Grasses
Grasses (Family Poaceae) are a significant group of flowering plants that evolved from a common ancestor about 145 million years ago during the Cretaceous period. At that time the dinosaurs were the dominant land animals, some of which grazed on the grasses which were found on the forest edges in moist areas. Towards the middle of this period, the separation of South America, Africa and India from Antarctica-Australia, drove changes to ocean distribution and rain-bearing winds. Then 65 million years ago a global winter, resulting from meteorite showers and volcanic activity that released poisonous sulphur gases into the atmosphere, brought about mass extinction of many species including the dinosaurs. With the colder weather, water became locked up and many forest species could not survive. Grasses began to diversify and expand over vast tracts of land, particularly in America, Africa and Australia. They co-evolved with grazing mammals in these areas. Grasses developed a form of photosynthesis that required less water and so could thrive in arid regions. Today, grasses cover about 20% of the Earth’s surface and are crucial for agriculture, providing staple foods like rice, wheat, and maize. They play a vital role in ecosystems, their roots stabilise soil, preventing erosion, and enrich it with organic matter whilst providing a range of microhabitats that support biodiversity. The sheer global expanse of grasslands is such that they store up to 34% of terrestrial carbon, and because many have deep, resilient roots they can withstand droughts and fires.
Native grasses are an excellent choice for gardens – they have adapted to our climate and impoverished soils, require low to no maintenance, are host plants for up to a quarter of our butterfly species, provide food and/or shelter for a large variety of other insects which in turn support a range of birds, lizards, frogs and small mammals. Tussock and clumping grasses, such as kangaroo grass (Themeda triandra), barbed wire grass (Cymbopogon refractus) and blady grass (Imperata cylindrica) are particularly significant in these roles. Growing to 1 m in height, the latter two species, with their fine foliage and attractive flower and seed stalks, are good specimen plants in small groups in open, sunny locations. All three are impressive in cottage gardens, rockeries, as garden edging or in a mass planting among small grevilleas or native daisies. Placing rocks or a hollow log and a shallow birdbath amongst the grasses further supports the wildlife habitat.
Each clump of blady grass shares an extensive rhizome network that can penetrate the soil up to 1.2 m deep. This grass, therefore, is ideal to grow in areas subject to erosion. In more shady positions or filtered sunlight, weeping grass (Microlaena stipoides) is a good substitute with its brilliant green slender foliage and weeping habit.
Other areas of the garden, such as under a tree, are shady and are more suitable for a stoloniferous or prostrate form. Pademelon grass (Ottochloa gracillima) is a slender, perennial groundcover. It has tiny flowers and forms dense mats. Somewhat similar in appearance, wavy beard grass (Oplismeneus aemulus) prefers a moister habitat. It typically grows to 0.3 m tall and can form large colonies. It can be used as a turf substitute where other grasses will not grow and is useful for planting between stepping stones in shady areas.
