Gardening Articles: Landscaping :: Container Gardening & Ponds

The Water Garden (page 4 of 4)

by Robert Smaus

Hardy Water Lilies

These plants are hardy from USDA Hardiness Zones 3 to 11, but whether you must move them indoors depends on the pond or container they're planted in and the extremes of cold in your area. In very cold-winter regions, you must take in hardy lilies growing in small tubs; store them in a garage or basement.

In milder cold regions, a de-icer that you float in the water and plug into an electric outlet will keep the water from freezing. You must take in lilies grown in containers in small inground water gardens also. Cover them with wet newspaper to keep them moist while dormant.

These lilies survive in natural outdoor ponds if the crowns and rhizomes are not in frozen earth under the ice in winter. The flowers, stems, and leaves die back, but the rhizomes remain alive. Find out the extreme maximum ice depth in your area. If your pond is deeper than that, your plants are probably safe. If you're not sure, take them in.

These lilies come in wonderful shades of pink, white, red, and yellow. During a season, the tuber will creep from one side of the pot to the other and, if the pot is too small, grow right over the edge. To contain them, repot when the weather warms in spring.

Hardy water lilies must be repotted every spring in a process that's similar to potting them up initially. With a serrated knife, saw off several inches of the growing end (the end with the leaves). Also, trim back roots so you end up with a block of root-filled soil about 8 inches square. The old soil will have turned jet black. It stains everything, so quickly wash spills off paving and other surfaces.

In a container wide enough to allow room for the roots to spread, plug any drainage holes with two layers of newspaper. Then plant the chunk of roots and leaves in ordinary garden soil at one edge of the container so that it can grow across the container. All water lilies need fertilizer at planting time and later in the season. Little tablets specifically for aquatic plants are the easiest to work with if you follow label directions.

After water lilies, my favorite additions to the water garden are (in order of preference):

Yellow snowflake (Nymphoides cristatum). Flowers on this aquatic plant are frilled like a snowflake. Its leaves are like a lily's but extensively marbled with green and burgundy. It's considered hardy from zones 6 to 10. In cold-winter areas, protect it as you would tropicals.

Water poppy (Hydrocleys nymphoides). This aquatic also has floating leaves, and it's adorned with clear yellow poppy flowers. North of zone 8, it's grown as an annual. Though quite hardy in my garden, it nearly disappears during the winter, like most aquatics.

Water hawthorn, also called Cape pondweed (Aponogeton distachyus). In my zone 10 climate, this aquatic takes the water poppy's place in winter. Its floating leaves are long and narrow. The white vanilla-scented flowers are floating racemes (flower spikes) that bloom in winter. The whole plant vanishes below water in summer and reappears in autumn. In cold climates, this plant blooms only in summer.

Parrot's feather (Myriophyllum aquatica). This reasonably well-behaved aquatic has feathery green foliage that floats on the surface between the lilies in my pond. The "feathers" stand about 6 inches above the water and add vertical form to the pond. If I let them, they would take over, so I hack away at them through the season.

Floating Plants. All of the above aquatic plants grow with roots submerged and tops floating on the water, but some aquatics actually float, roots and all, like little boats. You could call these "nautical" plants. The lavender-blue-flowered water hyacinth (Eichornia crassipes) is the best known but is far too weedy in my zone, quickly forming an armada. I like the gray-green leaves of water lettuce (Pistia stratiodes), another boatlike floater, and the tiny fronds of Azolla filiculoides, a fern that happens to float.

Submerged Plants. A few plants, called oxygenators, grow completely submerged. Supposedly they add oxygen to the water for the fish but actually they absorb extra nutrients that might increase algae levels. I grow only the fluffy fanwort (Cabomba caroliniana), and must remove lots of it every few weeks because it grows very fast.

Bog Denizens. Bog plants grow with their roots just under the water's surface. I've planted water irises, azure pickerel weed (Pontederia cordata), and the tall and stately red-stemmed thalia (Thalia dealbata). I have even added cannas, which do better in the pond than they do in my garden. All have quickly overgrown, so now I stick to the well-behaved water lilies and their friends.

Robert Smaus is the garden editor of the Los Angeles Times and has been the West Coast host of PBS's "Victory Garden."

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