Plants for the Pond: Sedges, Reeds and Rushes
To the newcomer to, one rush may seem very much like another, and sedges and reeds pose considerable problems as it is difficult to decide where one starts and the other ends. Broadly speaking, sedges are the grassy marginal plants with small, congested, grass-like seed heads, while rushes generally have cylindrical foliage and reeds broad, fleshy leaves. This is technically how they are separated, but our forebears were obviously not aware of these subtle differences and popular names which are, strictly speaking, incorrect have attained wide popularity. In practical terms we may consider that all plants described under this heading have vertical grassy foliage which is their main attribute, their flower spikes being of secondary or little importance.
Mention water plants and bulrushes always spring to mind, those stately plants with broad, glaucous-green foliage and chocolate-brown, poker-like fruiting heads. But these are not really bulrushes, for the true bulrush is Scirpus lacustris. These are reed maces.
There are a number of reed maces to choose from, but unless there is plenty of room to spare the native Typha angustifolia and Typha latifolia should be avoided. I would never grow them in a pool lined with polythene either, for they spread by creeping rhizomes which have sharp, spear-like growing points capable of puncturing a liner. Indeed, the cultivation of these two lovable rogues is beset with problems as they are both too vigorous and too tall for most situations. When grown in the comparative safety of a basket they continually topple over, and if given full rein on the marginal shelf will interfere with their neighbours.
For a really good, well-behaved reed mace we must turn to Typha laxmannii which in most nursery catalogues still languishes under the outmoded name of Typha stenophylla. This grows little more than a metre high and has slender, willowy leaves and attractive, rich brown pokers. But in the smaller pool this is still too large and is better replaced by Typha minima. Rarely exceeding 45cm in height, this complete miniature could have come straight out of Lilliput. It has somewhat grassy foliage of a bluish-green hue and short, chunky flower spikes.
The true bulrush, as represented by Scirpus lacustris, is a rather demure character with slender, dark green, cylindrical, needle-like stems a metre or more high and tiny, pendant tassels of reddish-brown. It is useful as a foil for more cheerful aquatics and can be used to good effect in creating height in a formal scheme. But I would always go for the steely-blue Scirpus tabernaemontani as it has more substantial foliage with an attractive mealy bloom.
Not only is Scirpus tabernaemontani a better looking plant, but a progenitor of two of the finest foliage aquatics. The cultivar ‘Zebrinus’ (zebra rush) is the most striking as it has foliage alternately barred with green and white. As with most variegated plants green stems are occasionally produced and these must be removed immediately they are noticed to prevent them outgrowing the variegated part.
The variety ‘Albescens’ is also attributed to Scirpus tabernaemontani, although there is considerable speculation as to its origin. Certainly it has the same pleasant habit, but with lovely sulphureous-white stems conspicuously marked with thin longitudinal stripes of green. It does not appear to be as hardy as its colleagues, so the old stems should be bent over the crown for the winter and a generous layer of bracken or straw secured over it as well. In fact, if it is growing in a basket and can be easily removed intact from the pool, it can be stood in a cool, frost free shed and just kept moist until the following spring without coming to any harm.
The various species of juncus are of similar habit to scirpus, but generally much shorter growing and owing to their prolific seeding and creeping capabilities, excluded from the garden pool. Two mutants of the native Juncus effusus (soft rush), however, are worthy of attention and in common with the majority of choice garden plants, rather slow to reproduce.
The most interesting mutant is Juncus effusus ‘Spiralis’ a curiously malformed plant with slender cylindrical stems which grow in a corkscrew fashion such as is seen in the corkscrew willow, Salix matsudana ‘Tortuosa’. The other is a golden and green barred version of the species known variously as ‘Vittatus’ and ‘Aureo-striatus’. Unfortunately, this is a very weak grower which is easily overtaken by its plain green foliage and is in constant need of attention.
When variegated foliage is required in a plant that has vigour and seldom throws unwanted green shoots, then Glyceria maxima variegata provides the answer. Strictly speaking, this does not belong here as it is really a grass, but its overall aspect is the same as a rush or sedge and it certainly serves the same purpose. It is a handsome plant, tolerant of damp conditions or up to 15cm of water and has cream and green striped foliage which is infused with a deep rose flush during early spring.
