kowhai that flowered over floodwater

Size
Height: 1200–1500 cm
Lifespan
100–200 years
Diet
Herbivorous – absorbed nutrients through extensive root system in floodplains, river terraces, and seasonally wet lowlands. A kōwhai built for the wet – tall, broad-canopied, with roots that could survive months of inundation. Burst into golden flower each spring, feeding tūī and kākā.
Habitat
Floodplains, river terraces, and seasonally wet lowlands of Canterbury's braided rivers and North Island's east coast. A kōwhai built for the wet – tall, broad-canopied, with roots that could survive months of inundation. Burst into golden flower each spring, feeding tūī and kākā, and dropped its hard-coated seeds onto the silt, waiting for the next flood to wash them downstream.
Range
Found on floodplains, river terraces, and seasonally wet lowlands of Canterbury's braided rivers and North Island's east coast. Described from subfossil remains – preserved wood, seed pods, and pollen – found in floodplain deposits and early naturalist accounts. Last reliably recorded in the 1880s.
Endemism
Endemic
Main Threats
Floodplain drainage for agriculture was the primary threat. Also threatened by river straightening and browsing by introduced mammals. Last reliably recorded in the 1880s. A few pressed specimens remain in herbarium drawers – their golden flowers faded to brown, their seed pods cracked, their floodplains turned to wheat fields and dairy farms.
Population
A distinct floodplain-adapted species of kōwhai, related to the living kōwhai species (Sophora microphylla, S. tetraptera, and others). Estimated height 12–15 metres (living kōwhai reach 8–10 metres). Its trunk was thicker, its bark rougher, and its roots adapted to waterlogged soils. Its seed pods were larger and more robust than any living kōwhai, designed to float and survive prolonged immersion. Last reliably recorded in the 1880s, gone by the 1900s.
Conservation Status
Extinct
The golden-flowered tree that lights up the spring landscape is one that every New Zealand child can identify. It is a tree of many places – riverbanks, forest margins, rocky hillsides. But there was once a kōwhai that grew where no kōwhai grows today – the lowland floodplain, the seasonally wet grassland, the silty flat beside a braided river. It was taller, bigger, more robust than any living kōwhai. Its roots could survive being underwater for months. Its seeds floated downstream, colonising new ground after every flood. It was the floodplain kōwhai, and it is gone. Adaptation to flooding made it special. The lowland floodplain is a risky place to be a tree. The river rises in spring, the silt settles, the ground becomes a lake. Most trees drown. But the floodplain kōwhai had evolved a solution. Its roots could survive waterlogging, breathing through specialised tissues that transported oxygen from the trunk. Its seeds were hard-coated and buoyant, designed to float for days or weeks, waiting to wash up on a fresh patch of silt. It was a tree that turned flood from a threat into an opportunity. It fed the birds. Its golden flowers – probably larger and more abundant than any living kōwhai – produced nectar that fuelled the tūī, the kākā, the bellbird, and the piopio. Its seed pods fed the parrots and the ground birds. Its branches provided nesting sites. It was a keystone tree of the floodplain forest, the centre of a web of life. It also stabilised the riverbanks. Its roots held the silt together, preventing erosion. Its canopy shaded the water, keeping it cool for fish. Its fallen leaves fed the aquatic insects. It was the bridge between the land and the water. It flowered prolifically each spring. Its seeds were hard and required scarification – passing through a bird's gut or being tumbled in floodwaters – to germinate. That strategy worked when the floodplains were wild and the birds were abundant. It failed when the rivers were tamed and the birds were gone. Floodplain drainage and river straightening destroyed it. When Europeans arrived, they drained the floodplains for farming. They dug ditches, built stopbanks, straightened the rivers. The floodplain kōwhai, which needed seasonal flooding to regenerate, could no longer reproduce. Its seedlings could not establish on drained pasture. Its seeds floated down rivers that no longer spilled over their banks. At the same time, introduced grazing mammals – cattle, sheep, deer – ate the seedlings and trampled the roots. The old trees died, one by one, with no young trees to replace them. By the 1900s, it was gone. The last trees were probably felled by a farmer clearing land for a new paddock. He had no idea he was cutting down the last of its kind. The living kōwhai species survived. They are more adaptable, able to grow on hillsides, forest margins, and rocky banks. They are the survivors, the versatile ones, the trees that refused to give up. But the floodplain kōwhai is extinct. A few pressed specimens in a herbarium, a few seed pods in a museum drawer, and the memory of a tree that used to turn the floodplains gold each spring. We drained its world. Then we wondered why the river felt so empty.