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How to Build a Small Water Garden

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A serene, reflective pool has its allure, it’s something that has always drawn mankind. There is something about water that relaxes us, that makes us feel peaceful and calm. It resonates with a deep inner part of us, a part perhaps long forgotten, but the connection is still there. After all, water is the very stuff of life itself.

Water features are becoming common additions to gardens these days, almost to the point of becoming clichéd! Unfortunately, they are more often than not just lifeless statues with flowing water. A pond has a far greater attraction than a plain old water feature, as it’s literally brimming with life. Anyone who has ever seen children around a pond, especially if it has fish in it, will know what a captivating effect it can have.

Most people in an urban setting have neither the space nor the expertise to construct a full-sized pond, but that doesn’t mean they can’t enjoy the benefits of a small water garden. Water gardens in containers are easy to build, and “half-barrel” water gardens are becoming quite popular for that very reason. Using a real wine barrel cut in half, or a similar sized plastic container, a water garden can be completed in an afternoon.

Beyond mere aesthetics, a water garden has its place in a permaculture garden. It can be used to grow edible aquatic plants and fish, provide a breeding site for rare and endangered fish or frogs, and produce many other valuable outputs.

A water garden is an aquaculture system – a diverse aquatic ecosystem, one of the most productive and efficient systems around. They are far more productive than any land based systems. This is because in an aquaculture system, aquatic plants have a constant supply of water that has nutrients dissolved in it, which they can easily take up. The waste from fish and other animals in the system provide additional nutrient to the plants, making for a very efficient and productive system.

Part I – Basic Water Garden Design Theory

In any water garden or pond, one of the most basic requirements to create a stable aquatic ecosystem are the various types of plants in it, each of which plays a specific role to support and sustain aquatic life.

There are four categories of water plants that can be included in a pond to achieve perfect balance.

  1. Rooted floating plants, such as water lilies
  2. Marginal plants
  3. Submerged (oxygenating) plants
  4. Floating plants


Image source: Virginia Cooperative Extension article, Urban Water-Quality Management: Purchasing Aquatic Plants. ID 426-044

Lets have a look at the four categories of aquatic plants in detail:

1. Rooted Floating Plants

Rooted Floating Plants, also referred to as Deep Water Plants, have their roots sitting in the bottom of the pond (or in a container on the bottom of the pond) and their leaves reach up to the water’s surface. They are sun-loving plants and can survive with 10-20cm or more of water above the plant’s crown. The best known examples include Waterlilies (Nymphaea spp.) and Lotus (Nelumbo spp.).

They produce floating leaves that shade the water, which reduces the growth of algae. They also provide shade and a hiding place for fish. Many rooted floating plants also produce spectacular flowers (most species need full sun 10 hours a day for best flowering).

Place these plants away from fountain sprays, as strong water movement or splashing water inhibits water lily growth. The leaves and flowers are constantly replaced and should be removed when they die off otherwise they will rot down and create more organic matter that can algae feed off.

Examples include the following:

• Dwarf or miniature water lily (Nymphaea spp.)
• Golden club (Orontium aquaticum)
• Hardy water lily (Nymphaea spp.)
• Lotus (Nelumbo spp.)
• Tropical water lily (Nymphaea spp.)
• Victoria lily (Victoria spp.)
• Yellow pond lily (Nuphar lutea)
• Water Poppy (Hydrocleys nymphoides)
• Nardoo (Marsilea mutica)
• Water Hawthorn (Aponogeton Distachyum)


Water Lily


Lotus


Water Poppy


Nardoo

2. Submerged (Oxygenating) Plants

Submerged Plants. also called Oxygenators, grow with their roots anchored in soil, but the leaves stay underwater. Oxygenators are essential for keeping the pond healthy and the water clear. The best known examples include Anacharis (a deep green plant with many delicate leaves, which will grow in water 15cm to 150cm deep) and Hornwort (dark green grass-like leaves, need 15cm to 30cm of water above the crown).

These plants absorb carbon dioxide and release oxygen into the water, and by oxygenating the water they help it support more aquatic life such as fish and beneficial aquatic insects. They also absorb excess nutrients in the water and help purify it, which reduces the growth of algae. Oxygenators also provide food and shelter for fish. The leaves, which are usually fern-like, lacy, or hairy, provide cover for the microscopic aquatic life forms which are an essential part of a balanced aquatic ecosystem.

