Skip to Main navigation Skip to Left navigation Skip to Main content Skip to Footer

University of Minnesota Extension

Extension is almost done building a new website! Please take a sneak peek or read about our redesign process.

Extension > Garden > Yard and Garden > Container water gardening

Print Icon Email Icon Share Icon

Container water gardening

Beth R. Jarvis

Plant in pot

Container water garden.
Photo: Beth Jarvis

Water gardening adds a unique, new group of plants to home landscapes. Many, such as water lilies and water hyacinths, grow well in containers. Containers are an excellent way to sample the joys of water gardening before committing to a larger, permanent pond.

Locate your container garden so it can be seen easily from the house or serve as a focal point, drawing visitors into the garden. Consider the following when choosing a site for your water garden:

Most water plants require full sun for at least five hours. A spot that is shaded in mid- to late-afternoon is ideal. Three hours of direct light is minimum for water gardening, but it greatly limits both the number of plant choices and flower quantity and quality.

Falling tree leaves cause extra maintenance by clogging pumps and harming fish and plants. Keep your water garden away from overhanging tree branches.

Easy access to a water supply is important. Water that has evaporated from the container must be replaced to keep the water level constant.

Planting the garden
Any waterproof container that holds at least four gallons of water makes an excellent water garden. Some possible containers include a galvanized horse trough; a large, glazed pottery crock; an old claw-foot bathtub; or a whiskey barrel.

Plants will not overwinter in an above-ground container in our climate. Grow them in pots so they can be easily removed and stored for winter in a cool place where they won't freeze.

Put a layer of garden soil in the bottom of each pot. Set plants at the required planting depth, then fill the pots with soil. A top layer of sand or gravel about ¼-inch deep will hold the soil in place. Don't use a potting mix that contains perlite or vermiculite, which will float to the surface. Also, avoid any potting mixes which contain fertilizers or chemicals that may be harmful to aquatic life.

Saturate the soil by watering it thoroughly, then set the pots in the water garden container. Place bricks beneath pots to adjust planting depth for each species.

Line whiskey barrels with plastic, such as large, heavy- gauge garbage bags, since the wood may have absorbed something harmful to the plants and fish. A container the size of a whiskey barrel will provide room for only one water lily. Bog plants or grasses may be planted on the outer edges, depending on the container's size.

Because a water garden is a miniature ecosystem, the plants, water, sunlight and fish must interact together to thrive. If the water you use is chlorinated, let it sit for 24-48 hours to permit any chlorine to evaporate after the container is first filled. As water evaporates, replace it with chlorinated water from the tap; chlorinated water helps to control algae until the garden is balanced, usually 60 days. "Balanced" means that the plant and animal life will hold algae in check.

Many city water supplies have chloramine added, which is a more stable form of chlorine. If you use chloramine treated water, you will need to purchase a product to remove the chlorine. These are available from garden centers that sell water gardening supplies. Water added during the season to maintain the water level does not need to be treated.

The plants
Several types of plants are used in the water garden, including deep-water plants such as water lilies. Water lilies provide colorful, fragrant additions to a water garden. They prevent oxygen loss from the water surface and keep the water cooler. Tropical lilies are more fragrant, have larger blooms, bloom more frequently and come in more colors than hardy lilies. Plant them when temperatures reach 75° during the day and 65° at night. They will die when frost hits, so they need to be stored inside or treated as annuals.

Tropical water lilies require a foot of water over the crown. They need at least four hours of direct sunlight. Either late afternoon or early morning sun is adequate. Recommended varieties for a barrel garden include:

Hardy water lilies bloom longer in our climate, but alternate several weeks of "rest" with several weeks of bloom throughout the growing season. Plant them in 18 inches of water. Lotus is not recommended for above- ground containers. It needs 2-3 feet of water.

Submerged plants, also called oxygenators, are commonly used in large water gardens to clean the water by absorbing excess nutrients, slowing algae growth, and replenishing the oxygen supply. For container gardens, use an aquarium pump.

Floating plants, such as water hyacinths, floating heart, and floating water ferns also reduce algal growth. Water hyacinths grow well in a barrel garden. They reproduce freely and may need to be thinned out as summer progresses. The attractive lavender flowers have run rampant in some southern waterways, but they're not a problem here because they won't survive our winters. They can be anchored in place with a light piece of nylon string tied to a brick.

For each square yard of water surface, you may use two bunches of oxygenation plants, one medium to large water lily, and 12 water snails.

Fish and snails
After stocking the tub with plants, wait 4-5 weeks before adding fish. The plants must become established first.

Snails eat algae, fish wastes, and decaying vegetable matter. Fish help keep the water garden a healthy ecosystem. They trim excess foliage, and eat algae, mosquito larvae and other insects. Most aquarium fish are not hardy enough to survive a water garden.

A good rule of thumb is to use 1-2 inches (length) of fish for every square foot of water surface.

Gambezi (Gambusia affinis), also known as the mosquito fish, are effective at controlling mosquitos by feeding on the larvae. They are black fish that provide entertainment by flipping and jumping. They may even reproduce in water gardens. Over winter, keep them in an aquarium as they will not survive in a container garden.

Guppies will thrive in a small garden. Koi or goldfish are not recommended for a small water garden, as they can not tolerate the extremes in temperatures and gas.

If you don't plan to overwinter fish in an aquarium, bait shop minnows provide inexpensive insect control. Various shiner and fathead or crappie minnows work well. Sucker minnows are not recommended.

Acclimate fish to pond life by floating them in a plastic bag in the pond for 15-20 minutes. Fish will feed on algae and plants, but some people enjoy feeding them. This is fine as long as the food is limited so none is left to decay in the pond.

Overwintering the garden
Rather than overwinter plants, you may wish to treat them as annuals. Otherwise, you'll need to bring plants inside. Water lilies may be overwintered if cleaned and stored in moist sand in a cool, dark basement. Other tropical plants may be kept in crocks full of water in full sun and grown as houseplants. Free floating plants, such as water hyacinths, can be overwintered in a tub of water in a sunny place indoors.

Bait minnows may be overwintered in an aquarium, used for fishing bait, or discarded.


Reviewed 2000

  • © Regents of the University of Minnesota. All rights reserved.
  • The University of Minnesota is an equal opportunity educator and employer. Privacy