I love ponds. Some of my first memories are of peering into tannin-stained water, the ripe smell of warm mud and seeing a whole other world of water beetles, jellied frog eggs and water plants softly waving in a shaft of illuminating sunlight. Ponds have magical creatures which move effortlessly between water and land and are endlessly fascinating. For a time, my youthful mission in life was as self-appointed guardian of the clumsy helpless tadpoles, saving them all from the evil dragonfly larvae that preyed on them.
Although there are many ways to incorporate water into a garden, the most creative, gratifying and wild-life friendly is a natural pond. It can be the size of a small wading pool or hundreds of feet long and the best education on how it should look is provided by nature itself. By first observing how a natural pond is sited within the contours of the land, the natural rise and fall of water levels, growing habits of water and marginal plants and the interaction of the myriad of pond life, you will have the essential concepts of good pond design.
Most of us have limited space for a pond but that doesn't mean we can't have an ecologically healthy one without needing much, or any, mechanical help in the form of a pump and filtration. Of course, a stream or waterfall will need a pump, but filtration (keeping water clean) can be achieved using natural bio-filtration processes with help from microorganisms and plants. Like they say about gardening - feed the soil and the plants will take care of themselves. With ponds, nurturing the microbial life and plants will take care of the water health.
Placement.Your first design consideration is always placement. Full sun makes plant life happy but that includes algae. Green reflective water in the summer is to be expected and is healthy, however too much algae can suffocate pond life especially as it decomposes in overly warm water. If your pond is in full sun, get water plants and overhanging plants growing to provide shade and shelter. Waterlilies work well.
Natural context.Look for site contours and run-offs where a pond would occur naturally - it will feel settled and visually harmonious. If you don't have this then construct a version of a natural scene when you dig out the shape. Avoid under trees - too heavy leaf/needle drop may overwhelm the microbes ability to decompose it efficiently.
Fish or no fish?We love them and they bring life and colour to our ponds. Unfortunately they also eat life such as frogs eggs, tadpoles and water bugs, and they harass salamanders. If you can separate your pond into two distinct habitats, e.g, a higher level without fish and lower level with, separated by a stream (see photo), then you have the best of both worlds.
Also, in keeping with Darwin's law, herons love to fish for your fish. As much as you might love your $200 fancy koi, the heron loves them more. In my case the heron provides a management service as my 6 cheap goldfish exploded into 200 in a few short years. He harvests the large ones and leaves me with those yet unworthy of his efforts - which suits us both just fine. On a happy note, fish do eat mosquito larvae. If you decide against fish, however, there is a very effective ecologically safe product called "mosquito dunk". Fish should not need to be fed in a properly naturalized and balanced pond.
Habitat enhancement values.Virtually all Indigenous life is served by a pond. There are a myriad of hovering insects, water bugs, amphibians, birds, snakes (harmless here) and mammals that drink at the edges or find shelter in the pond. A natural pond/bog is one of the best things you can do for the environment. I have a charming pair of wood ducks who visit and grace the pond with their iridescent beauty. A heron drops in to fish and stands peering at me - gloomily - as herons do. Like finding a dinosaur in the garden. A variety of water bugs skim, dive, shimmer and skitter about (these tiny bugs are ferocious predators - they make short work of a nest of tent caterpillars. Dragonflies and damselflies will immediately commandeer a new pond and establish territory, a twig or the entire pond (apparently we have 87 species in B.C!) I see common dragonflies in my pond - that I believe are iridescent Blue-Eyed Darner, a small fiery red Cardinal Meadowhawk and a very large light green species. They are truly remiscent of tiny inquisitive dragons and one of the most fascinating and beautiful pond life to observe. It's never boring with a pond.
The best ponds for creature life have varying depths, stones, gravel, stumps, floating logs, twiggy branches, plants and muddy edges. At least one side should be gently sloped for easy access/exit and planted for shelter. It should have sunny warm spots for basking and shade under overhanging bushes and water lilies. Fortunately, this natural design is also aesthetically appealing to most people so it's a win-win.
