Aotearoa New Zealand has a plethora of weird and wonderful plants. The ferociously spiky speargrasses are some of our most distinctive plants and an iconic feature of New Zealand’s high-country, especially when flowering. Te Papa Research Scientist Lara Shepherd and Botany Curator Leon Perrie recently embarked on a new project with Manaaki Whenua’s David Glenny to re-assess the number of species of speargrass. Here they give an overview of the genus.
Speargrass (Aciphylla) is a genus of flowering plants in the carrot family. At first glance, speargrasses appear very different from carrots. But they both have taproots, and the speargrass species also have their small flowers grouped in clusters called umbels, a feature of the carrot family.
There are around 40 species of speargrasses, with an additional 9 forms with tag-names that may also be distinct species. New Zealand is the centre of diversity for speargrasses with all but two of the species only occurring here (the other two are restricted to Australia).
Speargrasses in New Zealand occur from coastal to alpine regions and have a huge diversity of forms, especially in the South Island. They range from tiny, soft-leaved, difficult-to-find herbs, to large spiky mounds a few metres across with huge, pointed clusters of flowers.
Twenty-two of the New Zealand speargrass species are considered of conservation concern. Threats include land clearance and browsing by introduced animals. Hares browse the leaves (they manage to circumvent the spiky defences by nibbling the sides of the leaves) and pigs will uproot entire plants in order to eat the tap root.
The Ngāi Tahu name for the larger speargrass species is taramea and their sap is prized as a fragrance. The smaller species are known as papaī and their taproots were eaten. Some of the species in each of these groups are featured below.
Large-leaved species, taramea
Large-leaved speargrass species are often highly prominent in the landscape, with huge triangular clusters of flowers up to several metres tall.
Most of the large-leaved species are heavily defended with sharply pointed, rigid leaves and flower bracts, features proposed as a defence against moa browsing. Two species only occur on the Chatham Islands, where there were no moa, and these have soft leaves.
The large species exhibit mast flowering meaning that they flower en masse every few years (like beech trees). This feature is thought to relate to the availability of resources – plants only flower when the weather has been favourable and sufficient energy stored to produce the costly large flower spikes.
Speargrasses are dioecious, meaning that there are separate male and female plants. Since flowering is less costly for male plants (because they don’t have to subsequently form seeds), they seem to flower more frequently than female plants, at least in the large species.
Small-leaved species, papaī
The smaller species of speargrass have a variety of forms. Some species form dense cushions with rigid leaves. These occur high up in the alpine zone.
Others form looser, less-dense clumps.
There are several speargrass species with narrow, sparse leaves. They can be difficult to spot as their leaves blend in with the surrounding tussock leaves. However, they become much easier to see once flowering.
Some species have softer leaves vaguely resembling those of carrots.
Other species look like smaller versions of some of the larger species.
Aciphylla hookeri and A. pinnatifida are two species that look quite unlike the other speargrass species. The leaves of Aciphylla hookeri resemble those of thistles.
We recently spent six weeks in Te Waipounamu South Island collecting speargrasses for our research. Keep an eye out for future blog posts about our trip, how we avoided injury whilst collecting and some of the critters that rely on speargrasses.