Water Gardening in Containers

Published on February 28, 2015

There is a style of water feature for almost every garden, no matter how small. All a person needs is some space outside that receives sun most of the day. But how do you build a water garden without a hole in the ground? Just find a container!

A Dwarf Papyrus standing among Water Lettuce.
A Dwarf Papyrus standing among Water Lettuce. 

Even large landscapes will benefit from the addition of container water gardens. A water garden in a container is one of the easiest types of water features to create—and can be very satisfying. We will want to keep this type of water feature simple, which we’ll discuss later. And they’re versatile; they can stand on their own or be placed on top of a table. For many, this less-permanent type of water garden can be the first introduction to the world of aquatic plants. The lushness and tropical look of aquatic plants has an appeal that most people really enjoy. The plants can attain this richness due to their access to an unlimited amount of water.

Choosing a container is the first and most important consideration. Anything that is glass, plastic, ceramic or sealed wood could work. Of course, if the container has holes, the holes will need to be sealed. A container that does not have holes is even better.
There are containers made just for use as water gardens. Most of these are thick plastic or pottery that is heavily glazed on both the inside and outside. I have heard that these heavily glazed pots are called “jars.” They can be pricey, but are very decorative. Containers glazed just on the outside are commonly available and they will work fine if properly sealed.

In fact, most people do choose to use a container designed for other purposes. Good examples of interesting containers are urns, crocks, half whiskey barrels (a plastic liner placed inside will seal it, if necessary), and even glass pie dishes. Try to avoid anything made of metal. Of course, steel containers can rust. New galvanized containers and any copper container can be toxic to life, although old galvanizing that has been dulled with weathering should be fairly safe. Containers as small as a quart of water work well, but may only hold one kind of floating aquatic plant. These small containers do require more attention due to the need to add water more frequently.

Picking Plants

Displaying beautiful aquatic plants is the reason the container is set up, so what types of plants work best? Almost any kind of floating plants are excellent for containers— especially the small “floaties,” like my good friend, Deb Spencer, calls them. They do not require being planted in a pot and they obtain 100 percent of their nutrients from the water. They are easy to plant, too—just toss them into the container! Good examples of floaties are Water Hyacinths, Salvinia, Azolla and Floating Heart.

Even really small containers work easily for aquatic plants. This frog container holds approximately 1.5 cups of water. Since it is so small, water needs to be added every day. Water Lettuce and Salvinia work well in this situation. (Click to expand)
Even really small containers work easily for aquatic plants. This frog container holds approximately 1.5 cups of water. Since it is so small, water needs to be added every day. Water Lettuce and Salvinia work well in this situation.

Since most of these containers do not have much fish excrement and/or decaying organic matter for plant uptake, we need to add nutrients. Liquid aquatic plant fertilizer can be added to the container to keep these plants looking good.

Potted plants also work well. Two varieties of water lilies, Helvola and Indiana, are very small, hardy varieties that I like because they stay small and are very floriferous. Lotuses of various sizes can be used. A variety of lotus called “small bowl” is suitable for the smaller containers, and the larger varieties of lotus can be devoted to a container all by themselves. Water lilies and most lotuses can safely be placed directly on the bottom of the container. Their leaves will be able to reach the surface.

Marginal plants like Cannas, miniature cattail and Taros are also excellent candidates for containers because they add the vertical element and give a very lush, tropical look. The most difficult aspect of using marginal plants in containers is getting the plant at the proper water level. Most marginals look and do the best with only an inch or two of water over their crown (over the top of their pot). Of course, the plant pot needs to be completely immersed in the container; otherwise, with the pot showing, you will have a faux pas. Very tacky. To get the plant at the right depth, I recommend using a “stand” under the plant pot. I like to use fired bricks (not concrete since it will alter the chemistry of the water) or small, black plastic storage crates that can be cut to the right height if needed. Wind can create problems with upright plants, so I also recommend using wide plant pots for tall plants.

Variety is Key

The most important aspect of using aquatic plants in containers is to include two or three different forms so that the container has balance and interest. This is just plain good garden design. Be sure to include an aquatic plant that has leaves that float directly on the surface, like a water lily. Then add an upright marginal plant, like a miniature cattail. Finally, you can add a floating plant, like Water Lettuce. Containers with only one plant can also look great, depending on the container and the plants. Miniature cattail in an old-fashioned crock looks very nice, as both the crock and the cattail have upright forms. A lotus in a container that is buried in the landscape can look magical…like a miniature pond.

Ultra Balance
 All but the floating plants should be planted in individual pots placed within the container. Use the style of pots without holes; they will not leak soil into the water. These pots are commonly available from water gardening retailers. Remember, a wide pot should be used fo rtall, marginal plants to keep the plants stable in windy conditions. Narrow, deep plant pots are not a good choice for aquatic plants. Most terrestrial plant pots are the narrow and deep style. They can work, but are not the best choice. Pots with holes can be used, but do cover the holes with landscape fabric to retain the soil. Use regular topsoil, to which aquatic plant fertilizer tablets have been added, as a planting medium. Do not use potting soil, which can have additives that float or can cause anaerobic conditions underwater. After the plant is planted in its pot, cover the rest of the top of the pot with a one-inch layer of pea gravel to keep the soil in the pot.

