Varieties of the ornamental grass miscanthus have become a coveted ‘designer plant’ around the world in recent years. The graceful habit and fine texture of miscanthus add interest to any style of garden, be it formal, cottage, woodland, Asian, Mediterranean or xeriscape (arid). The ever-changing mood of the grass through its growth cycle—from the ‘explosion’ of fresh green shoots of early spring through to the shimmering seed-heads and rich orange-yellow tones of autumn—brings a reminder of the fleeting nature of the seasons.
Wild Miscanthus species are distributed through parts of eastern and southern Asia, Pacific and Africa. Several species are native to Japan, of which ‘susuki’ or Miscanthus sinensis (variously known in English as maiden grass, silver grass, fairy grass, feather grass) is the most widespread. The Japanese have traditionally regarded the silvery flower panicles of susuki as a harbinger of autumn, and the grass is counted among the so-called ‘Seven Wildflowers of Autumn’ (‘Aki-no-Nana-Kusa’). Susuki is also celebrated in the poems of the 8th-century Japanese classic ‘Man’yōshū’ or ‘Collection of Ten Thousand Leaves’.
The relationship between the Japanese and miscanthus goes back much further, however. As the main source of roofing thatch, miscanthus has been used since the prehistoric Jōmon period over 10,000 years ago. Before the advent of industrial agriculture in the mid-20th century, miscanthus was also used as a source of fertiliser, mulch and stockfeed. Miscanthus was an integral part of the traditional Japanese ‘satoyama’ system, in which natural resources were carefully managed to support environmentally sustainable agriculture and living—typically, miscanthus would be harvested for roof re-thatching, and the old thatching material would then be recycled as fertiliser for the fields. Miscanthus was such a valued commodity that communities all around Japan used to have managed plots of miscanthus grassland called ‘kayaba’—the financial district of Kayabachō in central Tōkyō derives its name from the abundance of miscanthus and reeds in the originally swampy landscape of the area.
Kayaba plots were tended with the same care bestowed on edible crops, with particularly strict rules on the timing of harvesting so that the grasslands remained productive year after year. Fresh growth was encouraged and invasion by woody plants controlled through burning of the grassland at the end of winter, in a similar way to how the Aboriginal people in Australia managed the grasslands—perhaps not so surprising given that some anthropologists believe that the Jōmon people, the ancestral Japanese race, were descended from the same wave of people who arrived in southern Asia some 70,000 years ago, and continued their journey to the southeast to become the Australian Aboriginal people…
Miscanthus grows densely and rapidly, making it one of the most prolific producers of organic matter in the plant world. Its hard stems and sharp-edged leaves, combined with the carbohydrate and protein-rich pith found inside the reed-like stems, result in slow breakdown of the organic matter by microbes, gradually returning the nutrients to the soil—in effect, a natural slow-release fertiliser—as well as attracting beneficial soil organisms such as earthworms. The high silica content of miscanthus leaves and stems discourages plant diseases and pests, protecting crops grown in soils enriched with miscanthus-derived humus. Miscanthus leaves and stems also make the perfect mulch as their coarse, interlocking texture prevents soil erosion, while forming a dense, moisture-retentive mat that protects the roots of crops from temperature extremes and drying out. A true all-rounder, indeed!
I have used miscanthus mulch in my gardens in Australia and the results have been quite obvious—the most impoverished soils have been transformed into dark, humus-rich soils (the worms love it!), and the humus has a peculiarly fine, somewhat spongy texture that has greatly improved both the soil structure and moisture retention. In fact, without miscanthus, the vast areas of young volcanic terrain found throughout Japan would not have turned into lands that support lush forests and agricultural activity. Miscanthus is typically the first plant to colonise fresh lava flows and ash deposits after a volcanic eruption. The strong root system of miscanthus breaks apart the solid rock and compacted ash, while debris from the above-ground growth builds up organic matter in the soil. Miscanthus is not affected by the nutrient imbalance in young volcanic soils that can be lethal to many plants—and its growth has the effect of balancing soil nutrition over time. After some 500 to 1000 years of miscanthus growth, the initially barren terrain can finally be colonised by tree saplings, transforming the grasslands into forests—some of which have been cleared to become productive agricultural land that have fed the Japanese for centuries.