The variegated form of Acorus calamus has the same deep pinkish infusion in its emerging shoots, but foliage which ultimately attains the character and proportions of an iris. Again, this is not strictly speaking a rush or reed, although most gardeners would allow those terms to embrace it. It is, in fact, a rather bizarre member of the arum family with tiny, greenish, hornlike inflorescences which appear amongst the leaves. These are of little significance and can be barely discerned amongst the shiny fresh green foliage of ordinary Acorus calamus. Despite the flowers being of little consequence, both Acorus calamus and Acorus calamus ‘Variegatus’ are well worth growing, not just for the handsome appearance of their foliage, but its rich tangerine fragrance.
This is not apparent in the smaller kinds which are grown variously under the names of Acorus gramineus and Acorus pusillus. These are dwarf species with slender, dark green, sword-like leaves no more than 25cm high which, in the variegated kinds, are boldly striped with yellow. They are neat clump-forming plants and ideally suited to the rock pool or sink garden.
A lot of confusion exists amongst these as to which are distinct species and which are mere variants, but this has not spread itself into the nursery trade and the pool owner who buys a plant under either Acorus gramineus or Acorus pusillus is almost certainly purchasing a dwarf kind of exceptional merit.
No one is likely to get into a muddle over the status of Butomus umbellatus (flowering rush), as this striking plant is the sole member of the family with no forms, variants or allied species. It is a quite unique plant with narrow, triquetrous foliage interspersed during late summer with spreading umbels of dainty rose-pink blossoms. These are often in evidence at the same time as the soft blue flower spikes of Pontederia cordata and a mixed planting of these two is something to behold. Not only are the pastel shades of their flowers complementary, but their contrasting leaf growths make a remarkable combination.
Eriophorum angustifolium (cotton grass) is another plant which can create an effect. Not necessarily in association with any other species, for with its stiff grassy foliage sprinkled in early summer with silky, cotton wool-like, seeding heads, it is a picture in itself. Upwards of twenty different species of eriophorum have been described, but only Eriophorum angustifolium and the more mundane Eriophorum latifolium are cultivated. Both require acidicand water if they are to flourish and seem to prefer a position out of full sun.
The sedges prosper under almost any conditions, particularly the native kinds like Carex pendula. This tall and dignified plant with broad green leaves and pendulous, brownish, catkin-like flowers is particularly useful for filling an inhospitable corner in the larger water garden. For the small pool it has little use and is better replaced by one of the cultivars of Carex riparia such as the rich golden-yellow ‘Bowles’ Golden’ or the striking green and white ‘Variegata’. To be truthful few of the carex species have much to offer the modern water garden, and although a number are offered by aquatics specialists, none other than those described should be afforded a position. There are many more far superior leafy marginals.
A prime example is Cyperus longus (sweet galingale). A larger and coarser version of the popular florist’s umbrella plant (Cyperus alternifolius), this is invaluable for interspersing as a pleasant foil amongst more colourful subjects. Where moist ground reaches down to the pool it can really be exploited, for Cyperus longus is never happier than when marching into the pool from damp ground. In a natural pool where erosion is a problem then cyperus is the perfect stabiliser.
It is not bad looking either, with terminal umbels of stiff, spiky leaves which radiate from the stem like the ribs of an umbrella. Under suitable conditions it will grow more than a metre high, and if that is too tall for your particular purpose, then try the smaller growing Cyperus vegetus. This has broader foliage than Cyperus longus, borne in typical fashion, and during late summer is surmounted by tufted spikelets of reddish-mahogany flowers.
Finally, no review of sedges, reeds or rushes would be complete without mentioning Sparganium ramosum (bur reed). Not because it is something special, although it does have a peculiar charm of its own, but because it is not infrequently sold to the unsuspecting pool owner. Unfortunately, sparganium looks really strong and attractive in its formative life and this is very tempting to the nursery owner. It also develops quite pleasing foliage and produces strange, bur-like, seed heads. However, it is neither of these that present problems, but the invasive rootstock which sends shoots up in all directions. This spreads out an armoury of rhizomes, each with a very sharp growing point which will quickly puncture a pool liner.