Oxygenators can multiply very quickly and outgrow their space if not cut back regularly. Remove excess plants and compost them, they are a great source of plant nutrients. You will notice that fish eat these plants too, and that is not a concern because they can regrow quickly, and the fish just help control their growth.

These plants are usually planted in pots that are sunk to the bottom of ponds, so they sit vertically in the water, but they can also be left to free float on the water surface horizontally, though this doesn’t look as tidy.

Examples include the following:

• Canadian pondweed (Elodea or Anacharis)
• Hornwort (Ceratophyllum)

Some of these plants are Submerged/Emergent Oxygenator Plants, that is, they grow below the water’s surface, and also above it, examples include the following:

• Variable Water-milfoil (Myriophyllum variifolium)
• Water Milfoil (Myriophyllum propinquum)
• Water Primrose (Ludwigia peploides)


Anacharis


Hornwort


Variable Water-milfoil


Water Primrose

3. Floating Plants

Floating Plants are plants that float on the water’s surface, they do do not need soil, nor to be anchored to kind of base, and they grow by extracting nutrients from the water.

They control algae in two ways. Firstly, by shading the surface of the water, they restrict the light that algae needs to grow. Secondly, they are act as natural filters to remove excess nutrients from the water, which limits the nutrients available to algae.

They also have many other useful functions. Duckweed is a protein rich food source for fish, goldfish consume it greedily! Azolla is a tiny fern which supports nitrogen-fixing bacteria just like legumes do, so it captures its own nitrogen from the air. This makes it a great nitrogen source for the compost pile or as a source of rich food for worm farms.

Examples include the following:

• Duckweed (Lemna)
• Fairy moss (Azolla)
• Water hyacinth (Eichhornia crassipes)
• Water lettuce (Pistia stratiotes)


Duckweed


Azolla


Water hyacinth


Water Lettuce

4. Marginal Plants

Marginal Plants grow in the shallow margins around the edge of a pond, and they can survive with up to 10cm of water over the plant crown. These plants do best in still to slow moving water.

These plants can serve several functions. They can be decorative, adding colour and height to any shape of water garden, as well helping to blend in the edges of a pond into the surrounding ground. They also provide more practical functions, such as shelter from the wind, and shade. They also serve as a barrier around the water’s edge, providing protection to fish and frogs from predators. .

These plants are usually planted in pots, and set in shallow water on shelves or piles of bricks to achieve the correct elevation, or they can be planted directly in soil around a pond or stream.

Examples include the following:

• Arrowhead (Sagittaria spp.)
• Cattail (Typha spp.)
• Water iris (Iris laevigata)
• Water plantain (Alisma)
• Yellow flag (Iris pseudacorus)
• Lizard’s Tail (Saururus cernuus)
• Pickerel Rush (Pontederia cordata)
• Aquatic Mint (Mentha aquatica)
• Dwarf Papyrus (Cyperus papyrus)
• Horsetail Fern (Equisetum hyemale)
• Vietnamese Mint (Polygonum odoratum)
• Purple Loosestrife (Lythrum salicaria)


Yellow Flag Iris


Lizard’s Tail


Pickerel Rush


Aquatic Mint

Vietnamese Mint

Dwarf Papyrus

Putting It All Together

Now that we’ve covered the four types of water plants, we can look at how they come together to create a balanced ecosystem.

In Permaculture the principle of stacking describes the seven defined vertical layers of a forest garden that all work together to create a balanced ecosystem, as listed below:

  1. The canopy
  2. Low tree layer (dwarf fruit trees)
  3. Shrubs
  4. Herbaceous
  5. Rhizosphere (root crops)
  6. Soil surface (cover crops)
  7. Vertical layer (climbers, vines)

In aquatic ecosystems, we have four layers that similarly work together to create a balanced ecosystem.

  1. Marginal plants
  2. Floating plants
  3. Rooted floating plants
  4. Submerged (oxygenating) plants

This too is a “stacked”” arrangement in terms of utilisation of vertical space, and when these plants are brought together with the right proportions, all the plants in that system benefit.

