Regional Gardening Reports :: National Gardening Association

In the Garden:
Coastal and Tropical South
April, 2008
Regional Report

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Cypress knees (in foreground) and elephant ears (on opposite bank), are both marginal plants that thrive at the water's edge.

Plants on the Edge

Many gardeners have a water feature in the landscape, and many more of them would like to have one. A pond or water garden opens up a whole new range of planting possibilities. But after you install the water lilies, don't forget the plants that line the pond. Many of them are as functional as they are beautiful.

Both floaters, such as water lettuce, and submerged pots of waterlilies help keep the water clear and free of excessive algae growth. The recommendation is to cover one-third of the surface with plants. Likewise, surrounding one third of the water feature with marginal plants works to ground the design and lift the spirits.

Marginal plants are those that can grow in wet sites on the edge of the pond and its immediate surrounds. Some waterside favorites, like cypress trees, will grow in dry soils but they won't have their best-known features -- cypress knees. Others, such as elephant ears, will multiply rapidly when their roots reach into the water below their crowns, unlike their less rampant habits in drier soils.

Plants suitable for use as marginal plants include cannas, flag iris, Louisiana iris, papyrus, and native spider lilies. They send their roots into the soil at the edge of the pond and often push through it into the water below. Their roots help keep the soil in place and filter runoff into the pond, which reduces silt flow into the water. Where pond liners or rigid forms form a barrier to roots, marginal plants still have a role. Their leaves ease the transition visually and help cover the black plastic edges.

Living Inspiration
Plan to line one-third of the pond with marginal plants. If you line the western edge, the shadows cast by the setting sun on the plants will dance on the water and soothe your soul as you sit by the pond late in the day. If you line the eastern edge, the shadows may shade you! Psychologists attribute the calming influence of a pond to the sound of the water; designers cite the soaring effect of upright plants reaching from the pond to the sky. Either way, we benefit.

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