Cabbage trees are endemic to New Zealand, and they are well recognized very distinctive trees. Get up close and feel their trunks – there are many to choose from around Grovetown lagoon. They have a rough trunk, which when you press it, feels a bit spongy and cork-like. When the tree is young it has a single trunk. Branches grow from the flowering panicles, so each time it flowers, more branches appear. Older cabbage trees sometimes grow new branches directly from their trunk and this allows them to regenerate after storm or fire damage.
The nectar of the flowers is very sought after by bellbirds, and tui. The fruit is enjoyed by bellbirds, tui and kereru, and the leaves and the rough bark provide excellent homes for insects such as cabbage tree caterpillars and moths, small beetles, fly larvae, wetas, snails and slugs. Many of these insects provide food for native birds (such as saddleback and robin, where these birds still survive).
The rough bark also provides opportunities for epiphytes to cling and grow, and lizards hide amongst the dead leaves, coming out to drink the nectar and to eat the insects too.
Much of the cabbage tree was useful to pre-European Maori. Because they are high in natural sugars, cabbage trees were used to sweeten other foods. The leaves could be used for weaving and for making plaited ropes. The fibre made from cabbage tree leaves is stronger than that made from harakeke (flax). The fleshy root, the core of the trunk and the young leaf bud all provided food for Maori and later, for early European sailors. Various parts of the tree were also used to treat injuries and illnesses, either boiled up into a drink or pounded into a paste.
Despite the invasions of introduced plant and animal pests, the lagoon is still providing habitat for rare plants. The rare swamp nettle (Urtica perconfusa) is one threatened species existing in a small area at the lagoon. And just so you will remember the latin name next time you see it: Urtica comes from the Latin verb ‘urere’ which means ‘to burn’.
Swamp nettle is also known as creeping nettle, and is a New Zealand native that is declining in numbers. With stems that can reach up to 2m tall, and narrow leaves 3-8cm long, the branchlets, leaf stalks and leaves are sparsely clad in stinging hairs. It is a sparingly branched herb but these hairs can inflict a painful sting if your skin comes into contact with them.
The flowers of the swamp nettle are inconspicuous, with a green to reddish colour, and can be found throughout the year as this nettle flowers through all seasons.
However, it does make an important contribution to the wetland habitat as it is a host plant for the endemic red and yellow admiral butterfly (the caterpillars eat the nettle).
It is generally found on lake margins and fertile to semi-fertile wetlands. It is often hard to see in wetlands as it frequently grows at the base of Carex secta trunks, or threaded through Phormium tenax (flax). Being an adaptable species it is often found with willow species, sometimes as a low epiphyte on willow trunks. In all these habitats the swamp nettle is at risk from wetland clearance, drainage and also the spread of smothering weeds such as wandering jew (Tradescantia fluminensis).
New Zealand’s tallest forest tree, the kahikatea (Dacrycarpus dacrydioides), once dominated the forests that covered much of New Zealand’s swampy lowland areas. The kahikatea groups closely with other kahikatea, intertwining its buttressed roots with its neighbours for support in unstable swampy ground. (It is perhaps for this reason that the kahikatea has evolved with such a tall, straight trunk with no lower branches, to enable it to “huddle” with others for stability.) In autumn, throughout the lowlands of New Zealand, numerous forest birds chattered noisily in its canopy, feeding on its abundant red berries. These berries, called koroi, were also a valued food source for Maori, who climbed up the smooth branchless trunks to harvest them.
Captain Cook and his companions had great hopes for this 60 metre high giant when they first encountered it and named it “white pine”, reflecting their confidence in its suitability as timber.
The kahikatea is an ancient survivor from the Jurassic period, evidenced by geologists’ discoveries of its pollen and leaves in Jurassic rocks, some 160 -180 million years old. This was a time when neither birds nor flowering plants had evolved; rather than kereru/wood-pigeon, kaka and tui, the kahikatea’s prolific fruits were probably feasted on by pterosaurs (or flying dinosaurs, commonly known as pterodactyls).
It has a pivotal ecological role in the swamp forests of lowland New Zealand, but the stopbanking of rivers and the draining and conversion of swamps means that stands of kahikatea are becoming rare. We hope to eventually re-establish stands of Kahikatea in areas of Grovetown Lagoon.
Raupo can be seen in different areas around the lagoon - look for the distinctive large furry brown cylindrical seed head. It’s known to many of us as the “bulrush”. Raupo grows in standing water to about 3 metres tall, often forming large dense masses in swamps, lake edges and damp seepages on hillsides. They grow from Northland to Southland, from coastal swamps up to 1000 metres above sea level.
Like many water plants raupo spread by way of their swollen roots or rhizomes, known to the Maori as akakoareare. The plants have light grey- green strap-like leaves which die back in the winter to resprout again in the spring.
The head of the raupo has two parts. The upper skinny part carries male flowers, the lower velvety brown part, the female flowers which eventually produce tiny seeds.
Virtually every part of raupo is useful. Maori used its dried leaves for thatching or floor covering, for making sails, fishing rafts and floats, for thatching whare and canoes, for weaving baskets, cloaks and kites. Raupo was also an important food item for Maori.
Large parties collected raupo pollen (pua), mixed it into a porridge or gruel like sweetcorn and baked it into cakes. Sometimes these were flavoured with crushed manuka beetles. The roots of the raupo plant were peeled like bananas and eaten steamed.
Flax is an iconic native plant in New Zealand which is thriving at Grovetown Lagoon. It is becoming a favourite garden plant and also a subject used by many artists. There are two identified species of flax in New Zealand. Common flax (Phormium tenax) is found throughout the country, especially in wet areas, while mountain flax (Phormium cookianum – also called wharariki) is found both at higher altitudes and along exposed coastlines.
Flax grows up to 3 metres high with flower stalks that can reach up to 4 metres. It has seed pods that stand upright from the stems. Mountain flax never grows as large as common flax, rarely reaching more than 1.6 metres high, and its seedpods hang down. Within the two flax species, there are numerous different varieties of flax. Some have drooping, floppy leaves while others grow as stiff and upright as spears. Flax flowers can vary in colour from yellow to red to orange. Flax was a valuable resource to Europeans during the 19th century because of its strength. It was New Zealand’s biggest export. Flax bushes will often support a large community of animals, providing shelter and an abundant food source. Tui, bellbirds/korimako, saddlebacks/tïeke, short tailed bats/pekapeka, geckos and several types of insects enjoy nectar from the flax flower.