Water in the Garden – Ponds and Pools Construction

Making a Garden Pool

simply magnificent!

a formal water garden.

Richly hued water lilies, reflections on a still, warm summer’s day, the plop of an eager goldfish as it surfaces to snap at a careless fly—such are some of the attractions of a garden pool. It is easy to make, can be completed in a day and will bring a lifetime’s interest. It can be of any shape, though one which fits in harmoniously with the surroundings is preferable.

Construction

Site it in full sun and well away from shrubs and overhanging trees whose leaves would blow into and foul the water. Unless you are using a preshaped fiberglass pool, which is simply sunk rim level into a suitably sized hole, you will need to dig out the shape you require. A rectangle, square or circle is best if the surroundings are formal, but an irregular, say kidney shape, is more in keeping with an informal area.

Whether small or large in size, it should be between 38cm/15in and 60cm/24in deep; otherwise it will heat up too much in summer and suffer from a lack of oxygen. In winter, there may be more ice in proportion to water, and again the fish would suffer. Slope the sides of the pool gently and cut out shelves in the soil, about 23cm/9in below the rim, to house marginal plants which are only covered with a few inches of water.

When the excavation is complete, line the bottom and sides with soft sand to cover any sharp stones which might otherwise puncture the liner, be it butyl rubber, plastic in the form of polythene or PVC, or PVC reinforced with nylon mesh. Lay the liner in the pool and ease out all the wrinkles you can. Then tension the sides by placing flat stones, paving or bricks around the edge. When you’re absolutely satisfied that not a stone can bore into the material and that there is a good foot of material overlapping the edge of the pool, fill in with water from a hosepipe.

Finally, trim the edges of the material to leave a generous overlap, and then cover this with 45cm/18in sq paving slabs set firmly in place with mortar. The slabs should project slightly over the edge of the pool to hide the liner and present a pleasing finish. A fountain adds great charm, oxygenates the water and the sound of tinkling water on a warm June day is extremely relaxing. Most kinds are easily fitted and an otter submersible pump will ensure a satisfying spray of water.

Planting The Pool

Allow the water to settle for a week or two before introducing plants. This ensures that any harmful minerals in the water are neutralized. If the water turns green, don’t worry. This is perfectly normal. Don’t attempt to empty and refill the pool—the water will only turn green again. The greenness is algae proliferating in the unshaded water. When aquatic plants shade the pool, the green algae will die out and the water will become crystal clear.

The Plants You Need

To create interest for much of the year, set the 23cm/9in shelf round the edge with marginal plants such as green, pink and cream-leaved Acorus calamus, golden flowered marsh marigolds and irises in many beautiful lavender and pinkish red shades. Plant them in small slatted plastic baskets.

Then you will need some oxygenating plants which help to keep the water pure and the fish, snails and other water animals healthy. Oxygenators are usually bought in bunches and are fixed to a lump of lead or a stone, with a rubber band and plopped into the pool where they will start growing regardless of soil.

These plants also stop the water from turning green and cloudy and provide the ideal spawning ground for fish. The different kinds include water thyme (elodea), water milfoil (Myriophyllum spicatum) and pondweed (Potamogeton crispum).

Floating plants such as water lilies and the water violet (Aponogeton distachyum) give a pool that luxuriant look in summer when their chalice like blooms in many colors shine excitingly in the water.

Planting Methods

Marginals and water lilies are best set in wickerwork or slatted plastic baskets. Pack their roots round with heavy, almost clayey soil. Never use manure, or this will discolor the water. Add a sachet of aquatic plant fertilizer, and top the soil with fine shingle to stop fish nosing it into the water and clouding it.

Set a newly planted water lily with its leaves just above the water surface. Lower it gradually as the leaves grow, until finally it is resting on the floor of the pool, with its extended leaves floating gracefully on the surface.

Calculating the Area of a Pool

To ascertain how much liner you will need for your pool, the length will be the length of the pool plus twice the maximum depth, and the width will be the width of the pool plus twice the maximum depth.

Materials

Years ago, before plastics were developed; concrete was used to construct a pool. Some people are still keen on using it, saying that it outlasts other materials. It can last for many years, but does have a tendency to develop hairline cracks. These are difficult to find. If the water level drops to a dangerous level, and you suspect such fractures, drain the pool, clean the concrete and paint the whole of the inside with Pondseal.

If you’re keen on making a concrete liner this is what you do: Dig out the shape you want, ram rubble or stones into the base, then, spread a 8cm/3in thickness of concrete over the excavated area. A good mix consists of 1 part cement, 1 part sharp sand and 5 parts sea shingle.