Livening Things Up

In containers that have a volume of 15 gallons or more, it’s fun to add a couple of goldfish that you can purchase for only a dollar or two. As long as you only add one or two small fish (one inch or so) in this size container, you do not need to aerate the water. The plants are critical in keeping the water fresh and aerated enough for this kind of fish population. These fish will eat all mosquito larvae, as well as other insects that may show up. In smaller containers, or if you choose to not add fish, then you will want to add Mosquito Bits or Mosquito Dunks to the water. These floating wafers contain bacteria that will kill many kinds of aquatic larvae, including mosquito larvae. The water is still safe for pets, people and any other life.

These companion jars (containers) have Helvola hardy water lily in them. The small jar holds about 1 gallon of water and the larger one holds about 2.5 gallons..
These companion jars (containers) have Helvola hardy water lily in them. The small jar holds about 1 gallon of water and the larger one holds about 2.5 gallons.

Normally, I would not add a water pump. The pump is not necessary to keep the water fresh as long as we have the plants, which are critical in keeping the water fresh. Of course, the reason we are setting up the container in the first place is to display aquatic plants. You can add a pump, but most water plants do not do well when water is constantly splashing over the upper surface of their leaves. So if a water pump is added, then a much larger container should be used so that plants can be kept away from the splashing water. Adding a pump to create the sound of water is appealing, but when plants are present it is more appropriate for larger features.

Easy Care

The ease of maintenance is the best part of a water feature without a water pump. Keep it filled and make sure to add chlorine remover if adding more than an inch or two of treated water at a time. If you are just topping it off, then the chlorine remover is not necessary. The chlorine dissipates quickly and is diluted in the rest of the volume of the container. You will need to add chlorine remover when first filling the container or when adding a lot of water at once.

Adding Mosquito Dunks into small water feature containers is an easy way to kill all mosquito larvae.
Adding Mosquito Dunks into small water feature containers is an easy way to kill all mosquito larvae. If fish are in the containers, then adding these doughnut-like dunks is not necessary. (Click to expand)

Place the container in a spot that is “up close and personal,” as I like to say, for easy viewing. On a deck, next to a sitting bench, on either side of a door or along a path are ideal places. The container needs to have direct sun for at least 50 percent of the available daylight for the plants to do well. You will get full potential of blooms from the lilies, along with the lush, tropical foliage. If given less sun, the blooming plants will not have as many blooms. Yes, you may get a couple of blooms, but the plants will be more “leggy” as well. It is also absolutely necessary for the container to be level. If it is not level, it will not look good. The uneven water level in the container will highlight the unevenness of the container.

Debris that may fall into the water will need to be kept to a minimum. Tree leaves or decaying water plant leaves need to be removed. A lot of decaying organic matter or uneaten fish food can cause the water to have a green, single-celled, free-floating algae bloom. So, feed the fish only a very small amount. They will also supplement their diet with natural foods. When feeding, all the food should be gone in less than a minute. Some fish owners will not feed their fish anything, but if you do feed them they will be friendlier. You are the giver of food and they will love you and want to be close to you when you peer into the water. If you don’t feed them then you will hardly ever see them because then you are a “predator” to them.

Trim the plants back if they overgrow the container—give excess plants to friends or add them to the compost pile.

Avoid the Deep Freeze

Overwintering your plants, fish and containers is the last step to consider. If you want to save any tropical plants, they will need to be removed before any threat of frost and placed in a greenhouse or in a lighted environment. Most of the time, it is more practical to throw these away. I know, it’s tough throwing healthy plants away! All floating plants can be composted, and they are inexpensive to purchase again in the spring. The right time to actually dismantle the container is after the water really starts to cool down and before the container freezes. Hardy marginal plants can be moved into a garden spot and buried in the soil to the pot’s rim. They can freeze solid in the ground and still survive.

This relatively small container is plastic but has the “terra cotta” look. Red-stemmed Thalia is a fast grower, especially when nutrients are added to the container every week. Here, shepherd’s hooks are holding onto the container to keep it from tipping over in the wind.
This relatively small container is plastic but has the “terra cotta” look. Red-stemmed Thalia is a fast grower.

Hardy water lilies and lotus are easy to overwinter. They can either be placed at the bottom of a 30-inch or deeper water garden, or they can be brought inside. If moved inside, cut off their surface leaves (do not cut the new leaves at the crown) and place the plants in a black plastic bag while still dripping wet. All they need is to be wet and cool. Tie the bag at the top and place in the coolest spot in the basement. The cooler you can keep them (as long as they’re above freezing), the better. If a cool spot is not available then ask a friend for a spot in his basement. If kept warm, they will want to grow. Check the bag in the middle of winter to make sure that the plants are still wet. In early spring, move water lilies and lotus back out into the outside container. They may start growing early, depending on the temperature at which the bagged plants were kept.

Your fish can be brought in for the winter and placed in an aquarium or tub or can be taken back to the fish store, although some people have a tough time giving away their pets.

Keeping Things Fresh

Your containers can have an entirely different look from one year to the next, depending on the plants used. Changing the location where the container is placed will also change the look and provide new interest.

Containers are a popular addition to any garden, and when you use them as miniature water gardens they are especially attractive. They are simple and have a very lush, tropical look to them. Plus, the variety of containers and aquatic plants to choose from makes the container water garden an even more attractive feature that will enhance any outdoor space!

Aqua UV

2 thoughts on “Water Gardening in Containers”

  1. Excellent article. I’ve read many, this is the first that warns of using a metal container…i had to learn about that the hard way. Clear advice about over wintering as well. Great job. Sx

  2. Thanks Sara

    Yeah — I learned the hard way 50 years ago when I put tropical fish in a new galvanized tub. Hopefully, all of our readers will benefit from lessons learned.


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