Restios are arguably the most under- rated group of fynbos plants, which is surprising as the Restionaceae is the definitive family of plants in fynbos. If there are no naturally-occurring restios in an area, it’s not fynbos.
As I prepared the exhibit of restios for this year’s flower show by the Hermanus Botanical Society, I wondered why these under-rated plants appear so “difficult” that even fynbos enthusiasts shy away from trying to identify them. I suspect it’s because on the whole they don’t have flashy flowers that make identification somewhat easier. Restio flowers are tiny, and are usually obscured from view by brown bracts – and often additionally by more specialised bracts called spathes.
So let’s call a spathe a spathe.
It’s not necessary to name a plant to appreciate it and marvel at its beauty and resilience. So if we don’t get trapped in the details of naming restios, what is interesting about them?
Based on evidence from fossil pollens, the Restionaceae likely originated millions of years ago when the southern continents were still part of Gondwana. When Gondwana split, the areas that now became Australia, South America, India and Madagascar, carried some restios along. That is why there are restio species in Western Australia and a few species in South America, India and Madagascar.
Harsh conditions, like poor soils, wind, drought, hot, dry summers and frequent fires further shaped the plants as we know them today.
When you look at a restio, you may notice that it has no leaves. All that’s left on the stem (called a culm) are a few leaf sheaths, which may or may not fall off with age. In the absence of leaves, the photosynthetic function rests in the green culms. The frilly green stuff you may see at the base of a restio are not leaves, but sterile branches. When a restio is cut, burned or germinates from seed, the first thing it does is to turbo-boost photosynthesis by growing a mass of curly green sterile culms to provide more chlorophyll and increased food synthesis. Then after a year or two it is able to produce the fertile culms that bear the flowers.
If restios are definitive and so dominant in the fynbos biome (despite the fact that they are often overlooked) they must have an important role to play. Nature is never without reason. So what is their role?
The roots of fynbos plants have a secret life about which we know very little; this subterranean world remains under-explored. Many fynbos plants have symbiotic relationships with fungi or bacteria. Bacteria in the soil stimulate many proteas to produce dense clusters of rootlets, called proteoid roots. These dense roots improve the uptake of poorly soluble ions, especially phosphorus, iron and manganese.
These sponge-like proteoid roots have another vital function – they soak up rainwater and release it slowly back into the environment to prevent floods and secure a constant water supply. Restio roots also participate in this water sequestration.
Restionaceae are dioecious, meaning that they have separate male and female plants. They are wind-pollinated; the pollen produced by the male flower sets sail upon the wind to far-distant females. For this reason the flowers don’t need to spend precious resources on attracting pollinators to get the job done. The anthers on male flowers that produce the pollen are boat- shaped so that the pollen doesn’t fall off until the breeze is strong enough to waft the pollen away.
You would think that pollen grains from many different species mixing in the air could perhaps land on the flower of a different species. It could, yes, but only the pollen from the correct species has the right shape and chemical signal to stick to the female restio style for fertilisation to occur. When the female plants are in flower and ready to receive pollen you will often see the styles protruding like brightly-coloured feather boas from the otherwise inconspicuous flowers. For pollination to occur, the chemistry must be just right.
This is the reason why restios do not hybridise.
Restios have evolved various seed dispersal mechanisms. Some restio seeds have a tasty appendage called an elaiosome. Ants collect the seeds with elaiosomes and carry them off to their nests to eat later. The seeds remain safe and protected in the ant nest to germinate when the time is right. This ant-mediated dispersal of seed is known as myrmecochory.
One restio takes the cake for evolutionary excellence. Ceratocaryum argenteum produces large, round nuts that are strikingly similar in appearance, smell, and chemical composition to antelope droppings (in particular those of the eland and the bontebok), which the dung beetles accordingly roll away and bury, effectively sowing a new generation of C. argenteum.
Restios are increasingly popular in horticulture as architectural plants in a similar way that grasses are used. (Restios are not grasses, but reeds.) Some large restio species have been used for thatching and hut building for many centuries.
New research into the chemical composition of the restio Elegia tectorum has shown that it is rich in compounds known to have antioxidant activity. It is not clear yet what benefits it has to the plant, but extracts could be exploited for human use in the “natural health” industry. Furthermore, this restio contains an inhibitor of the enzyme elastase. Why is this interesting? The natural activity of elastase is to break down the protein elastin in the skin, causing the skin to develop deep wrinkles. A small clinical trial has shown that application of E. tectorum extract to the skin reduces wrinkling!
Perhaps our humble restios can one day take the world by storm like rooibos tea did.