December in the forest with Chris Horne and Barbara Mitcalfe
Griselinia lucida, Puka, Broadleaf
Ten TTC trampers joined us for our annual November Native Plant Recognition trip. After climbing through Birdwood Reserve's second growth regenerating native forest, we continued around the Sanctuary's perimeter track, climbed Wright Hill and descended through Burrows Avenue Reserve to Karori Main Road - a green urban traverse at a sedate pace, because of so much botanical interest.
In Birdwood Reserve we admired an enormous Griselinia lucida, puka ,(but beware- this name is also given to another plant). This sprawling giant had morphed through several different stages in its 100-year life. Commonly called broadleaf, it usually starts life as an epiphyte, (as northern rātā often does), as a seed perched in the crotch of a large tree. We'll call that, Stage 1.
If it gets enough moisture and leaf litter there to survive, over the years it sends pale fawn, deeply-grooved roots down the outside of the host tree trunk, searching for nutrients and moisture from the soil. Meanwhile, up top, the broadleaf crown is also developing its very distinctive shiny, large-leaved foliage. You will have noticed broadleaf leaves that have fallen to the ground, about 15 cm. x 10cm, with sides of unequal length, so that they join the stalk at two different points. This Stage 2 of the broadleaf's life lasts for many years, during which the roots proliferate down and around the host's trunk, becoming so heavy that they top- ple the old host tree and the whole “ensemble” becomes horizontal, with the ancient host tree, now dead, inside.
The broadleaf trunks then gradually re-orientate themselves to grow vertically, often reaching to c. 8m. This is Stage 3.
We stress that broadleaf, like rātā, is never a parasite, just an epiphyte, using another tree as a crutch. Our TTC group saw two huge examples of Stage 3 of this natural phenomenon, one in Birdwood Reserve, and one in Burrows Avenue Reserve. Look for those pale, thick, deeply-grooved roots descending from the crown of a host tree, and the unusually large, shiny leaves. Broadleaf's erect clusters of tiny green flowers are followed by tiny purple fruit.