Getting to grip with water garden basics. The balancing act using aquatic pond plants

Some people who have been attracted to the idea of having a water garden, virtually on an impulse, go out to buy themselves a pond liner, a few plants and a few fish. They’ve ‘bunged ‘em in’ with the honest intention of getting a few more plants and maybe a few other odds and ends at a later date.

So it happens that before they know it, the thing has taken off with enough vegetative power to send a rocket into space, and they no longer own a pool, merely a marshy place with the scraggy dead undergrowth of last year’s reeds marking spot where it was. If the pool had been planted out properly, it would be virtually self-sustaining, and as long as the fish population remained fairly constant, thoughts of filters (etc) could remain on the ‘back boiler’ for some time to come.

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A pond is not just a place to keep goldfish or koi ... plants thrive in and around ponds

I’ve always advocated water gardens to gardeners on the basis that here was yet another habitat, an opportunity for them to grow yet another range of plants. There was no need to be daunted by water-loving plants, in fact many of them would be quite familiar to many gardeners.

Plants like Houttynia cordata, Lobelia cardinalis and the little Sisyrinchiums could be given the opportunity to show how many strings they had to their bow!

Although the plants for water gardens are perennials that largely die back in winter, the maintenance would be less than any herbaceous border simply because there was no digging, pricking over, or mulching – just a 4 to 5 yearly root division and replanting.

This page answers a lot of questions about plants both in and around the pond.

But there is a difference in one very important respect:

In a flowerbed you are at liberty to plant what you want where you want, any number of plants. There would be a preferred spacing of plants; too many too closely planted might suffer from competition and disease; too few plants and you may have a problem with weeds, but there is no reason why they could not be all the same species or even the same variety.

With a pool or pond, you are effectively creating a little, self-sufficient, self-sustaining world, with all the ingredients interacting constantly; plants and animals, animals with animals and plants with plants, any one ingredient i.e. species of plant or animal cannot exist by itself, or it least if it does then it will quite simply take over the complete pool. Even the most timid and fragile looking water plant reveals itself to be an incredibly opportunistic beast of a plant without any competition.

Algal explosions in water gardens

Even if there was just water there, no plants, nothing, the basic forms of plant life, collectively classified as algae, would begin to arrive in 3 or 4 days, blown in on the wind as desiccated cells ready to burst into a population explosion initially feeding on basic minerals in the freshwater and then on the organic detritus that inevitably builds up in the pool from the very first day.

Soon the water would be more or less permanently thick and green, full of these microscopic plants. There are over 2,200 species of freshwater algae known to exist in the British Isles and there is nothing wrong with them as such.

In fact they make vitamin rich food for fish and other vegetarian animals, whilst providing a bit of oxygen to the environment as a by-product of photosynthesis, the reaction within green plants in which ultra violet light in sunlight is used to manufacture sugars for the plant’s energy and growth. The problem with algae is just that they reproduce themselves to such density you cannot see anything else in the water.

If you add higher forms of plant life, they will discourage the algae by using up the nutritional resources that the algae depend upon and quite often this entails leaf cover over the pool surface, blocking out the essential sunlight for the algae.

With a natural balance of different sorts of plants, fulfilling different roles but working together they create a harmonious balance that keeps the pool water sweet and clear. Sounds idyllic doesn’t it? Well I certainly would not want to live there, talk about ‘dog eat dog’, it’s really tough in there.

Take a look at the Perfect Pond Detective site to solve most pond and water garden problems

The essential ingredients, aquatic plants for ponds

There are a several sorts of ingredients or types of plant to choose from that will be used to plant out different levels or depths in the pool. There needs to be a representative selection of plants from each type to help with the balancing act in the pool, and as each type of plant takes up its role in the new environment they will provide a welcome home for any fish you subsequently add to your pool.

The most essential ingredient is the OXYGENATING PLANTS.

These are underwater plants that will provide oxygen during the day for the fish and other animals in the pool but also for the bacteria at the bottom of the pool. These are integral to the whole ecology of the pool and without them the pool would just fill up with dead plant material and fish muck very quickly. They need to be given oxygen 24 hours a day but in return can digest waste organic matter and dead algae converting them into simple compounds like nitrates that the plants in the pool, including the oxygenators, can take up for their own nutrition and growth.

The best and most efficient oxygenator is without doubt Laragasiphon major, otherwise known as Elodea crispa or Curly Pond weed.

Some folks claim that it is too rampant, but it only grows if there is the sustenance being created by the pool. It is easily kept under control, with a bit of judicious harvesting.

Most oxygenators are generally sold in bunches of five cuttings. Just push these into a small container of gravel to keep them in place then sink them to a level of roughly half a metre. Allow one bunch per 0.2 sq m (2 sqft) of pool surface. The cuttings will produce roots for anchorage as soon as they begin to grow and nutrients will be absorbed all over the surface of the plant. In hard water, a limey sediment precipitates itself onto the leaves. This should be gently brushed off to allow the leaves to function uninhibited.

