Water gardening in containers. (2003 Feature Section--"Themes and Extremes").
Excessive you say?
Like most hobbies, container water gardening begins innocently enough, only gradually developing into a full-blown obsession. You start with a water hyacinth (Eichhornia crassipes) floating in a large decorative bowl on the patio table. A little fertilizer and a lot of sun and you soon have a stem of delicate, orchid-like flowers on your centrepiece. Soon you are looking for a larger container and visualising creative arrangements with larger plants.
Container water features offer everything a pond does--in miniature. They are low maintenance and eliminate the intensive labour of digging the hole for a pond. (Although large containers can be very attractive when partially submerged in the ground, which makes them easier to naturalize into a border.)
Containers are a great place to nurture new aquatic plants, or to keep the extra plants you just could not fit in the pond. They are also great for overwintering tender aquatic plants like tropical umbrella palm (Cyperus alternifolius) and dwarf papyrus (Cyperus haspan) that would not survive if left in the pond till spring.
You can always find space for a container: tucked into an empty corner on the patio or set into an empty spot in the perennial border. They are also perfect for an apartment balcony or condo deck.
The location you select is one factor determining the type of container you choose. Do you want a large, flat bowl with plants tumbling over the edge onto the patio table, or a huge ornamental ceramic pot coordinated with the colour of your outdoor furniture? Maybe you prefer half an oak barrel with a decorative iron pump beside the perennial border.
The location of your water garden will also determine the plants you can grow. Most aquatic plants prefer sun. If your container is in a partially shaded area, select plants that will adapt to lower light intensity, such as marsh marigold (Caltha palustris), lizard tail (Saururus cernuus), or arrowhead (Sagittaria latifolia).
Location is also important if your container includes a water circulation feature, whether it's an antique iron pump, a small spouting ornament, or a cascade through a series of containers. To circulate water you need to consider two things. The water feature must be near a ground fault source of electricity to supply the submersible pump, and it must be in a very protected location to prevent the wind from spraying the water beyond the container. In just one windy afternoon, you could lose most of the water from your container.
The ideal container
Any container that will hold water is a potential water garden. Explore garage sales for old crocks or wooden barrels. Even large terra cotta planters can be sealed to hold water. Older plastic plant pots may have drainage holes in the bottom, but they can be plugged with silicone, plumber's putty, or epoxy.
If you invest in a beautiful glazed decorator pot, consider placing it on a pedestal or stand. This will display the ornate beauty of the container and brings the plants closer to eye level.
If you're new to container water gardening, a large plastic pot is a simple, inexpensive way to start. Choose one in a dark colour so the container is not the focal point of the feature and debris or algae are less visible.
Select a container that is approximately the same diameter at the top as at the bottom. Containers that are narrow at either the top or the bottom can often accomodate only one plant.
Bigger is better in water gardening, and a half barrel makes an ideal rustic container, especially now that plastic liners have simplified the process of cutting, cleaning, and sealing the barrel.
Combine plants to achieve the effect you want. A single large plant in a tall urn makes a great focal point, or it can be the backdrop for a collection of lower pots. Plants like corkscrew rush (Juncus effusus `Spiralis') water plantain (Alisma plantago-aquatica), or pennywort (Hydrocotyle vulgaris) create interesting texture and contrast.
If you want the surface of the water covered with small floating plants, add duckweed (Lemna), or fairy moss (Azolla). Both multiply quickly and can totally cover the surface of the water. Water mint (Mentha aquatica) and creeping primrose (Ludwigia palustris) are also very enthusiastic--you may want to isolate them in their own containers and keep the pruning shears close at hand.
If you have a beautiful ceramic pot, keep the plantings simple to complement the container. Remember, your primary objective is to create an attractive display. Contrast upright plants like sweet flag (Acorus calamus) with arrowhead, and float a water lettuce (Pistia stratiotes) on the surface of the water.
Select plants that will disguise an old plastic container. Start with the vertical lines of miniature cattail (Typha minima) and flowering rush (Butomus umbellatus), which will produce umbels of pink flowers to complement the cattail foliage. Add the bright, variegated yellow, red and green leaves of Houttuynia cordata `Chameleon', and let the dark green leaves of golden water zinnia (Wedelia trilobata) or pennywort tumble over the sides to cover the container.
A half barrel is big enough to accomodate large plants like the white arum lily (Zantedeschia aethiopica) and yellow flag iris (Iris pseudacorus). It is also deep enough to successfully grow small water lilies like the yellow Nymphaea `Pygmaea Helvola' or `Chromatella', an adaptable cultivar that will tolerate some shade.
Plants are typically grown in pots and baskets placed inside the large water-holding container. Before planting, check whether all the pots you plan to use will fit inside the container so that you can alter the pot sizes if necessary. Black pots or baskets are less visible under water.
The top rim of the plant pots should sit about 5 cm. (2 in.) below the surface of the water. If necessary, place old plastic pots, cut to the required height, upside-down beneath them.
Alternatively, you could fill the bottom of the container with gravel or heavy loam, which gives you the option of creating a bog container.
Aquatic plants prefer low, wide pots, but due to space restrictions within the container, this is not always possible. I use round pots and drill several holes in the sides to allow the roots access to nutrients.
Plant in heavy loam and cover the soil with a layer of gravel. I disguise the light coloured gravel with a layer of black charcoal saved from aquarium filters, but this is not necessary.
Soak each plant in a pail of water before placing it in the water garden. This wets the soil and removes all loose debris.
If you are going to water garden indoors, the first thing is to protect the rug with a waterproof saucer under the container. The large, water-filled containers are heavy and difficult to move, so consider placing it on a plant trolley with casters.
I hesitate to suggest putting fish in a container water garden unless you have some experience in caring for them. Toxins in the container or the sealant can be harmful to fish, as can the chlorine and chloramine in our water. Special fish-safe fertilizers are required, and weekly partial water changes are necessary to remove minerals and salts that accumulate as water evaporates.
Water in a container may get quite warm, resulting in less oxygen available to the fish. Submerged oxygenating plants are a must if you have fish in your container. Consider putting fish only in large containers such as a half barrel, and provide surface coverage like water lily leaves.
Using a ratio of one inch of fish for each five gallons of water, you will be limited to two or three fish, as they will grow quickly if cared for properly.
Aquatic plants are heavy feeders and must be fertilized when grown in containers.
If you have fish in your container, place pond tablets in the soil when planting, and regularly throughout the summer, according to package directions. If you don't have fish, you can use 20-20-20. Fertilize each time you add water, but reduce the strength to about one-quarter of the recommended strength.
Other than fertilizing, maintenance is limited to deadheading. No weeding, no digging, definitely no watering--just sit back and enjoy.
This article originally appeared in The Gardener for the Prairies, Fall 2001.
Marilyn Brown is a Saskatoon gardener who shares her enthusiasm for gardening through the classes she teaches.
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|Date:||Jan 1, 2003|
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