Plant profiles > Parsonsia

Family : Apocynaceae

This genus of climbing plants extends from tropical Asia to New Zealand, and is most heavily represented within Australia and New Guinea. Of its c. 40 species, the 3 New Zealand species are endemic (found nowhere else in the world). Parsonsia climbs by means of twining its stems around the branches of trees and shrubs, or any other suitable support. This stands in contrast to the manner by which climbing genera such as Clematis and Passiflora climb, through fastening specialised tendrils to their supports.

They are collectively commonly known as New Zealand jasmine - a poor comparison, considering the excessively weedy nature of the introduced jasmine, Jasminum polyanthum (and the fact that Parsonsia spp. are from a completely different family to jasmine). When people ask why botanists or horticulturists usually refer to plants by their botanical names, it is often related to the confusion or false relationships that a common name can infer (as in the case of Parsonsia).

In contrast to J. polyanthum, the two commonly available species of Parsonsia make excellent garden plants. Parsonsia heterophylla and P. capsularis both bear scented flowers (hence the common name of 'jasmine') that are normally white or cream, but vary into shades of yellow, or even red or pink in the case of P. capsularis.

They are well suited to growing through small trees or very large shrubs (imitating the association between such plants in nature), or growing on artificial supports, such as wire or over pergolas. When mature, the evergreen foliage of both species is an added attraction to the flowers. According to Thomas Cheeseman, both of New Zealand's main species of Parsonsia, P. capsularis and P. heterophylla, were observed by Joseph Banks and Daniel Solander on Captain Cook's first voyage to New Zealand, in 17691.

Parsonsia heterophylla
Kaihua; New Zealand jasmine; Akakiore

This is the larger of the two common species of Parsonsia, and is also distinguished by small differences in the flower (which is generally larger than the flower of P. capsularis). Its specific name ('heterophylla'), refers to one of the most unusual features of this plant - the wide variety of leaf forms exhibited by this species in its juvenile stages2. Leaves on young plants range from short, club-like forms to long, sword shapes with wavy edges - with a plethora of differing forms and colours occurring on a single plant. They often bear an unusual dark brown colouration, similar to juvenile leaves of the toothed lancewood, Pseudopanax ferox.

When, after a few years, they have made the transition to an adult state, the leaves become comparatively uniform (and conventional) in shape and colour. Plants are sometimes propagated from adult foliage, to avoid the juvenile phase and provide plants that will flower from the first year. However, the unusual appearance of the plant in its juvenile form represents an interesting adaptation, and has its own aesthetic qualities.

Flowering commences as the plant changes towards its adult state. Mature plants often bear their heads of scented blossoms in great profusion over summer, lending a different appearance to the trees or large shrubs through which they climb. As stated previously, the flower colour is normally white or cream, but yellow forms also occur within P. heterophylla. As with many native species, the flowers are attractive to nocturnal moths - who presumably play some role in their pollination.

P. heterophylla has a very wide distribution in New Zealand, occurring from the Three Kings Islands in the Far North to Stewart Island, and growing from the coast up to lower montane forest. It is most commonly found in somewhat open habitats, such as bush margins and coastal forest; although it can tolerate considerable amounts of shade.

Whilst it can grow to 10m within nature, it attains smaller dimensions within gardens, and can be kept very compact through appropriate pruning (due to the inclination of the plant to maintain fairly dense foliage).

I have seen Parsonsia heterophylla growing in a wide range of situations, perhaps the most unusual of which was a pair of plants that ascended two 8m Chinese Windmill Palms (Trachycarpus fortunei), in minimal soil at the gates of an industrial yard in central Auckland. It is worth noting here that viewing plants performing well under such challenging conditions is often a good indicator of the gardenworthiness of a species.

Parsonsia capsularis var. grandiflora
Kaiwhiria; Akakiore

Contrary to the impression provided by its botanical name ('grandiflora' means 'large flowers'), the most distinctive characteristic of this variety of P. capsularis (which is, roughly speaking, found from Auckland north) is the large size of its leaves3. The leaves are so markedly different from other varieties of Parsonsia (being often considerably rounder), that upon viewing this plant for the first time, I initially mistook it for a Convolvulus of some kind.

Given some of the habitats in which it naturally occurs, this looks to be a very good and resilient native climber for gardens. On the west coast of Auckland, it grows within open, exposed coastal forest, in close proximity to the beach; where I have seen it scrambling over rocky outcrops and climbing through the West Coast kowhai, Sophora fulvida. The foliage is a bright green, and can assume a variety of shapes; from rounded, oval leaves, to more pointed, narrow forms. Its flowers are usually cream in colour, but can vary into shades of orange, red, white or pink.

Although not acutely threatened, Parsonsia capsularis var. grandiflora is officially listed as 'Naturally Uncommon'. With its attractive, bold foliage and scented flowers, this northern native should increasingly receive the attentions of gardeners and landscapers from Northland and Auckland. Lawrie Metcalf (one of New Zealand's foremost authorities on the cultivation of native plants) alluded to this in 20004, when writing that although no forms of P. capsularis var. grandiflora were yet in cultivation, it would "in all probability ... yield one or two good garden plants." Subsequently, Oratia Native Plant Nursery have introduced this fine plant into the trade.

Parsonsia capsularis var. grandiflora was recognised as being distinct, almost 100 years ago (around 1916), by the botanist, Harry Carse.

 


Footnotes

  1. Cheeseman based this assumption upon observations of Solander's descriptions and drawings, in which Solander considered the two species to be separate varieties of the same species (as discussed in Cheeseman's "Illustrations of the New Zealand Flora', 1914; Pl. 135).
  2. This characteristic, by which plants have juvenile foliage that is very distinct from adult foliage, is called heteroblasty. It is also evident (to a lesser extent) in P. capsularis.
  3. As described by Peter De Lange, within 'Supplement to Eagle's Complete Trees and Shrubs of New Zealand : Additional Notes' (Eagle, A. 2006. Dunedin : Botanical Society of Otago).
  4. Within 'New Zealand Trees and Shrubs : a comprehensive guide to cultivation and identification'. 2000. Auckland, Reed Books (p. 319, under the description for P. capsularis var. rosea).