A recent innovation which is becoming increasingly popular is indoor water gardening. Both in the United States and Britain the use of indoor pools is spreading, not only in the lobbies of large business houses and apartment blocks, but also in private homes. A garden room or glass extension unit makes the project fairly simple, since these ensure good lighting which is most important for water plants.
In warm countries like Spain, Colombia and Brazil, indoor pools are often installed with fountains to convey a sense of coolness. In colder climates they are more likely to be still water, their main functions the growing of tropical aquatics which will not live outdoors and providing a home for exotic fish.
Any watertightmore than 20cm/ 8in deep is a potential water garden, so that large bowls, cisterns, aquaria, troughs and tubs are all suitable. The smallest of these will only hold one or two plants, so for a more comprehensive range a larger pool is necessary. Ideally this should be of concrete built down into the floor and connected to drains for easy emptying. It should also have raised sides, built with a wide ledge to provide a standing area for houseplants at the back and a seat in front. A slab of marble or other stone is ideal for the purpose. Raised sides also prevent dust and small objects from rolling into the water.
Heating can be provided by means of thermostatic immersion heaters, and extra illumination, if required, by underwater lighting or suspended neon lights. Concrete pools should be 30-40cm/12-15in deep.
Many garden centres sell prefabricated resin-bonded glassfibre pools. Although designed for gardens these are rigid enough to make free-standing pools when supported by timber frames. A simple shape is easier to set up than a complicated design.
There are four categories of aquatic plants used in water gardening: (a) those with submergedbut floating and ; (b) entirely submerged; (c) floating; and (d) with submerged but emergent leaves, and flowers.
The first group (a) includes water-lilies and lotus-plants requiring rich mixture and plenty of light. Hardy water-lilies, which have floating flowers of pink, red, white, yellow or apricot should be planted in aquatic(which have holes bored round the sides), in good sifted but fibrefree loam with a little bonemeal (about an eggcup full per pot). Plant them firmly, topdress the soil with clean pea-sized gravel (to prevent fish rooting in the soil and making the water muddy) and stand the pots in the pool. Spring is the best time for this operation.
Tropical water-lilies have stellate flowers standing above the water on long stems. They are variously coloured – white, blue, purple, pink and red, each bloom with an inner mass of golden stamens, tipped the same colour as the petals. Most are highly fragrant and there are also night bloomers with broader petals (the lotus types) which open their red or white flowers at dusk and close them soon after dawn. Tropical water-lilies have small bulb-like
tubers so can go into smaller 8-13cm/3-5in pots and should have some sand in the soil mixture.
Hindoo lotuses (Nelumbo nucifera) have spectacular flowers like huge red, pink or white roses standing well above the water, and large round parasol like leaves – all from a creeping banana-like rhizome. These can be grown in tubs or near the back of a concrete pool.
Group (b), the submerged plants, are vitally important since they keep the water clear and
also provide nurseries for fish ova and fry. They have practically no roots so must be weighted to get them to sink. Gather two or three stems together and gently press a narrow strip of lead round the bases, then drop them into the water. Submerged aquatics oxygenate the water and absorb the carbon-dioxide emitted by fish, so that the two together keep the pool balanced. Some are more efficient oxygenators than others, but for indoor pools any
of the milfoils (Myriophyllum; Tilleaa (Cras-sula) recurva; inacharis canadensis or Lagaro-siphon major – both of which resemble giant white-flowered elodeas – are suitable. They can be introduced at any season.
Floating aquatics, (c), shade the water, thus providing cool resting areas for fish in warm weather, and they starve out (and thus keep down) algae. Many are highly decorative.
The water poppy (Hydrocleys nymphoides) creeps across the water surface supported by small oval leaves and has three-petalled, golden, poppy-like flowers; fairy moss, Azolla caro-liniana is another creeper, with light green, red-tinted tiny leaves; salvinias are fern allies with small crinkled floating leaves, and the water lettuce (Pistia stratiotes) is well named on account of the shape of its silky green floating-rosettes. The frogbit, Hydrocharis mossus-ranae, has small, white, three-petalled flowers above the round leaves. Floating plants are simply placed on the water surface.
Section (d) contains many ornamental aquatics, rising to various heights. One of the most exotic is the Egyptian papyrus (Papyrus anti-quorum), a tall 1.8-2.5m/6-8ft reed with triangular stems and mop-like heads of grassy inflorescence. Elephant’s ears (Xanthosoma) have large yellow arum-like flowers and purple-veined, ear-shaped leaves on purple stems. Other plants worth growing are the golden-flowered jussiaeas (60-90cm/2-3ft) which look like elegant evening primroses; parrot’s feather (Myriophyllum proserpinacoides) with green, feathery, leafy stems which turn reddish at the tips and grow out of the water to trail over the pool edges; and the true water irises (laevigata) with blue, purple, white or rose pink flowers. Most of these can be planted in pots of plain loam and then stood in the pool with containers hidden beneath the water.
According to the water temperature all kinds of fish – hardy and exotic – can be kept in indoor pools. Fancy goldfish breeds like veiltails, moors, shubunkins and comets as well as golden orfe are reliable but becoming popular are the brilliantly coloured koi carp – with several colours, white, blue, black, red or mauve on the same fish. These are easily tamed and will thenfrom the fingers. Various tropical fishes are suitable for warm water.
Not only are fish attractive to watch but they keep down mosquito larvae and their excreta nourish the water plants.
Aquaria provide another method of cultivating water plants and keeping fish indoors. They can be free standing on metal supports or (if
there is room to tend them behind) let into walls or used as room dividers. Treated thus they make pleasant wall pictures, especially near a fireplace. They will also go under a TV set. Small strip lights above the tank, but hidden from view by a metal hood, give sufficient illumination to watch the fish and also keep the plants actively growing.
Aquaria mixture is usually washed coarse sand, spread over the base of the aquarium but slightly higher towards the back. Pieces of rock can be inserted to make a pleasant composition and plants pushed into the sand behind the rocks and towards the back and sides. Keep the front fairly clear in order to see the fish. Submerged plants like milfoils, Lagarosiphon major, and cryptocorynes are all suitable and show variation inshape, colour and texture. Plant these with the tank half full of water (you get a better idea of the effect) and fill it when the operation is complete.
A few small floaters like azolla and salvinias can then go on top and the fish put in soon afterwards.
A Tub Garden
An old sawn-down beer or wine cask is easily turned into a small water garden. Cut these down to about 50cm/20in from the ground and wash them thoroughly. Tubs which have held oily substances are difficult to clean unless they can be burnt over inside (stuff them with hay or straw, set fire to this and then turn upside-down before the wood catches fire).
Old casks which have stood about often leak, so keep them filled with water until the wood swells and they become watertight. They are then ready for planting.
Place 10-13cm/4-5in of heavy loam with a little bonemeal over the base and build up one or two side pockets with pieces of stone to take shallow water plants. Alternatively these can be grown in pots and stood on bricks. Plant a water-lily in the centre, with about six submerged aquatics and three or four marginals – like kingcups or marsh marigolds (Calthapalustris), water forget-me-nots (Myo-sotispalustris), both 23cm/9in high, and irises -around. Fill with water and add two or three small goldfish.