At the centre of every harmonious garden lies a pond, thriving with a balanced ecosystem and teeming with life.
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There is something magnetic about water. As Tasmanians, we are anchored and brought to life by it. We seek the ebb and flow of the ocean, relish the salty air, and savour every moment our skin is wet. In the cooler months, we are drawn to the sound of rippling water, the reflection of the sky above in still ponds and lakes, and the gentle energy of millions of life forms beneath the surface.
This gift of harmony and equilibrium is not as simple as filling a hole with water, however. To create a pond teeming with life, we must first introduce life above by using a diverse range of aquatic plants. These plants foster pond health by inviting wildlife, oxygenating the water, and keeping it clear. The key to a balanced pond is to cover at least half its surface with plants and to include species at varying depths, allowing your pond to mimic nature and create a balanced ecosystem.
Understanding Water Plant Zones
OzWatergardens have developed a comprehensive guide on choosing and planting water plants. They’ve divided plants into five different zones, which indicate the depth each water plant requires. To find out the optimum water level for your plant, measure from the surface of the pot to the pond surface. As your plants establish, you can float them deeper into the pond as needed. Visit OzWatergardens’ website to view their Plant Zone Map.
Zone 1: Floating aquatic plants, such as Azolla
Zone 2: Bog plants and waterside plants, such as canna lilies, knobby club rush, and creeping jenny
Zone 3: Marginal plants, such as pennywort, elephant ears, and society garlic
Zone 4: 20-40cm plant depth, such as papyrus, marbled water fringe, and blue pickerel rush
Zone 5: >40cm plant depth, such as water lilies
Understanding Which Plants to Choose
Not all ponds are created equal. The depth of your pond determines how many plants it can support without overcrowding and disrupting the balance. Start by choosing plants that oxygenate and filter the water naturally, then add visual interest with flowering varieties. A simple rule of thumb is to follow a 3:2:1 ratio per square metre of pond surface, i.e. 3 oxygenating plants, 2 marginal plants, and 1 flowering plant.
Per square metre of pond:
3: Choose 3 plants that oxygenate the water, such as water milfoil
2: Choose 2 marginal plants, such as knobby club rush
1: Choose 1 flowering plant, such as water lilies
Water Plant Care
Your water plants will require seasonal maintenance to keep things tidy. A seasonal trim to reduce overcrowding and the removal of dead leaves will go a long way toward ensuring your pond retains its balance. You may also need to repot water plants into fresh aquatic soil — two parts loam, one part gravel, and one part sand.
If you’ve found the right recipe for equilibrium in your pond, you may not need to fertilise regularly. However, plants can benefit from an occasional boost of nutrients. We recommend adding slow-release fertiliser to the soil of your water plants rather than directly into the pond, as direct feeding can encourage the growth of algae and other invasive species.
Taking the plunge
There’s no such thing as instant gratification in the garden. It takes trial and error and many years of practise to find the right balance for your watering hole. Whether, like Costa, you’re turning an old pool into a natural pond, or like Martha Swales, you’re starting with a tiny pond, you won’t see evidence of frogs and dragonflies right away. But if you build it, they will come.
