Planting water plants

No garden pond is really complete without water plants – whether floating on the surface, submerged or growing at the waters edge.

The easiest way to maintain a sparklingly clear, fresh-smelling pond without installing a pump is to grow a good range of aquatic plants and to include fish and snails. Ensure, too, that the pool is in full sun so that plants thrive and flower reliably.

Water plants with large, floating leaves – waterlilies for example – also provide shade and shelter for aquatic wildlife, and help keep down algae, which needs bright sunlight to thrive.

You can choose your own water plants, keeping in mind their final height and spread, and their leaf and flower colour and form. Or buy one of the special collections offered by water garden centres. Either way, it’s important to plant them correctly, since each type has different requirements.

Established water plants sold in plastic containers can be planted all year round. But with young plants just starting into active growth, it’s safest to begin planting in mid to late spring, once the weather is consistently warm.

Planting baskets

It is necessary to use a container when planting in ponds with rigid or flexible liners, as opposed to natural ponds with soil on the bottom. This also helps curb excessive growth – often a problem with aquatic plants.

Purpose-made, perforated plas-tic baskets, available from water garden nurseries and aquatic sections of larger garden centres, are ideal. The holes allow water to circulate through the soil or potting compost. Sizes range from 5-28cm (2-11 in) in diameter; most are square or cylindrical, and dark coloured, so they can’t be seen once submerged. Fine-mesh containers don’t need lining; wide-mesh containers should be lined with clean, coarse hessian sacking, long-life polythene or nylon liner.

You can buy aquatic potting compost containing special slow-release fertilizer or use a good heavy loam, free of roots and other organic debris which rot and release toxic substances into the water. Never use soil recently enriched with artificial fertilizer, which will also pollute the water.

Mix a couple of handfuls of sterilized bonemeal with each bucket of loam. Alternatively, use superphosphate at half this rate, or insert proprietary sachets of special slow-release phosphate fertilizer when planting. Add a little water until the mix remains in a lump when squashed in your fist, rather than falling apart. This helps prevent soil being washed out as the container is put in the water.

Direct planting

You can cover the bottom of a rigid or flexible plastic pond with a 15cm (6in) layer of special aquatic soil mix or loam, protected with a 1.2cm (’/lin) layer of pea shingle, to add weight and prevent the plant being disturbed by fish. Plant deep-water plants and some oxygenators directly in the bottom. This method is only suitable for a pond that is new or can be completely drained, and you must wait for a month before adding fish. Another drawback is that it is difficult to control the growth of vigorous deep-water plants, such as some waterlily varieties.

Planting deep-water plants

As the name suggests, deep-water plants need a good depth of water above their root-ball, from 15-45cm (6-18in), although some will survive in shallower water provid- ed they have plenty of soil depth. They usually have floating leaves, with flowers on or above the surface, which provide shade and shelter for fish and other animals.

Although there are only a few varieties available, many are quick to establish themselves and yet are non-invasive, so offering a useful alternative to waterlilies. There are also varieties that can tolerate partial shade and flowing water.

Popular varieties include Cape pondweed, also known as water hawthorn (Aponogeton distacb-yos), which has white petals and black anthers; and water fringe, or floating heart (Nymphoides pelta-ta) with buttercuplike flowers.

They should be planted in bas-kets containing a rich neutral or slightly acid soil, covered with a 1.2cm (’Ain) layer of pea shingle. Place the baskets on the bottom of the pond or on a shelf at a distance of one plant per square metre/yard.

Planting waterlilies

Waterlilies (Nymphaea species and hybrids) are the most popular deep-water flowering plants.

There are numerous varieties to choose from, ranging in flower colour and vigour, including miniature ones for shallow ponds: Vigorous types plant 23-90cm (9-36’m) deep.

Medium types plant 15-45cm (6-18in)deep.

Small types plant 15-30cm (6-12in) deep.

Miniature types plant 10-23cm (4-9in) deep. Some nurseries trim waterlily roots ready for planting. If this hasn’t been done or if the plant has been damaged in transit, use a sharp knife to remove the older, brown anchorage roots. Cut back the newest, white anchorage roots to about 10cm (4in). Cut off dead and broken leaves.

Line the basket, if necessary, and fill it to within about 2.5cm (lin) of the top with the soil mix. Plant tuberous varieties with loglike, bulky anchorage roots and with fibrous, rufflike roots just below the crown, vertically or at a slight angle. Plant rhizomatous types, with long, fleshy anchorage roots, horizontally, about 2.5cm (lin) below the surface.

The growing points of both types should just protrude above the surface of the soil or potting compost. Firm the soil well, ensuring there are no air pockets. Cover the soil with a 1.2cm (0.5 in) layer of pea shingle.

THE NUMBER OF WATER PLANTS YOU WILL NEED

Choose varieties that are best suited to the depth of water in your pond. If a waterlily’s stems are too short for its leaves to reach the surface, it does not harm the plant to be totally submerged. The old leaves can be cut off and the plant’s stems will grow up to the surface and produce new ones.

If you want to retain the leaves and any flowers, raise the basket on bricks . Or, with a new pool, you can raise the water level gradually, allowing the level to follow the growth of the shoots.

Planting marginals

Marginal plants are grown on the shallow planting shelf of rigid or flexible plastic ponds, or in the shallow water or constantly wet soil at the edge of a natural pond. Most prefer no more than 5-8cm (2-3in) of water above their roots.

In ponds without planting shelves or pockets, you can raise planting containers on bricks to the re-quired depth.

Perforated plastic baskets are also ideal for marginal plants but you can use ordinary flowerpots. Choose a container size that matches the rootstock and prepare the plants as before, removing dead leaves.

Marginal plants with creeping rhizomatous roots, such as bog arum (Calla palustris), should be planted horizontally with the growing shoots exposed. Clump-rooted marginals, such as flowering rush (Butomus umbellatus), or tuberous-rooted types like arrowhead (Sagittaria sagittifolia) should be planted vertically, with the base of the shoots at the soil surface. Cover the soil mix with pea shingle before lowering under water.

Planting oxygenators

Oxygenating plants, which supply oxygen (vital to pond animals), grow almost entirely underwater. They also provide shelter and a spawning ground for fish. Oxygenators are often sold as unrooted cuttings. If there is no soil in the pond bottom, plant them in a small perforated container filled with aquatic or loam-based soil.

Introducing floating plants

Simply place floating water plants, such as frogbit (Hydrocbaris mor-sitsranae), and water soldier (Stratiotes aloides), on the water surface. They get their nourishment through trailing roots and foliage which absorb nutrients directly from the pond water.

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