New Zealand Plants and their Story
The Salt Meadows and Salt Marshes
The Salt Meadows and Salt Marshes.
Along the banks of tidal rivers and estuaries there is frequently low ground covered at flood tide with brackish water, or, where higher, subject merely to a periodical submerging. Of both such situations the covering is fairly uniform throughout New Zealand. Colonies of rush-like plants form the bulk of the vegetation. The most striking is the rush-like Leptocarpus simplex, whose stiff, reddish, jointed stems, a yard or more tall, render it very conspicuous. It belongs to a family (Restionaceae) confined almost entirely to South Africa and Australia. A true rush (Juncus maritimus, var. australiensis) is also very common, but it has not been found south of Timaru. Dotted over the salt meadow, or growing in close masses, is the shrubby ribbonwood (Plagianthus divaricalus), a shrub of a dense habit, and made up of slender, wiry, dark-coloured interlacing twigs covered page 81with narrow leaves, most of which it casts off in the autumn. Its relationship to the beautiful lacebarks and ribbonwoods is indeed concealed in its habit, but revealed in the structure of its minute flowers and fruit, as well as in its tough bark.
On the drier ground of the salt meadow are a number of creeping, turf-making plants, mostly with long roots and small thick leaves. The chief of these are Samolus repens, a white-flowered plant of the primrose family, but not a bit like a primrose; Selliera radicans, which has a curious corolla, looking as if a portion had been removed, also white; Cotula dioica, with aromatic leaves and yellowish button-like flower-heads; and Atropis stricta, a small grass. In some places, but by no means everywhere, growing in the pools or streams, is a beautiful musk (Mimulus repens). Its flowers are bright lilac in colour, with an orange throat. Extremely abundant also in some localities (e.g., on the northern shores of Cook Strait), and dotting the ground everywhere, is the pretty relative of the last-mentioned, Mazus pumilio. The curious Eryngium vesiculosum, a plant of the carrot family, which can increase enormously by means of runners, and so become a weed, is an occasional salt-meadow plant.
Where the water cannot get away, and the ground is never dry, and uncovered only at low tide, will be found a salt marsh. In the wettest places colonies of the great bulrush (Scirpus lacustris) will be present, but only where the water is not too salt. More salt-enduring is the smaller Scirpus maritimus. Leptocarpus simplex will generally be the dominant plant, and will cover many acres to the exclusion of all else. A sedge, Car ex litorosa, is peculiar to the salt marsh. Many of the plants mentioned above also occur, specially Juncus maritimus. These salt-marsh plants are of considerable economic importance, as they help to build up solid ground in estuaries, and also to maintain the banks of tidal rivers.