Native Geranium Discovery?

Native Geranium Discovery?

To the untrained eyes of passers-by, the apparently insignificant pale pink flowers blooming from cracks and crevices along Auckland’s Oakley Creek barely rated a second glance.

Now they are generating increasing excitement among botanists, who believe the Oakley Creek geranium may be a new, previously unidentified native species. The plant’s discovery and preservation highlights how truly great things happen when engineering and environmental science join forces on infrastructure projects.

Not long ago, Oakley Creek was a sad example of how environments have suffered in the interests of progress. Its organic meandering – along with its host of aquatic life - had fallen victim to the straight-line logic of engineers and excavators. It was simply an engineering hurdle to be overcome and pummelled into shape.

When the green light was given to begin construction on Auckland's massive Waterview Tunnel, the $1.4 billion budget included significant ecological protection and restoration work in areas adjacent to the motorway extension.

In 2012, the Tonkin + Taylor ecology team began working on the restoration of the Oakley Creek around Mt Roskill when a local botanist drew their attention to this small, hairy plant. 

The geranium aff.retrorsum Oakley Creek (or to give the plant its Māori name, Te Auaunga) was discovered in 2004 by botanist Rhys Gardner, as part of an extensive study of the Waterview Connection’s ecological foot print.

Rhys, who has G. Oakley Creek flourishing in his own Ward Terrace garden, thought it odd that the geranium was so restricted in its habit. “It’s not at all weedy. I have it growing near my Xeronema (Poor Knight’s Lily).”

Tonkin +Taylor ecologist Kat Longstaff says that although it’s possible the geranium found its way to New Zealand from Australia - or that it is a variant of this country’s few indigenous geraniums - the recent discovery displays one significant characteristic that makes it likely to be a new species.

“The leaf stem hairs lie flat, rather than upright,” says Kat, who for the past year has been heavily involved with the Oakley Creek replenishment project. “It has some characteristics of the Canterbury and Auckland forms.

“The genus is rare around New Zealand and to find one that is not quite like the others…that’s really interesting, quite exciting, even if it turns out to be an introduced one.

“If it’s a new native species that will be really cool.”

The geranium was found growing alongside the Hendon Park/Allan Wood Reserve stretch of Oakley Creek. As is typical of all geraniums native to New Zealand, their swollen roots are obvious adaptations to dry, gravelly, sandy or light-loamy soils.

“It seems to favour grassland open to the sun,” Kat, explains.

The plants that could be left undisturbed were fenced off. Seed was then collected and propagated at Auckland’s Oratia Native Nursery. Since then some 1,500 G. aff.retrorsum Oakley Creek seedlings have been planted along the creek, which has at last been freed of its linear constraints and allowed to reclaim its original winding contours.

That’s great news for biodiversity, says Kat: “It provides positive flow changes, improves sedimentation and oxygenation - and provides habitats for things like eels, insects and food sources.”

The creek is recovering quickly. Further downstream, where native plants now line its banks and microenvironments are quickly establishing themselves, the eels have returned and are clearly feeling right at home.

Kat - also a herpetologist (an expert in amphibians and reptiles) - has found the improved working relationships between environmental scientists, engineers, construction contractors and infrastructure designers immensely rewarding.

“Now they come to us and ask, ‘what’s there, what might be there and what can we do about it?’

“I quite often rescue lizards and show people; they get quite excited. There’s a lot of cool stuff in little places.”