Sword gasses or sword sedges are native in Australia. I was introduced to them by a veteran volunteer firefighter. He did not like them. Why. Let us take it from far to close.
Gahnia is one of the maligned grasses. It is easily seen in open areas. It sends up seed spikes that are 2 metres (6 feet) or more tall. When mature, the spikes are dark, almost black. They are like warning flags. Black for danger. But many of these grasses also occur in woodlands. These first two pictures are taken along the track of an occasional stream – the availability of water is suggested by the bright green vegetation around the dark flags.
Below, a little closer. The grasses form clumps. The clumps expand as the plants age. Clumps with younger seed-heads are of a softer colour.
Gahnia is a kind of sedge or rush – plants that often put up stiff stems that carry the seeds. There are about 40 species occurring naturally in a broad geographic region that extends from New Zealand to China. Several of the species that occur in Australia – Gahnia melanocarpa (the black-fruited saw sedge), Gahnia erythrocarpa, Gahnia clarkei (tall saw-sedge), and Gahnia sieberiana (the red fruited saw-sedge) – are all tall and generally similar in appearance. The lighting of the plant on the left shows that the seed head is red. The plant was also found beside a small river. It is one of the more common species near Sydney in Australia – Gahnia sieberiana (the red fruited saw-sedge).
As with many other plants that live in habitats with frequent fires, many sword-sedges flower after a fire.
The ‘swordiness’ of Gahnia comes from very sharp fine teeth on the leaves. Some, such as the cricket, exploit them for grip. As they extend from the base, the leaves roll up. They are like files. They rasp and cut the skin. Before good protective gear was available, fragments of stems would get into the clothing of firefighters. As the firefighters moved and worked, so the leaves would work into their clothes and would cut into their skin. For this reason, they were not much loved.
Going even closer reveals that these stems are the home to small red animals. They are often hidden among the roots or within the curved up leaves, but when stressed, they will emerge and walk round the leaves looking for a better home. These are flat mites, related to spiders and like spiders they have 8 legs. At the front (top, right) is a short feeding proboscis.
This ‘Far too Close!’ item is set in the context of ‘Nature’s Envelope’ – the envelope of all things and all processes that make up biology. Biology involves objects from photons to the atmosphere around Earth. A range of 20 orders of magnitude of size. Processes may be brief events lasting less than a femtosecond, or be the 3.5 billion years of evolution. That covers over 30 orders of magnitude of duration. The envelope is a simple grid showing these sizes and durations in orders of ten-fold magnitude. This tale is a window into this grid that starts with a landscape of several kilometres, narrowing down to plants that may be several metres tall, then dealing with their leaves (5-10 mm), and finally with mites about one tenth of a millimetre in size. The window provides evidence of events that can be measured in seconds (the ambling of the mites), to those that take years (large clumps of sword-sedge). That is, the endurance of the processes range over about 8 orders of magnitude of time. The numbers are inexact. Yet, the example illustrates the power of the visual to reveal intricacy and complexity across a wide spectrum of Biology.