Once you have constructed the pool, you can begin to paint the water garden picture, that is to choose and establish the plants, and introduce the fish, bearing in mind the requirements of the pool as an independent ecosystem. For most gardeners, this is a time of great excitement, as the majority of plants that are grown in a water garden will be completely new, and the fish a wondrous mystery. The manner in which aquatic plants grow and their seasonal behaviour in a watery environment are fascinating.
The aquatic world is totally dependent upon plants to ensure its well-being; clarity of water will only result from the proper balance of plants, and the gardener has to assemble these in both scientific and artistic arrangements. Fish and other livestock add extra spice, for with few exceptions, all the creatures that inhabit the pool will be desirable or interesting. Many will arrive of their own accord, but by carefully selecting plants, you can entice others to set up home. The garden pool can become a haven for wildlife of all forms; whether they be lovely dragonflies, ugly toads or slinky newts, there is room for them all to live in harmony. The pool surrounds are also very important, for although they may not play an important part in developing a sustainable balance within the water garden, they do frame the picture and in many cases provide a unique opportunity to grow a range of plants which are tricky to establish elsewhere in the garden.
The boggy area beside the water also contributes to the life of the pool in that it is the home for many attractive creatures which utilise the water but are not sustained by it. In may cases of course the area beside a pool is dry and this too can have its advantages. The chance to grow plants of a character associated with dry conditions next to water is a garden designer’s delight, for artistic license can be invoked and the laws of nature theoretically flouted.
To ensure a trouble-free pool, it is essential to achieve the correct ecological balance. This not only guarantees water clarity, but also that all the inhabitants co-exist in harmony. Once the correct ingredients are in place, a balance will usually be maintained, provided that all aspects of the pool flourish; if one element fails, the ecological balance will collapse.
It is essential that all the elements involved achieve a reasonable harmony from the beginning. There are no hard-and-fast rules about what should be used when stocking a pool initially, for no two pools will be the same. There is likely to be great diversity in all aspects, from situation to water chemistry and nutrient levels. However, experienced water gardeners have developed rough-and-ready formulas which, although crude in scientific terms, tend to work well for most circumstances.
If we look at the principles of natural balance, we find that there are very distinct key areas that need attention. Submerged plants are the crucial element in achieving success, for they perform an invaluable and often diverse role. Their main task is to mop up nutrients in the water, and to provide oxygen during the daytime for fish and other aquatic creatures. However, they are also a food source themselves, a habit for aquatic fauna (which is another food source) and, in many cases, a nursery for young fish. Thus, their value in the pool’s ecosystem is incalculable.
Their most important role of removing excess nutrients reduces the incidence of algae, which is the bane of the pondkeeper’s life. Suspended single-celled algae turn the water green, obscuring the fish and many plants from view. If enough submerged plants are established, by virtue of being higher forms of plant life, they will starve out the algae in the pool by utilizing all the mineral salts upon which the algae would normally feed.
Submerged plants also oxygenate the water freely during the day, although at night the process is reversed and carbon dioxide produced. This will not be a serious problem unless there is an over-abundance of submerged growth, an overpopulation of fish and very warm night-time temperatures. In such circumstances, some of the plants may need removing. However, for most of the time, the more submerged plants there are, the better the pond balance will be.
Green water is also regulated by the amount of light available. Algae, like most other aquatic plants, enjoy full uninterrupted sunlight, so you can control it with shade. However, planting trees and shrubs to shade the pond is not a good idea, as this will prevent the desirable higher aquatics, like waterlilies, from growing well. The answer is to provide shade on the surface of the water itself, using floating plants and waterlily foliage, which will also add interest to the pool. These should not cover the entire pool, for complete shading will kill the submerged plants as well. No more than one third of the surface area should be covered if green suspended algae is to be controlled successfully and the submerged aquatics permitted to continue in healthy growth.
Fish are also essential elements when it comes to achieving a natural balance in the pond. They are invaluable for keeping pests under control, not only troublesome creatures like caddis fly larvae, which chew the leaves of aquatic plants, but also mosquito larvae which, if allowed to continue unchecked, will become adults and ultimately the scourge of the gardener. The waste matter they produce is of benefit to the plants, too. Other useful creatures are ramshorn snails, since they graze on filamentous algae, which is difficult to control in any other way.
Within this broad outline, there are places for many other creatures and plants, all of which have their parts to play in ensuring an ecological balance, which is easily upset if one aspect is ignored in favour of another.