With modernisation, the relationship of the Japanese with miscanthus that had evolved over thousands of years finally unravelled. As solid roofing materials replaced thatch and tonnes of chemical fertilisers replaced slow-release organic fertilisers, miscanthus grasslands were abandoned. The area of grasslands in Japan has shrunk by 95% in the last 100 years, as unmanaged grasslands reverted to forest. The situation is ironic in that Japan now faces a dire shortage of roof thatching material required for restoration of heritage buildings, while scientific research suggests that miscanthus grasslands are highly effective in sequestering atmospheric carbon in the current world of changing climate...
So, the next time you see a miscanthus plant at your local nursery, it’s not just another pretty ornamental plant you are looking at, but an amazing grass that sustained a culture for thousands of years…
HOW TO GROW MISCANTHUS: Full sun to part shade, but leaf tips may burn in full sun during very hot and dry weather. Not suitable for shaded areas, as the stems become leggy and tend to fall over. Tolerates practically any well-drained soil type, though better structured soils and an acid pH will result in a more pleasing appearance (no fertilising required, however). Requires regular moisture until established, then is heat and drought tolerant (no watering required except in very dry climates). Fully frost and snow tolerant—dies down to ground level in winter in colder climates, semi-evergreen to evergreen in warmer climates with year-round rainfall (e.g. Sydney). Requires cutting back to the ground once a year in winter before new spring growth. Allow plenty of space around each plant for the larger varieties (which can reach a height of over 2 metres with a similar spread); for confined spaces, select dwarf cultivars such as Miscanthus sinensis ‘Adagio’ that grow to about 1 metre height with a tight clumping habit.
USING MISCANTHUS IN YOUR GARDEN: Suits a wide range of garden styles, paring well with many different types of plants. Taller varieties make a great background screen for the warmer months, sheltering lower-growing foreground plants from the hot sun, while allowing in more light when cut down to the ground in winter. They also provide a focal point around the edge of a garden pond, as often used in Japanese stroll gardens. Taller variegated varieties pair particularly well with large-foliaged plants (e.g. palms) for a ‘tropical’ look in cooler climates. Smaller varieties are versatile in mixed plantings, e.g. in cottage gardens, meadow gardens, and rockeries, where it provides textural contrast and depth of perspective. They also make spectacular soft-textured edging to pathways with the autumn display of flower panicles, seed-heads and foliage colour. In Japanese gardens, smaller miscanthus varieties are often used in combination with other autumn-flowering plants such as Platycodon (balloon flower), chrysanthemum, and Lespedeza (bush clover) to provide a seasonal accent, and to balance hard garden elements such as stone washbasins and bamboo fences.
POTENTIAL WEED RISK: Miscanthus sinensis is a declared prohibited pest plant in the Australian Capital Territory, where it is an offence to plant, propagate or sell all varieties of this plant. No restrictions apply in other areas of Australia, however, Miscanthus sinensis is considered an environmental weed in New South Wales (especially the Blue Mountains). If in doubt, please check with authorities in your local area before planting. Cutting off the seed-heads before they fully mature at the end of autumn will minimise the risk of self-seeding (dispose of the collected seed-heads using the council green-waste collection, not your own compost pile). If you live near bushland, sterile and near-sterile varieties (e.g. Miscanthus sinensis ‘Variegatus’, Miscanthus sinensis ‘Cabaret’, and Miscanthus x giganteus) are strongly recommended. Some tall Australian native grasses and sedges have a similar appearance to miscanthus and produce good quantities of organic matter to enrich your soil, e.g. spear grasses (Austrostipa spp.), tall sedge (Carex appressa). These native species may be a better choice where miscanthus poses a high weed risk.