Water Garden Plant Types

In Deep and Shallow Waters

Water can be used as a medium in which to grow a quite different range of plants: aquatics actually in it, and bog plants in the wet soil immediately around it. They are not incompatible with the mirror effect provided they are not permitted to cover the whole surface, but they are incompatible with crystal-clear water which can only be maintained by constantly changing the water in the pool or by treating it with chemicals to prevent algae living in it and clouding it.

Really you need to make a broad choice at the outset between pools with plants and pools without them, water that is still and water that is in movement.

You can also use water in formal or informal stretches — in regularly shaped basins, canals or rills, which are often very suitable near the house, on a terrace or in a rose garden, or in irregularly curving pools that appear to belong naturally to the site. Informal pools are often associated with rock gardens, and they can be used just as effectively in wild or woodland gardens or indeed in any setting that is not itself regular and geometric. If water lilies are to be grown, place your pool where it gets sunshine for much of the day; without it the flowers will not open.

In small gardens, streams are often more of a problem than pools since they do need to appear natural and that rather presupposes that they will follow the correct contours of the land, which is not always where they are wanted. Yet to confine streams too obviously to the higher ground where they have to be retained by embankments can look silly.

Plastic (PVC) or butyl rubber liners have almost entirely replaced concrete or puddled clay as a means of making pools watertight. Liners should be obtained sufficiently large to cover both bottom and sides and overlap sufficiently to be tucked into the soil or hidden beneath turf, rocks or paving slabs.

A more expensive alternative is to use fibreglass, a far more rigid material which must be preformed to the required shape. Fibreglass pools of many sizes and designs are offered by specialist water-feature firms and by many garden centres. They are the simplest way to make a pool since all you need to do is choose your pool and then dig a hole large enough to accommodate it.

With plastic or rubber liners you determine the form of the pool yourself and excavate the soil to this design. Formal pools often have vertical or very steep sides but for informal pools it is preferable to prepare a dish-shaped hole with shallowly sloping sides. This is partly because it is a very trouble-free shape, with the weight of the water holding the liner firmly down, and partly because it is a natural shape which looks right and gives plenty of scope for planting in different depths of water according to the needs of the plants. As a rule a depth of 60cm (2ft) in the middle of the pool is ample and 45cm (lift) will suffice for most aquatics. Marginal plants vary in their preferences from water about 8cm (3in) deep to none at all, simply wet soil for their roots.

The surface on which the waterproof sheet is to lie should be smooth and free of sharp stones or other rough objects which might damage it. Rake the soil or flatten it with the back of a spade or spread some sand over it. When the sheet has been roughly laid in position (or PVC, which is very flexible, stretched across the pool like a limp drum cover) lay a few stones or turves around the edges to hold it in position, and run in some water. Its weight will stretch and settle the sheet securely on the bottom and sides of the pool. Once the liner has settled, you can cover the edges with soil, turves, rocks or paving slabs. Streams can be lined in a similar way but if they wind and twist and tumble over cascades or waterfalls they are liable to tear, and it may be easier and more satisfactory to line them in the old-fashioned way with concrete. Preformed fibreglass sections for streams and cascades are available but it is difficult to disguise them satisfactorily and some parts tend to protrude awkwardly when the job is done. Concrete can be spread easily where it is required, with rocks actually bedded into it where this seems desirable.

When you come to prepare the bottom of your pool for planting, you can spread soil all over the liner or concentrate it in mounds here and there. Easier still is to plant in plastic baskets which can be purchased from any dealer in aquatics. The procedure is exactly as if you were potting the plants, and you can do it comfortably indoors, after which you just sink the baskets in the pool wherever you want them. When the plants grow too big or are otherwise in need of attention, the baskets can be fished up, and the soil in them renewed if necessary, and they can go back with a minimum of fuss.

Mid-April to mid-June is the best season for planting aquatics, but when they are sold in containers, as many are nowadays, they can be moved like other container-grown plants at almost any time provided their roots are not unduly disturbed. Some kinds float freely in the water and require little or no soil. They can be planted by simply dropping them into the pool. These submerged aquatics are useful as protection for fish and to supply oxygen to the water which, on warm days, can be seen rising in bubbles from their leaves.

Fish are not really an appropriate topic here, but it is important that they are not introduced until plants are growing freely in the water.

If the garden has a natural stream or spring, no other form of circulation need be considered, and if the stream has sufficient flow it may even be possible to make it operate a ram to raise water to a higher level from which it can flow into fountains or over waterfalls and cascades. Most gardeners possess no such facilities and if they want moving water at all must seek other means to obtain it, either from a mains supply, which is expensive and bad for plants, or by recirculating it with a pump. Small submersible electric pumps are available for this purpose and usually provide the best solution.


