If people are only able to name one type of fern, there is a good chance that fern will be the maidenhair. Due to its widespread international use as a pot plant, and its ability to grow in many human environments (it is often seen on buildings or walls), maidenhair ferns are quietly omnipresent within our lives. Familiarity can sometimes breed disdain or indifference; and as a result, it might be easy to discount the value of this genus within gardens.
However, the New Zealand species of Adiantum rank amongst the most useful and attractive of our ferns, as they are able to provide a wide range of colours and effects within plantings. The light green of the so-called true maidenhair (Adiantum aethiopicum) is one of the brightest hues within the plant world, whilst the bluish-green of the common maidenhair (Adiantum cunninghamii) creates an altogether cooler atmosphere, and the large, hovering fronds of the giant maidenhair (Adiantum formosum, pictured below) form a diaphanous field that conveys a sense of lightness.
Adiantum is a widespread genus of around 200 species, with seven species native to New Zealand (3 of which are found nowhere else in the world1). The name, Adiantum, is derived from Greek, and means “unwettable”, in reference to the capacity of the fronds to shed water.
There are many New Zealand plants that deserve to be much more widely grown than they currently are, particularly when one considers the species that are usually proffered in their place. One surprising omission in the armoury of horticulturists is the lack of creeping ferns that are utilised within gardens and landscape work. So often we see individual fern specimens jammed together to form a mass that looks more like a rugby crowd than a natural plant association – where a creeping carpet would provide a more elegant ‘field’.
Adiantum cunninghamii is a classic example of the kind of creeping fern that should be planted more often. As alluded to above, creeping species do ‘fields’ so much better than a group of crown-shaped species. Much in the way that meadow grasses are able to form a flowing, continuous mass, they succeed (in a visual sense) because they have an appropriate sense of proportion, as well as a suitable ratio of density and openness.
Amongst our native species, A. cunninghamii is particularly well-suited to cultivation; on account of the fact that its foliage tends to remain full, where others can become a little sparse. Its bluish-green colour is also very appealing, as is its vigorous, patch-forming growth habit. A. cunninghamii generally reaches 15 to 20cm in height, and can spread to cover an area of several square metres.
As indicated by the name, common maidenhair, this is our most widespread maidenhair – it grows in the lowlands of all parts of New Zealand, except the Sub-Antarctic Islands. It is more common in reasonably dense shade, and it is in this aspect that it should be used within gardens.