Aquatic Plants for the Garden Pond
There are manythat grow in deep water. Their roots need and this is best kept in a container, allowing the plant to be lifted out of the water for pruning, treating for and for feeding. The container can be a box, pot, basket or a proprietary plastic container. The soil should be plain with the addition of bonemeal; some charcoal lumps will help to keep the soil sweet.
Some plants float on the surface with trailing roots that pick up nutrients from the water and these can be easily lifted out and thinned if they spread too far.
Marginal plants in the main have their rootstocks just under the water with their leaves and flowers held well above the surface. Here again, containers should be used to allow the plant to be lifted out, thinned and stopped from taking over the pond. Many aquatic plants are invasive.
A group of plants of which A. calamus (1), which comes from wide areas in the Northern Hemisphere, and A. gramineus (2) from Japan are the two most popular. A. calamushas sword-shaped leaves like an iris and flowers that are densely packed on short spurs more like an arum. It reaches a height of about 60-75cm (24-30in). A. gramineus is finer with narrow leaves and reaches only 20-30cm (8-12in) tall. A variegated variety is available.
Two varieties are grown as, A. lanceolatum and A. plantago-aquatica. These similar plants both originate in the Northern Hemisphere and grow to 15-30cm (6-12in) tall. Spikes of small pink flowers rise above the oval leaves. This plant is quick to establish in the pond.
This South African plant is very decorative, with oblong floating leaves and spikes of scented flowers that rise above the water surface. A distachyus is the hardiest of the family and flowers from early spring to late autumn. This adaptable plant can be grown from tubers or from seed and will thrive in very shallow water or as deep as 45cm (18in).
Azolla caroliniana and A. filiculoides are two very similar plants native to South America. They are floating plants that form mats of fine fronds on the surface, with the roots taking nourishment from the water. The leaves turn from a fresh green in summer to reddish autumnal tints. In severe climates they are best over-wintered in a pan and kept frost-free.
Native to Europe and Asia, this plant is equally at home in marshland, shallow or deep water. It has long thin green leaves, triangular in section, and bears up to 30 pink or purple flowers in each flowerhead that arise like inverted umbrellas from early summer to early autumn. The plant can reach 1.2m (4ft) tall.
Found in the wild in North America, Northern Europe and Asia, this plant has dark green heart-shaped leaves and a creeping rootstock that grows happily in and out of the water. It can be propagated by dividing the roots into sections. The white flowers resemble those of the Arum Lily. After pollination by pond snails, the female flowers mature to red berries. It grows to about 15-20cm (6-8in) in height.
Kingcup; Marsh Marigold
Native to North America and Europe, these plants have round serrated leaves and buttercup-like flowers of a golden yellow. The single forms can be grown from seed or root division. Varieties to look for are C. Atoa (white), C. palustris, C. polypetala and the double form C. palusths plena. They grow in shallow water or wet mud and vary in height from 20cm (8in) to 90cm (3ft), depending on variety.
These perennials from Europe are grass-like and most are very invasive; they should be contained to prevent their spreading. C. riparia ‘Bowles’ Golden’, with golden leaves and brown flowers, is recommended as being the least invasive of the genus. It grows to over 30cm (12in) tall.
From Chile and Europe, these sedge-like plants bear clumps of green or brown flowers arranged on stems like an umbrella. C. eragrostisis normally hardy and about 60cm (2ft) tall while C. longus is hardier but very invasive; reaching up to 1.2m (4ft) in height. The dark green stems of C. longus provide excellent cut material for use in flower arrangements. They should not be grown in deep water.
These plants from North America and Europe have oval leaves on long stems and bur-like heads; these should be removed to prevent seeding. Flowers are white or pinkish white. E. ranunculoides grows up to 45cm (18in), E. radicans(not hardy in severe climates) to 1.2m (4ft), and E rostratus (Burhead) to 30cm (12in).
A prolific species from the tropics, this plant is suited to areas subject to frost as this kills the plant before it can become too invasive. Roots should be lifted and kept just moist from early autumn to late spring and then floated again in the pond during the summer. The leaves are heart shaped and the lilac flowers, borne on spikes up to 38cm (1 Sin) high, are spectacular. The plant spreads to 45cm (18in) wide in one season.