Slime algae and invasive species. This stringy, obnoxious form of algae often appears in new ponds but gradually dies out with growth of microbes and marginal plants who compete for nutrients. It seems to come out of nowhere, even before any plants are introduced. It's a mystery. I often treat the water a couple of times with liquid products of concentrated bacteria/enzymes that work to break it down. Within a year or two it seems to dissipate on its own, assuming you are not flushing the pond and re-starting the "new water" cycle. A natural, balanced pond should only need to be topped up to replace evaporated water.
If your pond is interconnected to a natural stream, greater pond or ditch, you need to be very concerned about invasive fish and plants as these can spread to natural areas and effect significant harm. I love the look of the tall yellow flag irises (Irispseudacorus) but as these spread, I only use in self-contained ponds and I remove the seeds. Floating duck weed, often hitchhiking in water plants we buy, is terribly invasive and could change the ecosystem of an entire lake. Alien fish introduced to a lake inadvertently could empty the lake of other indigenous life. So be careful.
Aesthetics. Besides placement and visual integration with surroundings there are a few tricks to making ponds look natural. Liners need to be hidden but avoid using a ring of rocks around the entire edge as it rarely looks right. Build some rockeries and carry the rock over the edge into the pond instead. Or cover the edge with soil and plant compact rockery plants to create a dense carpet-like edge. Plants can draw water by osmosis so let them flow over into it, providing shelter to water life. Incorporate old stumps, logs and moss around the edge and in the pond (transplanted moss will thrive only if the new conditions are identical to where it was found. Moss found growing on stones may turn belly up if transplanted to wood. Moss also needs fiber (similar to bark or a bark layer) underneath to establish itself on a slippery, hot liner.
Practical side of pond building. My current pond is 100' long and undulating, with varying depths from 3 feet to only 4 inches. The sides are low and sloped with shallow "beaches" where birds love to bathe. I went with the idea of bio-filtration using a pump at one end to push water through a heavily planted gravel watery "bog" at the other end that functions as the bio-filter. A gentle current pushes water up from a perforated line of pipes through gravel and plant roots. The gravel bed is home to microbes that helps keep water clean and a gentle current prevents stagnation. There are many variations on this and other non-mechanical and mechanical solutions. This one works for my pond which does not have waterfalls or streams.
If you want to attract salamanders, frogs and other slow swimming creatures enclose your pump with the appropriate net bags to stop them being sucked into the pump. I learned this the hard way. :-(. Skimmers are not appropriate for a naturalized pond as fallen leaves and debris is important food for pond life. That said, too much decomposition in a small pond can be harmful. You need to be observant and check on your pond often.
I prefer soft liners as they are more amenable to the undulating contours of a naturalized pond. But, if you have large dogs, it can be damaged by all the climbing in and out. Concrete is an option but can be challenging to waterproof and cracked by large tree roots. Use round gravel (2 or 3 different sizes is best), not local crushed rock with sharp edges.
Every pond is unique and needs a carefully considered, customized solution. Start with what effect you want to achieve and what you want to attract to your pond and that will help in the planning and design process.
Ponds can be a gift of incredible beauty, an oasis for wildlife and a source of delight. Or, sometimes, they can be a maintenance headache and an expensive disappointment. Careful consideration, forethought and planning is a must if you are contemplating a pond.
As for me, they are so worth it!
A few good plants for a natural (standalone) pond:
· arum, arrowhead, bull rush, cattail, rush grasses (invasive), pond iris(s), water canna, pickerel rush, darmera, water lilies, marsh marigold, creeping jenny, maidenhair fern, native liquorish fern, water fern, ostrich fern, native mosses.
For more information about dragonflies: http://ibis.geog.ubc.ca/biodiversity/efauna/OdonataofBritishColumbia.html