What Is the Care for a Marginal Plant?

About

• Marginal plants, sometimes called bog plants, grow in shallow water on the perimeter of a pond or lake. The roots are in the water, but the body of the plant grows out and above the water. Marginal plants soften the edge of a water garden, giving a natural feel and help hide the pond liner. They also contribute to the health of the pond by decreasing light reaching the water, which reduces algae growth. They are hardy plants, easily cared for if planted properly and repotted periodically to contain growth.

Planting

• Marginal plants should be potted in a mesh planting basket. This keeps the plant contained, while allowing the roots to penetrate freely into the water. Use a heavy garden loam soil without the addition of peat moss or compost. Fill the basket halfway with soil, and pack firmly. Place the plant in the basket, with the crown of the plant about an inch below the basket lip. Fill in around the plant with soil, again packing firmly. Add 1 inch of gravel or stone to the surface of the soil. Position the plant in the shallow area of the pond, at the depth recommended for the specific plant variety.

Repotting

• Pond plants tend to grow aggressively and can quickly become too large for their pots, leading to plant decline or death. Repot overgrown marginal plants in the early spring. Gently remove the plant from its container, and rinse with a hose to remove soil. Look for the natural divisions between plant stalks or sections. You can carefully pull the plant apart at these points. Add soil to the planting basket, and replace a section or two of the plant to the basket so its crown is an inch below the lip of the basket. Add fertilizer formulated for water plants, then add more soil up to an inch below the plant crown. Fill the last inch with small pebbles to keep soil from washing away.

Tips

• Maintain your marginal plants by removing any dead, discolored or excessive leaves as needed. In winter, cut back hardy plants to 2 or 3 inches above the water surface. Hardy marginals that can survive northern winters include cattails, water irises and rushes. In cold winter areas, remove tropical marginals from the pond and over-winter inside, or treat them as annuals and replace each year. Tropical marginals include papyrus and cannas.