Avoid certain plants, in particular Hydrocotyle vulgaris (Marsh Penny Wort), Myriophyllum proserpiacoides (Parrot’s Feather), Elodea Canadensis (Canadian Pond weed),

Next in importance are the DEEP WATER AQUATICS

These are mostly water lilies, Nymphaea. Available in virtually every colour of the rainbow except blue, the larger varieties act like great Hoovers of excess nutrients on the bottom of the pool. They also come in all sizes suitable for growing at specific depths from 6ins to 6ft (15cm to 180cm). Try to get a variety that is suitable to the size and depth of your pool and allow one lily for every 2.3 sq m (25 sqft) of pool surface.

They need to be planted into large aquatic baskets in a heavy clay loam, but only at half their final depth to begin with. Gradually introduce them to deeper water as their leaves get established on the surface. Beware that generally, the cheaper lilies are, the more vigorous they are. But even the most vigorous types will need a feed of slow release fertiliser or bonemeal pellets to get them going. They can be planted at any time from late spring onwards, as long as there is strong growth from a strong plant. Weaker specimens need to be nurtured on later in the season.

Keep them away from fountains and waterfalls as disturbed or flowing water upsets their growth.

Other deep water babies are the amazing Aponogeton distachyos or water hawthorn and the various forms of Nuphar lutea or brandy bottle plant. Owners of small ponds or clay lined ponds beware of the latter.

FLOATING PLANTS.

These float on the surface of the pool throughout the summer helping control algae by depriving them of light and using up their mineral resources. Native species like the Stratiotes aliodes or water soldier and the Hydrocotyle ranae (Frogbit) over-winter in various forms on the bottom of the pool. Species like the water hyacinth (Eichornia crassipes) and the water lettuce (Pistia stratiotes) are frost tender and need to be over-wintered under glass.

Be wary of any relatives of the duckweed including the floating fern Azolla coronilla. They make great duck food but very quickly and irretrievably cover the pool if there are no ducks to keep things under control.

Whatever you choose, there is no ceremony in planting them. Just put them in. If they sink to the bottom they will soon sort themselves out.

MARGINAL PLANTS

Marginal plants come in all shapes and sizes. They generally sit at the edge of the pool with the water lapping more or less at soil level. Some plants do revel in a depth up to 15cm as in the case of the Menyanthes trifoliata (bog bean) or Iris pseudacorus (the flag Iris) which makes some people like to classify some of the plants as ‘deep water marginals’, but these plants are generally tolerant of any depth and will grow out to the deeper depth anyway.

Marginal plants have the dual function of softening the edges of the pool area and using up the mineral resources in the pool. They provide secure cover for wildlife and act as a jetty for the activities of wildlife in and around the pool. Early spring colour, the beauty of them in reflection and their often striking foliage also help make them an essential ingredient for the water garden.

Allow at least one plant for every 0.5sq m (5 sqft). Plant them in aquatic baskets and place them in groups of the same variety in larger pools. In smaller pools, I am not sure that having more than one species in one basket works, certainly not in the long run. One of them always seems to win out over all the others.

Beware of what you choose, if there were ever any hooligans in the plant world, then a good number of them would be found amongst the plants often sold a ‘marginal plants’. For owners of smaller pools, be particularly cautious in choosing some of the larger and indigenous marginal plants like Typha (Reed Mace), Scirpus (Bulrush), Phragmites australis (Norfolk Reed). They are definitely questionable bedfellows. But you will find that even with these fast rooting, shooting pond fillers, their misbehaviour is moderated by a good cross section of other more ponderous representatives.

ANOTHER QUESTION OF BALANCE

Assuming that you have been well informed and that the pool has been planted with the right number of just the sort of plants that wont get out of hand in less than 12 weeks – what next? Time for the fish?

If you have waited 3 weeks and the water is nicely mature and things are beginning to move, then the time is ripe. You haven’t? Then you must wait at least three days, and treat the pool with a ‘Pool Conditioner’. Add them at only two or three at a time. Float them for 15minutes whilst the temperature of the water in the bag adjusts to the pool temperature. Roll down the top of the bag and this acts as a float and whilst it is there add a several small cups full of pool water to let the occupants get used to the new water chemistry.

The rule of thumb with fish is that with a pool at least half a metre deep you must allow two inches of fish per square foot of surface area. This adds up to a half a metre, nose to tail tip, per square metre. If you feed them, only feed them what they can consume in the minute or two that you are watching them. Too many fish with too much food and fish waste will mean you will soon be looking for a biological filter system.

So, with two inches of fish per square foot of surface area of the pool, you will be looking at two thirds of the pool covered with plant life. What? You only get to see the fish a third of the time? Hey, it’s better than not seeing them at all! Any less plant life and you are looking for a biological filter system again, which is a turbo version of the bottom of the pool – and that’s all lot more money spending and another story for another day.

You’ve got Koi carp? You’ve just spoilt the balancing act; the only recourse is technology. Get a biological filter system complete with U/V clarifier. The pond professor's latest water gardening site deals in detail with pond filters and UVC.

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