Even though I have a degree in Biology, I’ve never really had any interest in plants or botany. Oh, don’t get me wrong, I like the pine, spruce and aspen forests in Colorado as much as anyone else, and I grew up with the deciduous forests back east in the United States. I’ve even been known to grow a tomato plant now and again. But I’ve been completely blown away by the native forests here in New Zealand.
The first thing you notice is that so many of the plants and trees are ones you’ve never seen before. That’s because they are. Because of its long biological isolation, plants grow here that are found nowhere else in the world.
The second thing is that everything looks as if it’s out of some dinosaur scene in Jurassic Park. That’s because it is. Indeed, lowland forests in New Zealand have been described as “dinosaur forests” since many of the plants seen in those areas first evolved during dinosaur times.
Finally everything is so green here and full of life even in the middle of winter. We generally think of full-leafed plants as being deciduous, that is, they lose all their leaves every year, and trees such as pine trees being evergreens. But despite almost all the plants here having leaves, only a mere 5% are deciduous. So it is always green.
Here a photo I took last week here in the middle of winter.
And the forests are full of life. Countless vines and plants cling to the trees. Stumps and fallen logs are smothered with flowers, mushrooms and mosses. Streams and waterfalls are everywhere. Strange sounding birds chirp from the forest canopy. You feel the raw pulse of life. In places you feel what the first man or woman must have felt.
But first, a few definitions and background information—
Native means a plant was in New Zealand at the time of human arrival. Endemic means a plant grows in New Zealand and nowhere else in the world. 80% of the New Zealand’s native species are endemic.
New Zealand has more tree species than all of Europe even though it only has 3% of the land surface area.
Before humans arrived, 85% of New Zealand was covered with forests. The Maori burned off anywhere from about one quarter to one half of that, and the Europeans between 1850 and 1950 obliged by destroying (burning or cutting down) half of what remained. Some 30% of New Zealand is currently covered with forest.
And now onto our first plant—
Ponga (Cyathea dealbata), the silver tree fern, is perhaps the most familiar tree fern in New Zealand. It is endemic to New Zealand primarily seen on the North Island and grows to ten meters in height. Walking in the native forests here, one constantly sees this delicate and strangely beautiful plant.
Ponga’s fronds are green on top but have a characteristic silver-white coloration on the underside. Maori used to mark their trails with the white upturned fronds since the underside would remain white and visible for a long period of time and could even be seen readily under moonlight.
Ponga, the silver fern, is also widely used as an unofficial national symbol for New Zealand. While in New Zealand, you see it everywhere.
It is also the logo for a number of industries, organizations and sports teams including New Zealand’s All-Blacks rugby team. There have even been proposals to adopt the silver fern as the flag of New Zealand.
Ferns are ancient plants and New Zealand in unique in having over 200 species about half of which are endemic. Ferns first evolved in the early Carboniferous Period, the so-called age of ferns, period 360 million years ago. Almost all of the ferns from this period became extinct and most of today’s ferns are related to ferns in the early Cretaceous 145 million years ago. Just so you can get your timeline right, dinosaurs lived from 245 to 65 million years ago.
The Sexual Life of Ferns
Ferns reproduce via spores rather than with seeds or flowers. When you see a fern tree you are seeing what’s called the sporophyte form of the plant. All the cells in the sporophyte plant have paired chromosomes just as all the cells in our bodies, except sex cells, have paired chromosomes. Paired chromosomes means two of the same type of chromosome but with differing traits on each one. In humans, one of each of our paired chromosomes comes from our mother and one comes from our father.
In ferns specialized cells split on the fern’s leaves to form spores. Spores only have half of the full compliment of chromosomes, that is, only one of each chromosome now. These spores form in tiny structures on the lower surfaces of the leaves called sori.
The sori break open and spores are released into the air. The spores land on moist soil and grow into tiny separate plants termed the gametophyte form of the fern. This form of the fern plant is only about 0.5 cm wide and is rarely seen. It is also completely separate from the main larger plant.
The gametophyte (the small) form of the fern plant produces both male and female gametes (sex cells) which join together (fertilization) and grow into that large sporophyte plant, in this case the tree fern ponga, that we see. And the cycle repeats itself. What is interesting is that most of us are not aware of this separate tiny form of the plant (and perhaps some of us don’t care!).
This differs from most other plants that we are familiar with. Most plants keep their whole sexual reproduction apparatus on the parent plant in the form of, for example, pine cones or flowers. They don’t have this tiny somewhat precarious form separate from the parent plant and where in a sense all the action takes place.
The scientific name for ponga is Cyathea dealbata. As you may know the scientific name for an organism is always written in italics. The first part of an organism’s name is its genus and the second part is its species. This method of classification was started by Carl von Linné, also known as Carl Linnaeus, a Swedish scientist in the 1700’s. Latin was the scientific language used in that day, hence the names are in Latin. As an aside, it is said that in this tradition, Carl Linnaeus also referred to himself in Latin as Carolus Linnæus.
For ponga, the first part of its scientific name, Cyathea, comes from a Greek word meaning “little cup” relating to a developmental flap of tissue that protects the sori. Dealbata, the second part of the name, means whitened.
The leaves of ferns are called fronds and when they are young they are coiled into a tight spiral called a crozier or fiddlehead which uncoils to form the fern leaves.
This shape, called a ‘koru’ in Māori, is a popular motif in Maori art and a symbol of new life or creativity. The shape is also used in many modern New Zealand designs. A stylized version even forms the logo for Air New Zealand, the airline responsible for getting me here to New Zealand to begin with.