Misty Mountain Hop

January 16, 2019

As we entered into what must be one of the largest remaining populations of Carmichaelia stevensonii, at the headwaters of George Stream in the Seaward Kaikouras, we got the distinct sense of Winston breathing a big sigh of relief. Having hunted in this area several years beforehand (for animals, not plants), Winston was our guide to finding New Zealand’s most impressive tree broom – for the first time in the wild for all of us bar our esteemed leader.

By Winston’s own admission, after several hours of walking/clambering (and a number of forks in the stream), it was clearly good to shed the pressure of having to retrace one’s steps through a mountain range with sufficient accuracy – a feeling that I know well from many trips where I have had to perform the same role for friends and colleagues (and, in one instance, for a BBC film crew).

In the days before this walk (which was the most keenly anticipated part of a four day field trip/nerdfest to Marlborough for the core O2 staff), the forecast had furnished me with visions of clear skies beneath which I would be able to photograph Carmichaelia stevensonii in nature’s fully illuminated glory. However, the thick cloud that often settles upon the Seaward Kaikouras in summer provided an entirely different, yet equally welcome, atmosphere for us to experience this environment.

Although present at lower altitudes, Carmichaelia stevensonii is frequently associated with subalpine scrub in this geologically active part of the country – notably in places where disturbance, such as that caused by rockfalls or the violently fluctuating levels of streams, maintains the open conditions that many members of the pea family specialise in.

Interestingly, as a setting for photography, fog presents wildly varying conditions – as demonstrated by the image below, right, in which a view downhill (through the fog) amplifies the colour on the weeping broom and surrounding vegetation (in stark contrast with the almost monochromatic face presented when looking up through – or across – the same specimens).

Although the main event was Carmichaelia stevensonii, there were many other interesting plants along the way. Foremost amongst these for me was Olearia coriacea (pictured above, left), which is a compact species of shrubby daisy endemic to south Malborough and northern Canterbury. Having planted this elegant species before within South Island projects, I was hopeful of viewing it for the first time in the wild. Fortunately for me, it is a common constituent of the scrub and woodland edge communities around and leading up to the headwaters.

As the moisture borne by the enveloping clouds dripped off the tips of C. stevensonii‘s weeping branches, the reason for its distinctive form seemed somewhat self-explanatory – especially when compared with similar species of tree broom from Marlborough.

Some mountain goat antics (instigated by Rob) got us up into the kind of steep colluvium that constitutes one of the major habitats for C. stevensonii (as pictured below). This kind of semi-stable rockfall (which had a significant proportion of a beautiful red stone that I guessed might be argillite) is effectively the toe of the much steeper mountain sides above the stream valleys. It is therefore prone to further deposition of loose stone around the base of trees as these mountains creak and groan (one can see a buildup of rock around one trunk below), and also characterised by considerable depths in which the profile consists of high proportions of rock, as opposed to a more conventional soil profile.

Like many places worth visiting throughout the country this rugged walk (which is primarily known as a hunting block, leading up to the substantial conservation area), there are a couple of points that are not for the faint-hearted. This is ably demonstrated by our friend, Tim Le Gros (of Titoki Nursery), who (like the rest of us) had an acute interest in clinging to the bank shown below, rather than slipping down into the cascade that beckoned beneath his slightly tenuous foothold.

That said, George Stream was presenting a comparatively gentle face upon our visit, based on the evidence writ large upon manuka tree trunks towards the margins of lower parts of the riverbed. The sheer force of gravel borne by rushing waters (when in flood) practically ringbarked these trees, and offers a clear reminder of why one should not venture into certain drainage systems during significant rainfall events (when flash flood events generate this level of power within minutes).

As noted previously, this was no one-trick expedition, as many noteworthy plants occur within this area. One of the greatest surprises that we encountered in lower reaches of the river (I should add here that, despite its title of George Stream, river is a more apt term for envisaging the water volume that passes through here) was the largest population of Pseudopanax ferox that I have ever seen.

I had seen records for the species here, but one never knows quite what that means. Sometimes, records can be for species that have since disappeared; at other times, they note isolated specimens; and in others, they can point towards significant populations such as this – where toothed lancewood (shown below growing in woodland with large numbers of matai and many small-leaved shrubs/trees) grows in a wide range of ages, and on both sides of the river (including on its regularly disturbed margins).