Allow the first layer almost to set, and then score it with the point of a trowel. A day or so later, spread this layer with a further 8cm/3in thickness of concrete. Fill in with water after 24 hours, then change the water four or five times before planting and introducing the fish.

Other Materials

Polythene

Probably the cheapest on the market. 500 gauge usually used. Ideally lay two sheets to increase durability, and make sure it is completely covered with water to reduce the effect of ultra violet light, which causes it to become brittle and crack.

PVC

More expensive than polythene; only a single sheet required. It has a greater resistance than polythene to ultra violet light deterioration.

PVC Reinforced With Nylon Mesh

This double laminated material is tough and durable and has a much longer life than both polythene and ordinary PVC.

Butyl Rubber

Specially toughened rubber sheeting with a very long life. It is unaffected by weather and ultra violet light and doesn’t wrinkle up so much as polythene or PVC.

Fiberglass

Sold as moulded containers, complete with shelves for marginal plants. Very durable, light to handle. Simply dig a hole and sink a fiberglass pool to its rim. Alternatively, dig a shallow hole, then pack the excavated soil up round the pool and build a rock garden round it. Then you have a rock garden with a water garden as a centerpiece.

A-Z of Pond Plants

water lilies in a garden pond

No pond is complete without water lilies.

Marginals

  • These are grown on the shelf around the inside edge of the pool and covered with just a few inches of water.
  • Acorus calamus variegatus (sweet flag)
  • Leaves striped brightly with green, pink and cream, 60cm/24in high. Yellow flowers, June to July.
  • Alisma plantago (water plantain)
  • Branching spikes of rose pink small flowers from June to August. 30-60cm/12-24in high. Leaves long and tapering.
  • Caltha palustris Plena (double marsh marigold)
  • Spreading hummocks of glossy rounded leaves set with short branching flower stalks topped with dense pom-poms of bright golden yellow flowers from April to June. Height 30-38cm/12-15in.
  • Cyperus longus (sweet galingale)
  • Attractive sedge with chestnut brown plumes of bloom from July to September. Height, 90cm/36in.
  • Iris kaempferi 'Higo Strain’ (clematis flowered iris)
  • Sumptuous reddish purple violet, blue or white extra large blooms from July to August. Height, 60-90cm/24-36in.
  • Mimulus luteus (monkey musk)
  • Yellow, maroon blotched pouch-like flowers from May to August. Rampant spreader; needs plenty of room. 20-45cm/8-18in high.
  • Myosotis palustris (water-forget-me-not)
  • Delicate sprays of intense blue flowers from June to August. Height, 23-30cm/9-12in.
  • Orontium aquaticum (golden club)
  • Impressive spikes of yellow club-like petalless flowers appear in from May to June. Height, 15—30cm/6—12in. Will either float or become a free-standing plant.
  • Pontederia cordata (pickeral weed)
  • Spikes of arresting purple-blue flowers from August to September. Attractive shining dark green oval leaves. Height, 50-75cm/20-30in.Sagittaria sagittifolia (arrowhead)
  • Grown for its imposing arrow head shaped leaves and stiffish spikes of white flowers. A double form is particularly impressive. Height 38-45cm/15-18in.

Oxygenators

These are submerged plants which keep the water charged with oxygen to ensure a healthy balance of floating and marginal plants, and fish.

  • Ceratophyllum demersum (hornwort)
  • Attractive whorls of rather brittle, green leaves, so handle with care when planting it.
  • Elodea crispa (curled Canadian pondweed) Stems clothed with downwards curving leaves.
  • Fontinalis antipyretica (willow moss)
  • Masses of soft feathery foliage.
  • Myriophyllum spicatum (water milfoil)
  • Lengthy stems set with candelabras of soft finely dissected leaves.
  • Potamogeton crispum (curled pondweed) Beautiful long thin, wavy edged leaves bright green to bronzy purple in colour.

Free Floating Aquatics

  • Azolla caroliniana (fairy floating moss)
  • Spreads to form a reddish green carpet of delicate fingered ferny growths. Ideal for shading the water to reduce the growth of water greening algae.
  • Hydrocharis morsus-ranae (frogbit)
  • Charming small white flowers appear surrounded by tiny rounded water lily-like leaves in June and July.
Stuart Jones
 

My name is Stuart Jones and I’m the guy responsible for most of the content on this website. I’m a horticulturist with over 25 years of experience in gardening and garden plants. To bring color throughout the year, I regularly grow a wide variety of plants, bulbs, flowers, shrubs and trees. Oh, and let’s not forget the fruits and vegetables to ensure the fridge is always stocked!

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