Bog Cotton; Cotton Grass
A wild plant in the Northern Hemisphere, this genus has grass-like leaves and cotton-like seedheads. E. angustifolium grows to 30cm (12in) tall, E. latifoliumXo45cm (18in)and E. vaginatum barely reaches 30cm (12in). All thrive in shallow water or wet mud and can be grown from seed or by root division.
Glyceria aquatica variegata
A European plant with grass-like leaves arranged in clumps and striped in white, yellow and green with a pink hue in spring and autumn. It will reach 90cm (3ft) if unrestricted but will be only a third of this height if it is grown in a smallish container. Propagate from side shoots.
From the mountainous regions of the Himalayas through to Japan, this attractive plant has heart-shaped, blue-green leaves, red stems and white flowers with a large central cone. It grows in shallow water and will reach 45-50cm (18-20in) tall. Increase by root division. A double form, H.c. Plena, is available.
A floating plant from Europe with bright green, fleshy, kidney-shaped leaves and small white flowers with three petals. Snails and water beetles enjoy the foliage. Terminal buds drop to the bottom of the pond in the autumn and sprout in the following spring; the rest of the plant decays.
A European plant up to 30cm (12in) tall that makes a good marginal specimen. It has dense rounded foliage and creeping stems covered with fine downy hair. The flowers are yellow and appear in late summer. Increase by dividing the roots.
Iris; Yellow Flag
A large family of plants with members from many parts of the world: a few thrive in wet conditions. I. kaempferi enjoys summer wetness but needs to be dry during the winter; it is best grown in a container that can be removed from the water on to dry land in the autumn and replaced in the spring. The flowers appear in midsummer on stems up to 90cm (3ft) tall. Many varieties are available with single or double blooms in shades of blue, lavender, purple, pink and white. The ‘Higo’ strain is particularly beautiful. I. laevigata enjoys water all the year, producing blue or white flowers. I. pseudacorus revels in water up to 45cm (18in) deep, bearing superb yellow flowers on stems up to 1.5m (5ft) high in early summer. I.p. ‘Variegata’ has yellow flowers and yellow-striped foliage. I. versicolor, an American plant, produces violet-blue blooms in early summer on 60cm (24in) stems. The lovely variety ‘Kermesina’ has wine-red flowers in early summer. All these irises can be increased by dividing the rhizome after flowering.
A large family spread throughout the world, but only a few species are recommended for the garden pond as they are invasive; all have grass-like leaves. J. bufonishas reddish flowers and grows to 20cm (8in) tall. J. effususvar. Spiralis (4) has curious spiral green stems reaching 45cm (18in) in height and J. ensifolius has dark brown to blackish flowerheads held 30cm (12in) high. Ail enjoy either shallow water or moist soil. Be sure to avoid the invasive species.
A European plant with both bright green and brown aromatic leaves, that grows well in either moist soil or shallow water. The lavender blue flowers are borne in clusters. It normally grows to 30cm (12in) tall, but in rich soil it can reach 1 m (3.3ft). Increase by division of roots.
Bog Bean; Buck Bean
A Northern Hemisphere plant with light green trifoliate leaves and spikes of rosy white flowers in early summer. It spreads by means of a horizontal rootstock, which makes it suitable for covering pond edges; it grows only about 30cm (12in) tall. Keep this plant constricted and cut it back if it is too vigorous for its chosen site.
Monkey Flower; Monkey Musk
A group ofand perennials, mostly from North America; they flower in late summer with red, yellow and orange blooms. M. guttatus grows to 45cm (18in) tall with single yellow flowers blotched with crimson. The ‘hose-in-hose’ varieties have semi-double flowers. M. cupreus, M. lewisii, M. maculosus, M. moschatus, M. ringensand M. tigrinusarea worth growing. They vary in height from 20cm (8in) to 90cm (3ft).
Hardy Sugar Cane
This American plant, up to 1.8m (6ft) tall, has the appearance of an ornamental grass and bears flowers noted for the groups of silky hairs at their bases. M.s. Variegata has white and green variegated foliage.
A plant from Europe with many historical and legendary associations. It is ideal for the pool edge, reaching 20cm (8in) tall and bearing bright blue flowers. It seeds well and thrives even in the shade. An improved version, ‘Mermaid’, has larger and brighter blue flowers. An excellent choice.