The rules for constructing a water garden to get the “perfect balance” are simple, as listed below.

For one square metre of pond surface area you need:

For coverage of the water’s surface:

Now, with this theory in mind we can look into building a small half-barrel water garden.

Part II – Water Garden Construction

One of the easiest water gardens to construct is a half-barrel water garden. You can literally use any watertight container of sufficient size to construct a small water garden.

In this project, we’ll use a plastic half-wine barrel liner (pictured below) for our water garden. These liners are rigid containers that can be used without putting them inside a wooden half-wine barrel, and have a capacity of around 100 litres.

Whatever container you use, make sure it is clean. A word of warning though, if you intend to put fish in your water garden, do not use any soaps, detergents or chemicals to clean the container, the residue (which won’t be detectable by you) will be present in enough quantities to kill the fish!

The construction of the water garden consists of the following steps:

  1. Gathering of materials
  2. Potting up of water plants
  3. Setting up container with “shelves” to sit plants at their correct height
  4. Filling with water!

Step 1 – Preparation, Gathering of Materials

Gather all the materials required to build the water garden.

To build the water garden itself, you will need:


A plastic half-barrel liner and half dozen solid paver bricks

To pot up the water plants that will be placed in the water garden you will need:


Plants, plastic pots, garden soil, pea gravel and newspaper

A few helpful tips:

Step 2. Potting Up Water Plants, Step-by-Step Planting

Planting usually entails removing plants from where they are currently growing and placing them in their new location. When you do this, they take some time to re-establish themselves in their new homes. So, with any replanting, keep the following in mind when deciding to build a water garden.

Now, let us look at the planting procedures for each of the four types of water plants:

A. Marginal Plants

  • Marginal plants can be planted in regular plastic pots, just make sure you plant only one type (species) of plant per pot, otherwise stronger growing species of plants will take over when they start growing.
  • You can use several of the same plant in the same pot to create a denser planting, which will have more visual appeal.
  • Use black or dark coloured plastic pots so they won’t be visible under the water.
  • A good size plastic pot that can accommodate most marginals, and that is an ideal size for a half barrel water garden id a 6” (15cm) wide pot. For larger plants you could use a 8” (20cm) wide pot.
The steps to potting up a marginal plant are as follows:
  1. Select an appropriate sized regular black plastic garden pot and line it inside with newspaper so the soil doesn’t leak out.
  2. Add soil so that the container half full.
  3. Add some fertilizer (such as Osmocote, or a water lily fertilizer tablet) into the soil at the bottom of the pot, this way it doesn’t leach out into the water.
  4. Position the marginal plant in the pot with the crown at the top and then add soil around the roots, but leave the crown uncovered.
  5. Add a 1-2cm thick layer of pea gravel or river pebbles on top of the soil to hold it in place, but once again leaving the plant’s crown uncovered.
  6. Sit the pot in your water garden or pond, at the edge, to create a border or boundary around the water.
  7. Sit the pot in your water garden or pond, at the correct height, so that there is 5cm-10cm of water above the crown of the plant (elevate the container by sitting it on bricks or pavers to achieve the correct height if necessary).

B. Water Lilies

Water lilies grow from rhizomes. A rhizome is a horizontal underground stem of a plant from which new stems and roots grow. These rhizomes spread quite rapidly, so water lilies are planted in low and wide round or rectangular aquatic basket pots (pictured below).

  • Miniature water lilies are planted in medium sized (20cm) aquatic basket pots.
  • Regular sized water lilies are planted in large sized (30cm) aquatic basket pots.
  • You won’t have to worry about aquatic basket pots unless you are propagating your own water lilies – when you buy a water lily it comes in the correct sized pot, and all you do is sit it at the bottom of your water garden or pond.
  • Lilies can be introduced into your water garden or pond from spring until early autumn.
The steps to potting up a water lily are as follows:
  1. Select the correct sized aquatic basket pot and line it inside with newspaper so the soil doesn’t leak out.
  2. Add soil so that the container half full.
  3. Add some fertilizer (such as Osmocote, or water lily fertilizer tablets) into the soil at the bottom of the pot, this way it doesn’t leach out into the water.
  4. Position the lily in the pot with the crown at the top and then add soil around the roots, but leave the crown uncovered.
  5. Add a 1-2cm thick layer of pea gravel or river pebbles on top of the soil to hold it in place, but once again leaving the plant’s crown uncovered.
  6. Sit the pot in your water garden or pond, in the centre, or away from the edge, to give the leaves room to spread
  7. Sit the pot in your water garden or pond, at the correct height so that there is 15cm-45cm of water above the crown of the plant (elevate the container by sitting it on bricks or pavers to achieve the correct height if necessary).

