Friends on the island of Kauai, where we vacation every winter, inspired me to experiment with a container water garden last summer.
My three friends have very different potted ponds but their Zone 11 climate promotes lush foliage and year-round blooms for all of them. They all incorporate fish, everything from goldfish to tilapia to koi.
Chris' back yard is crowded with containers, from a small bowl on her patio table to large stock tanks overflowing with plants and filled with fish. Steven arranges his pots below his porch and screens them with a colorful arrangement of tropical foliage and flowers. Claire has several huge glazed pots in her sun-filled back yard, which she groups together artistically and surrounds with snowbush and hibiscus.
My attempt last summer to duplicate these tropical water gardens in Northern Minnesota's Zone 3 climate was less than a complete success.
I purchased a container 22 inches deep and 18 inches in diameter and filled it with lake water in late May. To support a potted canna and two pots of elephant ears (taro) at the back of the container, I arranged plastic pots upside-down on the bottom. I placed pots of bacopa and creeping Jenny to cascade over the edges. I floated water lettuce on the surface twice, but the roots rotted within a few days.
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I introduced three goldfish and two died within the first week. I added two more and one died. Two fish survived the entire season.
Champion containers
My mixed results made me wonder if anyone else was growing container water gardens in the Northland.
Pauline Erven, owner of Ponds of Plenty in Grand Rapids, said Sheila and Mariah Salo had several small container water gardens on their deck in rural Grand Rapids. Mariah, 16, is an active 4-H-er whose container water garden won a Reserve Champion ribbon at the Itasca County Fair in August. Her glazed pot combined Chinese lobelia, water lettuce, water hyacinth, water clover and chameleon plant.
"I had a lot of fun learning about water plants and what makes them grow," Mariah said, "but I had even more fun showing my creation at the fair and making people think."
Mariah uses Dechlor to de-chlorinate her water and Algae Clear to clarify it. During the winter, she keeps her container in a south window and turns on a grow light if the plants begin to yellow. If the water turns oily green, she drains most of it and refills the pot with fresh water. She uses a small chunk of Mosquito Dunk (a product made of dried Bacillus thuringiensis) once a month, and she never fertilizes during winter.
Erven suggests submerging pots about six inches below the water's surface; she uses rock or bricks to elevate them from the bottom. She also makes sure plants don't cover all of the water's surface. Among her favorite container plants are water clover, water hyacinths, mosaic plant, pennyworts and water lettuce.
"The most important thing to remember is that these plants do multiply, and you will need to prune them back," she said.
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Container water gardens are ideal for gardeners with limited space and a good way to try water gardening without committing to a more permanent pond, according to Erven. "And if you want to keep it, you can move it into the house and put it in a sunny window for the winter," she said.
From sand to water
Ann Fink of Duluth has experimented with container water gardens for 10 years. When her half whiskey barrels began deteriorating last year, she bought a used sandbox and installed a rubber liner. The large square water garden sits on her deck where she can listen to the soothing sound of flowing water and watch goldfish swimming among the foliage. Fink's water garden holds everything from water lilies, water cannas and Hawaiian white ginger to floaters like water lettuce and water hyacinths, the most productive plants she has grown.
"The hyacinths have gone crazy," Fink says.
Fink fertilizes her water lilies with a special formula for aquatic plants and overwinters them. Since they need a dormant period, she cuts off all the foliage, washes and dries them and stores them in vermiculite in a garage where the temperature never goes below 45.5 F. She leaves the cannas and ginger in a tray of water with a bubbler in a sunny window during the winter months.
Raccoons are her most serious problem. The nocturnal visitors once ate two large goldfish and left plants strewn about the deck. Another time the raccoons pulled the pump and filter out of the pond, causing the motor to burn up and nearly setting the house on fire.
Fink has learned not to clean her pond. "I've heard people say you need to let ponds develop their own ecosystems and it's true," she said. "It took me years to learn that the water is not going to be swimming pool clean."
Fink cleans the pump filter once a week, and she uses squares of barley straw to clarify the water. Because her pond is shallow and is exposed to full sun, she makes sure plants shade some of the surface to keep the fish cool and give them a place to hide.
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Season-long choices
Gretchen McDaniel orders and cares for water garden plants at Edelweiss Landscapes & Nursery in Duluth, and has sold several small container water gardens.
By trial and error, McDaniel has narrowed her choice of container water garden plants to those that stay looking nice all season. She believes taro is too sensitive to temperature and wind, so she only uses it in a very protected location. Water lettuce doesn't do well in full sun, and it, too, is very temperature-sensitive. Among her favorites are dwarf papyrus, parrot's feather, hydrocotyle, creeping jenny, thalia, bog arum, arrow arum, European brookline, corkscrew and spike rush, water hyacinth, sweet flag, water canna and miniature water lilies.
The rule of thumb is one inch of fish per one gallon of water.
"If you overdo it with the fish, you're going to have too much waste in the water," McDaniel says. Using a pump and a spitter (spouting ornament) generally solves the mosquito problem in containers.
McDaniel overwinters her water garden plants in three large liners. She suspends one grow light over the tubs, and she moves a small pump and spitter from one container to another each week, and sets a timer for 14 hours a day.
"Since the winter sun isn't as strong as the summer sun, I put these tubs in my best window and still use supplemental light,'' she says. She treats papyrus and umbrella palms as houseplants in the winter.
I'm already envisioning two container water gardens next summer. One will contain a single dwarf water lily and sit on our deck. In the other, maybe I'll try a small pump and spitter to keep the water moving, and I'll grow papyrus, thalia, hydrocotyle and corkscrew rush. My gardens might not be as lush as those on Kauai, but they'll be as close to tropical as northern Minnesota can get.
