The Humble Domatia
One of the most common groups of native plants in New Zealand are Coprosmas. There are around 60 native species of Coprosma in New Zealand. They are quite a varied bunch with leaf sizes varying between under 2cm to over 20cm long. Coprosmas are related to Coffee and have small berries that are edible in all species. A favourite is the beautiful marble like blueberries of the Sand Coprosma (Coprosma acerosa).
Like all plants, Coprosmas have their challenges in keeping unwanted organisms from slowing their growth. For the Coprosma one of their greatest challenges is the presence of fungus that can cover the leaves and prevent light reaching the photosynthesising elements of the plant. Luckily, there are various mites in New Zealand that love to munch on the fungus on leaf surfaces, but how do plants encourage such mites to come and hang out on their leaves? They build them a home of course! Scientists call these homes Domatia which comes from the latin “domus” meaning house. These are little hollows created where the small veins of the leaf join the main “midrib” vein running down the middle of the leaf. The plant creates these little hollows to provide protection for the mites so that they are encouraged to call that particular coprosma leaf home and busily munch away on the fungus keeping that leaf nice and clear for photosynthesis.
These incredible behaviours are so easily missed. Who goes looking for tiny holes in leaves?
The Hot Horopito
One of the main threats to plants is of course browsing by herbivorous animals, and many plants have found a number of ways to protect themselves from this. Some have evolved with spikes, others have small leaves spread out on tough stems but one of the most interesting is the approach taken by the Horopito (Pseudowintera Colorata). This plant is often called the pepper tree for good reason, when bitten into, the leaf delivers a peppery hot taste to the mouth that builds to quite a fiery experience. No Herbivore is going to be able to stand munching on vast quantities of those leaves! The Maori used this leaf as a flavouring but also found that the crushed leaves helped with a number of fungal infections including ringworm of the skin and oral fungal infections. In fact even today you can purchase a variety of products that contain Horopito to help treat fungal infections.
These are some of the many fascinating plant stories that our guides love to share and allow our guests to enjoy our beautiful surroundings with new eyes. Join us on one of our trips and see what else you can learn.
Shining Karamu- (Coprosma Lucida)
Horopito- Pepper Tree, (Pseudowintera Colorata)