Water Garden Plants

Aruncus sylvester

Goat’s beard. Creamy plumes appear in early summer. A variety named ‘Kneiffii’ has finely divided leaves. For boggy soil.



False goat’s beard. Shorter than aruncus and with more cone-shaped plumes of white, pink or crimson flowers. Also suitable for damp soil but not actually for growing in water.



Marsh marigold, kingcup. The commonest species, Caltha palustris, grows wild in Britain and has flowers like huge buttercups. There is a double-flowered variety named ‘Flore-pleno’ which is even more effective. Another species from the Caucasus has even larger flowers and is called Caltha polypetala. All like the very damp soil at the edges of pools and streams.



Spiraea-like plants of which one species, Filipendula ulmaria, is the British meadowsweet with plumes of creamy flowers in summer. There is a yellow-leaved variety named ‘Aurea’ and another with double flowers named Floreplena’ . Other species are Filipendula palmata, pale pink; Filipendula purpurea, rosy-purple and Filipendula rubra, pink. All are for damp soil.



There are numerous kinds including all the varieties of Iris sibirica and Iris kaempferi as well as the common yellow flag, Iris pseudocorus, in both its green and white variegated forms and the tall creamy white Iris ochroleuca, all of which can be grown in damp soil beside pools. Iris laevigata prefers to grow in shallow water and is available in light blue, dark blue, pink and white varieties.



Skunk cabbage. The popular name refers to the very large leaves and the rather heavy smell of this handsome plant with arum-lily flowers in spring. These are yellow in Lysichitum americanus, the most vigorous kind, and white in Lysichitum camtschatcensis. Both are for wet soil or very shallow water.



Yellow loosestrife, creeping jenny. The two popular names distinguish plants of very different character. The yellow loosestrife, typified by Lysimachia punctata and Lysimachia vulgaris, make big clumps of erect stems bearing yellow flowers in summer. The creeping jenny, Lysimachia  nummularia, trails flat on the ground and also has yellow flowers and an attractive yellow-leaved variety named ‘Aurea’. All are for moist soil.



Purple loosestrife. Two kinds, Mimulus salicaria and Mimulus virgatum, both have slender spikes of magenta flowers. They like moist soil.



Monkey flower, musk. Several kinds, including Mimulus cupreus, yellow and brown; Mimulus cardinalis, scarlet; Mimulus luteus, yellow spotted with pink, and Mimulus tigrinus, yellow, pink and crimson, all grow well in wet soil.



Water lily. There are many species and hybrids, differing in vigour and colour, from white, pale yellow and pink to crimson. All have heart-shaped, floating leaves with the flowers seeming to rest on them. The flowers are only open during the middle part of the day.

Their depth of water requirement varies from 8cm (3in) for small kinds, such as Nymphaea pygmaea and its varieties, to a minimum of 30cm (12in) for big kinds, such as ‘Escarboucle’, ‘James Brydon’ and the varieties of Nymphaea laydekeri and Nymphaea marliacea.


Osmunda regalia

Royal fern. Upstanding yellowish green fronds. Likes wet soil.


Pontederia cordata

Pickerel weed. Broadly lance-shaped leaves on long stalks and spikes of blue flowers in July and August. Likes shallow water.



Primrose. A number of primulas thrive in moist soil. These include all the ‘candelabra’ species, so-called because they carry their flowers in successive tiers of diminishing size.


Examples are Primula aurantiaca, Primula japonica, Primula pulverulenta, Primula helodoxa, Primula beesiana, Primula bulleyana and Primula cockburniana. Also suitable are Primula sikkimensis and Primula florindae, with heads of dangling yellow flowers, and cluster-flowered species such as Primula denticulata, Primula capitata and Primula vialii.


Rheum palmatum

An ornamental rhubarb with large, red-tinted leaves and crimson flowers. Likes moist soil.



Several kinds are available, including Rodgersia aesculifolia, Rodgersia pinnata, Rodgersia podophylla and Rodgersia tabularis. All like moist soil. They have large, umbrella-like or deeply divided, bronzy-green leaves and branched clusters of small pink or white, spiraea-like flowers.


Sagittaria sagittifolia

Arrowhead. The popular name refers to the shape of the leaves. The white flowers are borne in spikes and are double in a variety named ‘Fiore Pleno’. Likes to grow in shallow water.


Scirpus tabernaemontani ‘Zebrinus’

Porcupine quill rush, zebra rush. The popular names well describe this striking foliage plant which has long quill-like leaves banded with green and white. It likes to grow in shallow water.

15. April 2011 by admin
Categories: Plants, Water Features, Water Garden Plants | Tags: , , , , | Comments Off on Water Garden Plant Types


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