Selliera

At the margin of sea and land, there is often a zone in which plant growth is only possible for a small number of specialists. Due to the editing effect of salt water, habitats in these zones can have quite a simple, uniform appearance – as in the case of salt meadows (the turf communities that frequently occur near the high tide mark).

Selliera is one of the most conspicuous elements of this type of vegetation, as it is widely distributed and highly visible (on account of its bright green foliage). Its role in clothing the edge of the land is surely the reason for its most common name in Te Reo Māori, remuremu. The word, ‘remu’ translates as edge or hem.

Inspired by its natural inclination to form a uniform turf, horticulturists have (in recent years) increasingly utilised our species of Selliera for groundcover, and even as an alternative lawn. Its vibrant, light green colour makes an expanse of Selliera a beautiful sight; one which is further enhanced by the appearance of its copiously-produced white flowers in summer.

The scent that these flowers emit attracts various insects that are persuaded to assist in the plant’s pollination by a small supply of nectar within the flower. The eminent botanist, Thomas Cheeseman, described this process in detail, and surmised that flies are the most important agents of pollination (although a range of insects visit the flowers)¹.

New Zealand has three currently recognised species of Selliera, although one of these (S. microphylla, a plant of montane habitats in the Central North Island) is considered to be potentially doubtful². Selliera radicans is the most widespread species, whilst S. rotundifolia (pictured below, in fruit) is confined to the western coast of the lower half of the North Island.

The genus consists of a very small number of species³, and is found in New Zealand, Australia and Chile. Its name commemorates a French botanical artist (Francois Noël Sellier) of the 18th Century⁴.

When people talk of Selliera as a garden plant, it is almost invariably S. radicans to which they refer. This is an excellent groundcover for open conditions where it is permitted to receive enough moisture. It has become increasingly popular in recent years, due to the masses of white flowers with which it covers itself and the cheerful hue of its foliage (which brightens up any area that it inhabits).

S. radicans is a slightly variable species, with forms from distinct areas exhibiting differences in leaf shape and size; and some selection has been undertaken for horticultural purposes. An important point in growing Selliera radicans well is a rule that applies to many creeping herbaceous groundcovers. This growth form is commonly associated with damp sites in nature, and when they are subjected to extended dry periods within gardens, they can become patchy and die back.

Geoff Davidson of Oratia Native Plant Nursery has also identified another tip regarding S. radicans‘ cultivation. By observing its conditions within nature, Geoff noted that a major factor in the formation of pure swards of Selliera radicans is the excluding influence of salt. Therefore, he suggests controlling weeds (in lawns of Selliera) via the periodic application of salt water. When carrying this out, one should consider the issue of run-off into neighbouring garden areas – and this should play a role in the positioning of any Selliera lawn.

One characteristic that is shared by many salt-tolerant plants is the retention of water within the leaves, a feature that gives leaves a fleshy or succulent appearance. Selliera radicans is no exception; for although its leaves do not appear inordinately swollen, they contain a considerable water content.

Whilst I have primarily written (earlier in this profile) about Selliera radicans‘ role in coastal salt meadow vegetation, it does occur in other habitats – including sand dune depressions, inland lake and stream margins (including in the cold interior of the North and South Islands), and even coastal cliffs. In the latter situation, it tends to grow within seepages in cliffs, thereby receiving the moisture on which it relies.

S. radicans is found on both our main islands, Stewart Island and the Chatham Islands; as well as occurring naturally in Australia and Chile. In the image shown above, it is growing in damp coastal turfs at mainland New Zealand’s southernmost point, Slope Point, where it occurs in thick association with other coastal turf species, like Leptinella dioica.