Pseudopanax

The combined appeal of distinctive foliage and a range of useful growth forms has made members of the genus, Pseudopanax, popular landscape plants in recent years. With the exception of a small number of aberrant species, the general leaf form of Pseudopanax spp. is somewhat hand-shaped, a characteristic that leads to the often applied common name of ‘five-finger’. This name is not entirely accurate, as the leaves of many ‘five-finger’ species can bear between 3 and 8 leaflets.

The four ‘aberrant’ species are collectively referred to as ‘lancewoods’. In contrast to other Pseudopanax spp., they don’t have compound leaves (leaves made up of several leaflets), but rather bear simple leaves. The most commonly-grown species of lancewood are Pseudopanax crassifolius (simply known as lancewood) and P. ferox (toothed lancewood). They are two of the most remarkable trees in the New Zealand flora, on account of the major differences between their juvenile and adult phases (a characteristic which is discussed at more length in the plant profile on P. ferox).

As mentioned above, Pseudopanax spp. assume a variety of growth forms that are very useful within gardens. Several develop into compact, bushy shrubs (up to 3m) that are useful for screening or for providing structure within plantings, whilst others become upright small trees that can provide a good sense of scale within areas in which the presence of most other trees would become an imposition. The capacity of several species of Pseudopanax to establish scale within confined spaces is a major feature of the work of London-based New Zealand designer James Fraser, who utilises them amidst the small yards and tall elevations of London’s terrace houses.

Three native species that were formerly included in Pseudopanax have now been assigned to Raukaua, a genus that is almost confined to New Zealand (one outlier species, R. laetevirens, occurs in Patagonia) – and which, interestingly, receives its name from the Māori term for one of its species. The family to which Pseudopanax belongs, Araliaceae, is commonly called the ivy family, after its most famous representative. Other well-known members of the family are ginseng (Panax spp.), an important Chinese herbal remedy, and Fatsia japonica, a very commonly cultivated (although somewhat dumpy) ornamental of temperate climates.

Of all the distinctive features of the New Zealand flora, the prevalence of a characteristic known as ‘heteroblasty’ is perhaps the strangest. Put simply, it means that a plant has juvenile foliage that is markedly different from its adult foliage. This phenomenon, which is most strongly illustrated in the growth form of our two widely-known species of lancewood (P. crassifolius and P. ferox), has attracted great interest from scientists and writers; as to the reasons behind its origins.

The most well-known of the theories that has been put forward is that such trees have evolved in response to browsing by the now-extinct moa; whilst the theory that is generally accepted as being more credible is related to climatic factors. However, who knows ? It may be that a combination of several influences causes a particular growth form within a given species.

Botanical pedantry aside, what is of more interest to us is the aesthetics of this unusual plant. I sometimes tire of plant descriptions that refer to a plant as ‘sculptural’¹; but in this case, the shoe fits very well. P. ferox grows for many years as a single leader of long, downward-facing, toothed leaves that are often a peculiar brown colour. The leaves have the appearance of a primitive stick insect, and are arranged in an orderly manner on the trunk (which develops a gnarled, corrugated surface over time).

Then, at a height in excess of 2m, it makes the gradual transition to its adult form; a comparatively conventional lollipop-shaped canopy of fairly plain, dark green leaves. Although it is the bizarre juvenile form that attracts most attention to this species, we consider the adult form to be the most valuable stage of its growth. It is extremely rare to find a tree with such perfect dimensions and proportions; a clean (and attractive) trunk that supports a compact head of dense foliage.

In his 1889 work, ‘The Forest Flora of New Zealand’, Thomas Kirk noted that the tough midribs of the leaves were used by settlers as bootlaces, and for mending bridles and other related gear. Just in case one needed further discouragement for destroying native trees such as this, Kirk also wrote that freshly felled timber gives off a strong, unpleasant smell. P. ferox was described as a species by Kirk, after it had been discovered by John Buchanan, who misidentified it as Pseudopanax crassifolius. It is a naturally uncommon species with a scattered distribution, ranging from Ahipara in the Far North to Southland.

Toothed lancewood is especially tolerant of dry, difficult conditions; growing as it does in habitats such as cliffs, rock outcrops and secondary dune forest. The combination of such adaptability and its extraordinary appearance makes this marvel of evolution one of the finest landscape plants that our flora can offer; one which is increasingly being appreciated as people open themselves up to the wonderful array of plants that populate our natural landscapes.

The cliffs at mainland New Zealand’s northernmost point are formed from an unusual underlying geology, referred to as ultramafic rock. The soils that form over ultramafic rock are characteristically low in nutrients, and high in minerals that are toxic to plants. As a result, these environments generate unique communities of plants that are adapted to difficult conditions – often taking on significantly different forms to those that they normally assume elsewhere (in some cases, to the extent of constituting distinct species).

The most striking example of this is the creeping character that many otherwise upright species manifest at the Surville Cliffs. Although not as pronounced in this species as it is in other Surville Cliffs endemics, such as the creeping North Cape forms of Corokia cotoneaster and Phyllocladus trichomanioides, a stunted growth form is one of the two main distinguishing features of this variety of the common coastal small tree, houpara. The other characteristic feature of the North Cape form (which is perhaps even more horticulturally significant than its compact habit) is the dark purplish-black colour of the new foliage.

Colouration of this kind does occur elsewhere within Pseudopanax; as the well-known species Pseudopanax discolor bears dark maroon foliage, and both the commonly-grown lancewood species (P. crassifolius and P. ferox) exhibit a range of unusual leaf colours. However, the North Cape houpara has a stronger, sharper hue than the somewhat muddy colour of P. discolor, and bears a significantly different growth habit to the lancewoods.

As may be gathered from the details of its natural habitat (wind-blasted, toxic cliffs), P. lessonii (ii) is a tough species for planting in northern parts of New Zealand. It will reach in excess of 2m, but tends to remain close to 2m tall – sending new branches from the base to form a dense clumping shrub, in contrast with the taller, upright form of typical P. lessonii. This makes it an extremely useful shrub for urban plantings, where a naturally compact form is a great advantage. It is also graced with very attractive foliage, that acts as a good background to other species.

Similar forms, which a comparable growth habit and other characteristics (particularly regarding leaf morphology) also occur at other points on Northland’s northeastern coastline – such as at Butler Point and Henderson Bay. The plants pictured above are growing in a very interesting area of coastal scrub on an elevated stretch of coastline at Henderson Bay, in association with Kunzea linearis and a distinctive form of Coprosma that we use periodically in our work as a sprawling, small-leaved groundcover.