What is miscanthus?
Miscanthus species are woody, perennial, rhizomatous grasses, originating from Asia which have the potential for very high rates of growth. Miscanthus may be familiar to many as a flowering garden ornamental, but it is the sterile, hybrid forms that are of value agriculturally.
Miscanthus growing in the UK
Miscanthus is planted in spring and once planted can remain in the ground for at least fifteen to twenty years. First year growth is insufficient to be economically worth harvesting. New shoots emerge around March each year, growing rapidly in June-July, producing bamboo-like canes. The miscanthus dies back in the autumn/winter, the leaves fall off, providing nutrients for the soil, and the canes are harvested in winter or early spring. This growth pattern is repeated every year for the lifetime of the crop, and the annual harvest gives an annual income to the farmer.
Miscanthus spreads naturally by means of underground storage organs known as rhizomes. However, their spread is slow and there is little risk of uncontrolled invasion of hedges or fields. These rhizomes can be split and the pieces re-planted to produce new plants. All propagation, maintenance and harvest operations can be done with conventional farm machinery, but dedicated miscanthus planters produce the most even establishment. Semi-automatic potato planters can also give excellent results.
In the UK, long-term average harvestable yields from a mature crop (i.e. excluding the first 3 years – see section on yield), have exceeded 16 oven dry tonnes per hectare per year (odt/ha/yr) at the most productive experimental sites. These high yields suggest that the crop has the potential to make an important contribution to the UK’s commitments to energy generation from renewable sources since 22,000 tonnes of miscanthus can provide enough electricity to power 2,000 homes.