NOTE: Other types of Rooted Floating Plants are planted the same way as water lilies, but you can use regular black or dark coloured plastic pots, 6-8” (15-20cm) wide instead of the fancy aquatic basket pots.

C. Submerged (Oxygenating) Plants

Submerged (Oxygenating) plants absorb their nutrients directly from the water, and as a result, require a lot less soil than other water plants, and can therefore be potted in much smaller pots.

These plants are often planted in a pot filled with gravel only, just to anchor the plants to the bottom of the water garden or pot.

The steps to potting up a submerged (oxygenating) plant are as follows:
  1. Take around five or six stems of the plant, and bunch them together
  2. Put the bottom end in a small plastic pot, and fill it with gravel or river pebbles.
  3. Sit the pot in your water garden or pond, so that there is 15cm-40cm of water above the leaves of the plant

D. Floating Plants

Floating plants just float on the water’s surface, and their roots hang into the water. These plants do not require pots or soil. Simply place these plants on the water’s surface and they care for themselves, that’s it!

How To Pot up a Marginal Water Plant

To familiarise ourselves a bit better with the actual process of potting up a water plant, we’ll step through how to pot up a marginal water plant in greater detail, in six easy steps.

1. Line the pot
Line the inside of a plastic pot about two thirds of the way up with newspaper.

This is to stop the soil from leaking out of the holes below.

2. Position plant in pot
Fill the container about one-third full of soil, then place the roots of the plant in the soil and continue to fill while holding the plant at the correct height in the pot.

Be sure not to plant it too deep. You can add several plants of the same type into a single pot if you want a fuller look.

3. Fill with soil
Add soil to the correct depth and firm down lightly, so it sits about 4cm below the rim of the pot.
Water the plant
Water the plant to settle the soil around the roots and allow excess water to drain off.

Note: If this plant will go into a water garden with fish, water with rainwater or dechlorinated water, as the chlorine in tap water irritates fishes gills.

Wash top dressing (pebbles)
To stop the soil washing out of the pot, you need to add a layer of river pebbles or pea gravel as top a dressing.

To remove any dirt or residue that might cloud or pollute the water, the top dressing needs to be washed.

One simple way to washing the top dressing stones is to put them into a pot with drain holes that are smaller than them so they can be rinsed under the tap.

Fill small rinsing pot or other suitable container with stones for washing.

Rinse top dressing under tap to wash out any dirt.
4. Apply top dressing
Cover the top layer of soil with about 2cm of river pebbles or pea gravel, stopping about 1cm below the top of the rim.

The potted plant is now ready to go into the water garden!

Step 3. Setting the Water Plants at the Correct Height in the Container

As mentioned earlier, the various types of water plants will tolerate a specific height of water above their crown. The “crown” of a plant is the point at which the stem and roots join.

As only one level of water exists in a container, we accommodate plants that need shallower water by building “shelves” in the water garden to lift them to the correct height.

Typically, marginal plants will have about 5cm of water above their crowns, and one way of elevating them is to use pavers or bricks. Ensure that the pavers or bricks are clean before putting them in your water garden.

Stack the pavers or bricks to the right height, and ensure that they are stable and support the base of the pot all way around as shown in the picture below.

Here is the marginal plant set to the chosen height, now it’s just a matter of adding the rest of the plants, and filling with water.

NOTE: If you are intending to put fish in your water garden, make sure you fill it with rainwater or dechlorinated water. The chlorine in tap water burns fishes gills!

The completed water garden, placed in the correct position, all plants placed in the container at the correct heights using pavers, and water added.

New water garden even passes inspection by the local fauna!

