These have floating leaves and flowers and thick tuberous rootstocks anchored in mud at the base of the pool. The nymphaeas (water lilies) are the most important of these, with about seventy species and varieties hardy in this country and suitable for pools of various depths. When making a selection it is important to bear the last in mind and to pick varieties from the right group.
All hardy water lilies need a stiff compost; fibre-free loam enriched with one sixth part well-decayed cow manure or a half pint measure of bonemeal to each bucketful of soil. The compost should be used in a moister condition than is usual for pot plants, otherwise it will not bind and the roots may float upwards. Covering the soil after planting with 1 in. of washed shingle prevents fish from rooting in the mud and making the water cloudy.
There are two main groups of hardy water lilies; one with rhizomatous roots and the other with upright-growing tubers. The last, which includes the British native Nymphaea alba, should be planted perpendicularly, with its black and white feeding roots well spread. It should be noted that any thick white roots present are old anchorage roots and useless to the new plant. These should be removed.
Rhizomatous lilies like the North American N. tuberosa and N. odorata should be planted horizontally — like bearded irises, which they somewhat resemble. Most members of this group have fragrant flowers.
The following water lilies will grow in water 20 to 30 in. deep (less if there is room) and in time should each cover a surface area of approximately 5 to 6 sq. ft.
In this group the variety gladstoniana is superb, with large cup-shaped flowers of glistening white, the centres filled with rich golden stamens. The dark green leaves are tough, with a polished texture. Other good whites are Gonnere, a semi-double, the squat blooms wrapped around with olive-green sepals and N. tuberosa richardsond of globular habit. The only fully double water lily Gloire de Temple Sur Lot is suitable for 18 to 20 in., but is not as free flowering as many others. The creamy-white petals of the flowers curve like those of an incurved chrysanthemum.
Among the pinks colossea is flesh coloured; tuberosa rosea, soft pink; Marguerite Laplace, deep rose, and Mrs Richmond, deep pink. Marliacea carnea and marliacea rosea— soft and deeper pink respectively — were given his own patronymic by the great French breeder Latour Marliac — a sure indication of their worth.
There are several good reds in this group, particularly the prolific Escarboucle, a wine-red sort with flowers up to dinner-plate size and, excepting for Wm Falconer, the deepest in colour. Gloriosa is a fine red for the shallower depths in this section, also the adaptable and free-flowering James Brydon which produces masses of squat carmine-red blooms throughout the whole of the summer Colonel Welch is the most robust yellow, but less fine than those recommended in the next section.
The medium growers are suitable for 12 to 18 in. of water and cover a surface area of approximately 4 sq. ft. in time. They are thus ideal for small pools and gardens.
Among the whites are Albatross, a very shapely sort; caroliniana nivea, sweetly scented and very prolific, and Hermine, whose stellate flowers stand clear of the water.
Fire Crest is a fragrant pink sort with red-tipped stamens which look as if they have been touched by flame, but laydekeri lilacea, rosy lilac, and laydekeri purpurata, rosy crimson, are two of the most reliable with only medium-sized blooms but prolifically produced.
Livingstone is bright red flecked with white; Masaniello, deep rose, and Paul Hariot changes colour with age — the new blooms being apricot yellow which gradually deepens to orange red. Two good yellows in this section are marliacea chromatella, of a soft primrose shade with chocolate-blotched leaves, and Sunrise, which is semi-double with deep golden flowers.
There are also several miniatures for rock garden pools. These may need protection or lifting in winter and they can also be grown in small containers on a sunny windowsill indoors. N. tetragona (pygmaea alba) is white with green leaves, and pygmaea helvola, soft yellow with chocolate-blotched foliage.
Other Deep Water Aquatics
Nuphars or pond lilies are strong-growing aquatics allied to but inferior to nymphaeas. Their only advantages over the latter lie in an ability to grow in shade, deep or running water — situations which are anathema to the true water lilies. If used at all in ornamental pools, the roots must be confined and only the weaker sorts like Nuphar pumila ( N. minima), with pale yellow flowers; N. japonica rubrotinctum, cup-shaped orange flowers with red-tipped stamens, or N. japonica variegatum, which has cream-splashed foliage, should be grown. Plant them the same way as nymphaeas.
Nymphoides peltata ( Limnanthemum nymphoides), the water fringe, has poppy-like, three-petalled flowers of golden yellow and crinkly edged, almost round, chocolate-blotched, floating leaves. It grows in long strands across the water surface, shading the depths beneath and so discouraging algae, but is easily pulled out if it becomes too rampant.
Aponogeton distachyus, the water hawthorn, takes its name from the vanilla-like scent of the black and white, forked flowers. These float, as do the long narrow leaves. It will grow in depths of 12 to 20 in.
