Pondering ponds

There are many benefits to integrating ponds as part of your client’s landscape, yet many landscapers shy away from them due to perceived complexity. Pond expert Peter Brymer shares his insights on well-installed ponds and why they work

When I advocate for landscapers and homeowners to consider building ponds, I’m talking about well-designed and constructed ones that mimic the natural ecosystem – not the old-style, ‘hole in the ground with dirty water’ concept that many homeowners inherit.

Unfortunately, because there are so many of the latter around New Zealand, landscapers tend to shy away from recommending them – but a pond that emulates nature can be low maintenance and attract a lot of birds, insects and other wildlife.

Nature has been looking after bodies of water really well for millions of years, all you need to do is give it the ability to do so. This is what you need to provide:

Oxygen – water needs oxygen to avoid stagnating, and this can be provided by adding a waterfall. As in nature, waterfalls need to be going 24/7 to ensure a steady generation of oxygen.

Healthy bacteria and microbes – a pond needs plenty of solid surface area for these to develop, such as river pebbles along the bottom.

A biological filter – use this to house a large colony of aerobic beneficial bacteria and microbes, which the whole water volume is pumped through continuously. The water leaving this filter will be depleted of oxygen, so it needs to pass over the waterfall to be replenished.

A pump – this is needed to circulate the water, so the oxygen is spread all around the pond. In an average pond, the water will go down the waterfall at one side and be sucked in the other side to get a good turnover rate.

Aquatic plants – these remove the nitrate that is naturally produced by decaying organic matter. If there are no plants to do this, nature will use the only other plant available – algae – which most homeowners try to avoid in their ponds.

These are the basic components required to have a low maintenance and thriving pond. However, remember that mimicking nature is key, so don’t do things that throw nature out of balance, such as having too many fish.

Does size matter?

A pond can be any size, as long as it incorporates the components above. The size of the biological filtration should be chosen based on the size of the pond, and the turnover rate increased for smaller ponds, as these are more unstable than larger ones.

The average pond holds 2,000 to 3,000 litres of water. The most popular urban pond would normally be 4.5m x 3m and require an area twice that size to accommodate it. Waterfalls should be kept low and blended into the landscape.

Plant selection simplified

There are specific wholesale aquatic plant sellers, such as Glenbogal Aquatic, who provide an impressive range of options and literature about each option. There are different recommendations depending on the depth, and Glenbogal recommends stepped shelves to accommodate all four zones.

Zone 1 - moisture-loving plants

There is a large range of moisture-loving plants for the edges of ponds. Depending on the moisture of the planting area, options do not need to be specific aquatic plants – but no watering will be required. Options include Myosotis scorpioides (water forget me-not), which has pretty blue flowers that sit atop velvety leave, but any moisture-loving plant would thrive, even vegetables.

Plant options include Impatiens, which you may think of as a terrestrial plant, but these dainty f lowers do quite well planted as an aquatic marginal. These cheery shade-lovers can be planted in between rocks or at the edges of a stream. They’ll mound as they grow and create a striking focal point in any pond.

Zone 2 - marginal plants

Marginal plants are those which grow around the margins of the pond where the water is shallow. They usually have their soil and crown underwater, and sometimes their lower foliage as well. They are generally placed on planting shelves within the pond to a depth of up to 15cm.

Zone 3 - deep marginal plants

Deep water aquatic plants are those which grow on the bottom of the pond or on the deeper shelves, so that they have 15 to 40cm of water over their crown. Options include Rotala rotundifolia (Pink Sprite) and Saururus cernuus (Mouses ear).

Zone 4 - submerged plants

These varieties are the most commonly asked about. They will grow permanently under water with the majority of the foliage submerged. Many plants, however, will have leaves and in some cases flowers that will float on the surface.

A common name used for these plants is ’oxygenators’. This name is somewhat confusing, because while they do oxygenate the water by day, they produce carbon dioxide at night.

The most popular of the submerged plants is Anacharis, which needs to be rooted in the pond substrate or potted in sand. It has tiny white flowers that develop on the surface of the water in the summer. Each stem has short, thin leaves whorled around it, like a bottle brush.

Other options include Sagittaria subulate (Dwarf Sagittaria), Rotala indica (Bean Stalk) and Ranunculus lingua (Water Buttercup).

Using an aquatic plant seller is recommended, thanks to the expertise and information available. Most importantly, proper aquatic plant suppliers use low-nutrient aquatic soils, which is essential.

DO NOT put regular potting mix in your pond! If you have purchased plants from another plant supplier, hose them down so each plant is bare rooted, then plant them in the sand of pebbles in the pond. This means the roots have nowhere else to get food but the water – which is what we want.

When it comes to maintenance, a pond is a water garden and needs to be treated as such – if a plant is getting too big, reduce it.

Regulations

According to the Fencing of Swimming Pools Act, barriers are required for ‘residential pools’ and 'small, heated pools' that:

• Can be filled with water to a depth of 400mm or more, and

• Contain water (regardless of the amount of water).

However, a residential pool barrier is not required for garden ponds and similar water hazards, which are not intended to fall within the definition of ‘pool’ in the Building Act.

We recommend edging the pond side with plants and rocks or hardwood logs to deter anyone from getting too close. Also, stepped planting shelves around the pond makes it safer because children and pets won’t fall straight into deep water and can climb out easily.

Benefits of ponds

Garden ponds enhance aesthetics and attract wildlife, boosting biodiversity and enhancing local ecosystems. Studies show they attract 20% more birds than a bird bath, as well as

insects.

A healthy pond has a number of insects living in it – including boatmen, water beetles and dragonflies – but no mosquitoes, as they don’t like aquatic plants, moving water, or dragonflies, which will eat up to 800 mosquitoes a day!

Last but least, ponds provide natural cooling, create a serene ambiance and can also increase property value.

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NZ Pond Supplies director Peter Brymer is New Zealand’s supplier of quality pond equipment from Aquascape and Aquatic Lifestyles. A big believer in the Aquascape EcoSystem Pond, he started researching the US-based company in 2009 and spent two years tailoring it to New Zealand, before he introduced the product to New Zealand in 2012.

Peter offers a consultancy service for landscapers working with existing ponds or looking to incorporate a pond. He can provide advice based on photos or site visits as required. Email him on nzponds@gmail.com for enquiries.