Additional Notes – Fish for Mosquito Control

Fish can be added to a newly built water garden to control mosquitoes, though you might give the water garden a week to settle and allow the aquatic ecosystem to stabilise before adding fish.

Various fish that work well in water gardens in Melbourne’s cold climate* are:

  1. Goldfish (Carassius auratus auratus)

  2. Rice Fish or Golden Medaka (Oryzia latipes)
  3. White Cloud Mountain Minnows (Tanichthys albonubes)

NOTE: The Rice Fish and White Clouds are both small fish and can coexist together, but don’t mix them with Goldfish, which will grow big and possible eat the smaller fish.

(*Melbourne, Australia, is considered a cold temperate climate, though we don’t usually get frost in the city)

Frogs and Tadpoles

If you wish to put tadpoles in your water garden, there is a bit more involved to turn it into a frog pond. I recommend reading up about frog ponds if this is what you intend to do, as this subject is beyond the scope of this article. Just a few brief points:

Other Useful Additions to a Water Garden

Part III – Water Garden Plant Care and Maintenance

Once you put together your water garden, it may look a bit sparse at first, as the plants may still need to grow in size to give it the look you want. Be assured that aquatic ecosystems are one of the most prolific and fast growing because of the constant supply of water and nutrient, in no time it will be possibly overgrowing.

Another point to keep in mind is that after a water garden is constructed, it takes some time to establish the right balance – it is a complex ecosystem and it has to settle in. If the water fills with algae, do not change the water, this is a normal part of the process. With enough shade from floating plants to cut out some of the light, and with the submerged pants growing and taking up excess nutrient in the water, the algae will reduce and disappear.

Each of the four types of plants will require their own particular maintenance around the year:

A. Water Lilies

Water lilies are heavy feeders, and should be fertilized every two months during the growing season (spring-autumn or September/October through to April/May) to ensure good flowering. Push a water lily fertilizer tablet into the soil near the roots, or put some slow release fertilizer granules (such as Osmocote) into a folded piece of newspaper or brown paper (this paper isn’t bleached and doesn’t contain harmful chemicals) and push it between the soil and the side of the pot.

Remove any dead or dying leaves (yellow or brown leaves) to reduce algae growth, if these are left in the water garden and rot down they will provide nutrients for algae growth. Removing old growth also helps promote new growth.

Hardy water lilies can survive in cold areas and do not need to be removed from the water as long as the water does not freeze down to the roots. If the water garden or pond is very deep, and the water lily pot is elevated, then it may be necessary to move the pot even lower to the bottom to ensure that the roots are below the level of the ice. If the water all freezes completely solid, then remove the water lily before this happens.

B. Marginal Plants

Fertilizer tablets can be pushed into the soil when the plants are flowering.

Since many marginal plants multiply by division, you will eventually need to unpot them and divide them up to thin them out a bit, then repot only some of them back into the same pot. This will probably need to be done every 1-3 years. The excess plants can then be repotted to make more plants, this is called propagation by division. Surplus plants can be given away or composted, or used to make more water gardens! With water gardening, you end up with lots of spare plants!

C. Submerged Plants

Thin out submerged plants if they become overgrown and crowded, especially if there are fish in the water garden and they have very little room left to swim around. The excess plants can be given away, or they can be composted.

D. Floating Plants

Floating plants reproduce quickly, and can cover the water’s surface.

Remember, only one third to one-half of the water’s surface should be covered with free floating and rooted floating plants. This means that any time, no more than half the surface of the water should be covered with floating plants. When they cover up more than half of the surface of the water, scoop them out by hand, with a net, or even a plastic garden pot, and give them away or compost them.

As mentioned before, duckweed makes excellent fish food, and azolla makes great food for earthworms in worm farms, so make best use of this free resource where you can.

In Conclusion…

As you can see, water gardens are quite easy to set up, and they can be set up in any container that can hold a reasonable amount of water. Once you have an established water garden, I promise you that you will have so much surplus plants that you won’t know what to do with them all !

So, if you’re lucky enough to know any other water gardeners, you’ll find that they are more than happy to give you spare plants they don’t want, and this way, you can construct your water garden for next to nothing!

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