When stocking a pool, the principles outlined previously must be considered carefully, and a formula for initial planting developed. Unless the plants have been chosen to produce a very definite visual effect, you may have to modify the formula slightly to achieve the desired balance. Categorize the plants by their mode of life, then choose sufficient to fill the requirements of the formula.
Calculate the surface area of the pool, excluding the marginal shelves in square metres or yards and, for every square metre or yard, plant nine or ten bunches of submerged plants. These can be grouped in clusters of containers, rather than being spread evenly around the base of the pool.
A similar calculation must be made before the quantity of waterlilies and floating aquatics can be decided upon. Remember that no more than a third of the pond’s surface area may be occupied by foliage at any one time. Any excess should be regularly removed to ensure that the submerged plants receive plenty of light.
If you want your fish to be happy, to grow and, ultimately, to breed, do not stock at a rate that exceeds 45cm/sq m (18in/sq yd). When calculating the length of a fish, include its tail. Ramshorn snails can be introduced freely, as the fish will control the population if it begins to get out of hand.
Once the formula for ensuring water clarity has been settled, specific varieties and species can be selected, within the limited constraints that the formula places upon you. As can be seen, the quantities of waterlilies, floating plants and submerged aquatics are all subject to restrictions, but marginal and bog garden plants can be introduced without constraint.
The marginal areas around the pool are very important, too. How you treat them will have a marked effect upon the overall visual quality of your water garden. In a very formal pool, their use is best restricted to three or four good basketfuls of quality architectural plants, like irises and rushes, which should be positioned with care. This will leave plenty of open water for creating reflections – a vital element in presenting a pleasing picture with a formal pool.
An informal pool can support massed marginal plantings, provided that you can reach the water’s edge at some point. For all water gardens, except the most unruly wildlife pool, container cultivation is essential. It is the only way to keep the pool under control. Never be tempted to plant directly into soil or the marginal shelf, for the plants will spread into each other and you will face a constant battle to keep the feature looking attractive. Tall plants in containers, such as the poker-headed typhas, must also be positioned carefully so that they will not be blown over.
Waterlilies are unquestionably the queens of the water garden. Indeed, for many gardeners, they are the main reason for establishing a pool. While they can form part of the cluttered picture of an informal cottage-garden-style pond, they will be seen at their best when planted in isolation in open water. Select varieties that are compatible with the depth of water and surface area available, ensuring that they are lifted and divided regularly according to their requirements. In that way, you will ensure that there will always be spreading flat lily pads and beautiful starry blossoms. If you choose the wrong variety for the prevailing conditions, or neglect to divide them frequently enough, the plants may climb partially out of the water in an untidy bunch and be sparsely flowered, or they may struggle to push vigorous leaves to the surface.
The least favoured of all plants are the submerged aquatics.
They are not very appealing to look at, but are essential nevertheless. Almost all flower, but the majority of blooms are insignificant. Only the water crowfoot (Ranunculus aquatilis) and the water violet (Hottonia palustris) produce blossoms of any quality. These should be used where flowers are required and where floating foliage will present no problem. They are not suitable for a reflecting pool, where submerged plants are essential to preserve clarity, but should appear as no more than dark masses on the bottom. Here, totally submerged species like the Canadian pond weed (Elodea canadensis), willow moss (Fontinalis antipyretica) and hair grass (Eleocharis acicularis) can be utilized.
To some extent, floating plants are an acquired taste. They can be both useful and invasive, but of all the aquatics, they are the most difficult to control, for even a modest breeze can transport them across a pool. Because of this, they are best used in an informal situation. In a formal water feature, the essential surface shade should be provided by waterlilies or other deep-water aquatics with floating foliage. The latter will root strongly into containers on the pool floor and will thus remain in position.
A bog garden is not an essential extension of a pool, but it does make a significant difference to the overall appearance of the feature. Bog garden plants can extend the flowering season at both ends, for they flower long before any other plants in the pool, and continue after the waterlilies have faded. However, their greatest virtue is their diversity of foliage, which not only offers amazing shapes and sizes, but colours and contrasts, too, especially as autumn approaches.
The danger faced by the enthusiastic gardener is over-populating the pool with plants, thereby excluding much of what is essentially water gardening’s most useful element: open water. While a certain number of plants will be necessary to ensure a balanced pool and clear water, the benefits of open water, and especially its reflective qualities, should not be underestimated. Moving water is also vital to many gardeners, for creating both fascinating visual effects and magical sounds. Its presence will have an impact upon planting ideas, as many aquatics do not enjoy growing in moving water. Consequently, how you will use the water is very important when considering which plants should be grown.
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