat accents that rise two to four feet above the water’s surface. Pickerel weed, a classic marginal, is also an excellent pond edger.

Site: Grow pickerel weed in part to full sun under two to four inches of water in containers.

TLC: Divide or start seed in saturate soil in early spring. Pickerel weed can overwinter in place.

Canna Canna ‘Praetoria’

Cannas, better known as tender garden perennials, double as marginal aquatics and respond to the consistent moisture of a pond by reaching six feet. ‘Praetoria’s’ spectacular variegated leaves glow in the sun and outshine the orange flowers that develop in late summer and early autumn.

Site: These flourish in sun to part shade.

TLC: Raise canna’s container to roughly even with or about one inch under the water surface. The ideal temperature for winter storage of canna rhizomes is 50-60 degrees.