Ferns and Foliage Plants for Garden Ponds
Foliage is as important a part of the ornamental garden as. Leaves in all their shapes and forms add interest, subtle variations of colour, and provide a foil for flowering subjects. In many ways foliage plants are more important than flowering ones, for they make a background or a backbone to a feature. With careful use they can also be used to frame a picture or create a focal point. The possibilities they offer are limitless and as they provide this service for much of the year they should be duly recognised.
Ferns, of course, are the cream of foliage plants. Most enjoy damp conditions and partial shade, but a few will flourish in really wet conditions in the open. They’ have a preference for slightly acidrich in organic matter and this can be adequately catered for by incorporating liberal quantities of peat at planting time.
Osmunda regalis (royal fern) is without doubt the finest of all hardy ferns. A tall regal plant with large, leathery fronds between 1- 2m high. These are lime green, but turn a rich burnished bronze in the autumn before collapsing on top of their large scaly crowns. This debris, together with a handful of straw or bracken, should be placed over each crown in order to protect the young fronds as they emerge the following spring.
It is a matter of some regret that many gardeners will be unable to find sufficient space for this marvellous plant. However, its varieties ‘Undulata’, with crimpled and crested fronds, and the strangely tassellated ‘Cristata’ (crested royal fern) are generally of more manageable proportions. Even the superb purplish-fronded Purpurescens’ seldom grows as large as Osmunda regalis.
Onoclea sensibilis (sensitive fern) can be grown in many situations as it attains a height of little more than 45cm and enjoys both damp and aquatic conditions. It can be used in much the same manner as Cyperus longus or Lysimachia nummularia, being planted in moist soil at the poolside and allowed to colonise the shallower areas. In texture and shape the fronds of onoclea have a lot in common with osmunda, but rather than growing from a scaly clump they are spread out along a black creeping rhizome. During early spring the fronds are an attractive rose-pink colour, but fade with age to pale lime green.
Matteuccia struthiopteris (ostrich feather fern) is a handsome creeper too, thrusting up bright green fronds arranged in a shuttlecock fashion around a hard scaly rootstock. Like onoclea, this will grow in extremely wet conditions in either sun or shade. It is a good bit taller though, mature plants being almost a metre high and obviously in need of careful placing.
Most of the other ferns that enjoy wet conditions are less spectacular, but can be used for carpeting between other plants. I am thinking now of the short growing Dryopteris cristata (crested buckler fern), the elegant Dryopteris palustris (marsh buckler fern), and that classy North American woodlander Woodwardia virginica (Virginian chain fern).
Few other foliage plants are in the same class as ferns, except possibly the hostas. Not that they resemble ferns in any way, for they have broad, glossy, ovate or cordate leaves in innumerable shades of green, or sometimes variegated and occasionally edged with cream. Unlike ferns they produce moderately attractive bell-shaped flowers of lilac or white in graceful arching sprays.
It is a brave man who tries to separate and classify the various species and varieties of hosta. Even the botanists do not always seem able to agree. So what I will do here is describe the popular kinds under the names they are usually sold by, even though these may not strictly speaking be botanically correct.
Hosta undulata medio-variegata is probably the most commonly cultivated sort. A striking plant with slightly twisted leaves in a mixture of cream and green. Another unrelated hybrid called ‘Thomas Hogg’ has large, plain green leaves broadly edged with white, while the cultivar ‘Aurea’ sports golden foliage that fades to green with age.
But for texture and shape the plain-leafed kinds are unsurpassed. Particularly if one looks at species like Hosta sieboldiana with its immense glaucous leaves 30cm long and almost as wide, or the elegant Japanese Hosta fortunei proudly displaying narrow, bright green leaves and graceful sprays of pale lilac blossoms. Hosta plantaginea produces big, pale green, heart-shaped leaves and surprisingly attractive fragrant white flowers during July and August. Certainly if you only have room for one hosta, then this must be it. For it can justify its place by either flower or foliage alone.
Foliage is unquestionably the principal attribute of the various decorative members of the rhubarb family. These are specimen plants for a focal point and useful in creating bold architectural effects. Rheum palmatum is unquestionably the best and will tolerate really wet conditions. It is also the most impressive species with expansive fresh green foliage and spikes of creamy blossoms of 2m high. Its cut-leafed form tanguticum has a purplish infusion and attractive deeply cut foliage, while ‘Bowles’ Crimson’ is of typical form, but with spires of crimson flowers and leaves with a strong purplish-red cast.
It would be difficult to write about foliage plants for the bog garden without giving Gunnera manicata a mention, even though it is much too large for most gardens. Being the largest herbaceous subject capable of cultivation outdoors in Great Britain, and with its immense rhubarb-like foliage it can create quite dramatic effects. When growing contentedly it will produce leaves up to 1.5m across on stout prickly leaf stalks some 2m high. Its strange inflorescence is like a large reddish-green bottle brush and appears beneath the foliage during late summer.
A native of Brazil, gunnera is reliably hardy in most localities, but during autumn benefits from having its withered leaves inverted over the huge scaly buds into which it retreats during the winter. If you think you can find a place for this gentle giant, refrain from planting until the spring so that it has an opportunity to develop a good root system before the winter.