Yellow Water Lily; Spatterdock
These water lily-like plants from North America, Europe and Japan have both submerged and floating leaves; the submerged ones are finely divided, the floating ones oval and leathery. The plants have a creeping rootstock and bear yellow flowers from late spring to early autumn. All grow well in deep and shady water. Some varieties are very vigorous and should be controlled by using containers. For small ponds choose the free-flowering Nuphar minima.
Nymphoides peltata (Villarsia nymphoides; Limnanthemum peltatum)
Floating Heart; Water Fringe
A lily-likewith rounded floating bright green leaves with crinkled edges. The flowers are yellow, blooming in later summer and held just above the water surface. It will grow well in either deep or shallow water and should be kept in a container to curb its invasive nature.
A North American plant with strap-shaped floating leaves in deep water; in shallow water the leaves stand up to 45cm (18in) above the surface. They are dark blue-green on the upper surface and silver on the undersides. The flowers appear in spring and early summer, yellow in colour and borne on conspicuous white stems. Grow from seed in shallow water and then transplant to deeper water or to soil.
There are two North American species, P. alba and P. virginica. The former has arrow-shaped leaves and white arum-like flowers followed by red berries; the latter has green flowers and green berries. Both grow up to 75cm (30in) in height and can be increased by dividing the rootstock.
A marshland plant from North America, P. cordata has shiny heart-shaped deep green leaves and bears blue flowers in late summer. The plant will make large clumps, but they are easily split for smaller areas. It grows up to a height of about 60cm (2ft). A less hardy species, P. lanceolata, has longer lance-like leaves and can reach 1.5m (5ft) in height.
Ranunculus lingua grandif lora (6)
An improved form of a European plant, with narrow leaves and large yellow flowers similar to those of the buttercup; these appear in late spring and summer. It grows to a height of 90cm (3ft) and can be increased by dividing the rootstock. The stems are thick and deep pink in colour. Contain the roots to stop the plant spreading too far and taking over the pond.
These plants from Europe and Asia are not generally recommended for a small pond; S. sagittifoliaan6 S. japonica florepleno are the two that are suitable; the former needs a container to prevent it spreading. They have distinctive arrow-shaped leaves and white flowers in midsummer. Up to 45cm (18in).
From North America comes Saururus cernuus and from China and Japan, S. chinensis. These plants have dark green heart-shaped leaves and sprays of scented flowers in summer; the former white, the latter cream. Both can reach 45cm (18in) tall.
Apart from two varieties, these plants should not be used as they are too invasive. Even these two should have their roots contained to prevent them from being too vigorous in growth. S. albescens has white variegations on the narrow green leaves; it will reach 1.2m (4ft) tall. S. tabemaemontanii var. zebrinus(Porcupine Quill Rush; Zebra Rush) has green and white bands on the stems and grows to 90cm (3ft) high. Increase both by root division in the spring.
A floating plant, found wild in Europe, with sword-like leaves radiating from a central crown. The flowers are small and white; after flowering the plants sink under the surface and produce side shoots that lie dormant until the following spring. Water Soldiers grow to 30cm (1 ft) across and prefer alkaline water.
A North American plant with spear-shaped leaves and long spikes of deep purple flowers. In mild areas it can be left to overwinter in the pond, but it requires protection from frost. If in doubt, lift the plants and keep them under cover until late spring. It can grow to 1.8m (6ft) tall in good conditions and can be increased by dividing the rootstock.
This annual floating plant from southern Europe has triangular serrated leaves of a bright glossy green. The flowers are small and white and the black seeds (nuts) are large with four spines, and edible. They can be left to ripen on the plant and germinated the following spring.
These European plants are commonly and erroneously called bulrushes because they have tall grass-like leaves and distinctive brown heads of flowers. They are very invasive and only two are suitable for the garden pond: T. angustifolia, which reaches 1.2m (4ft) high, and T. minima, which is smaller in scale and only grows to 45cm (18in) tall. Increase both by root division.
Floating Heart; Water Fringe
This plant is described under its alternative name of Nymphoides pelfafa.
Arum Lily; Lily of the Nile
From Africa, this plant has glossy green leaves and spectacular white flowers during the summer months. It grows up to 90cm (3ft) in height. The true flowers are tiny and yellow, and massed on a central column, or spadix, which is partially enclosed by a showy white modified leaf called a spathe. The plant needs some protection from winter frosts, although hardy varieties are being introduced. One of these is ‘Crowborough’. Provide plenty of water during the growing season in spring and summer and increase by dividing the rootstock.