In order to establish a strong and high-yielding crop, miscanthus care is generally important in the early stages of establishment. Once the crop is fully established and has gained some protection from weeds and weather, the amount of care required reduces considerably.
Miscanthus growth cycle
Giant Miscanthus (miscanthus x giganteus) is a biomass crop that has a very regular annual cycle and demands little maintenance once the crop is mature. Establishing the crop as mature will take 2 to 3 years at which time the crop can be harvested in the very early spring allowing it to grow again and be re-harvested at a similar stem length the following year. The crop will start growing in spring and continue throughout the summer. Once growth slows and ceases in the autumn, surplus nutrients, held in the stems, start to move back down towards the rhizome in the ground for winter storage. This assists in the reduction in moisture of the harvested crop allowing it to be baled soon after cutting. The whole process is repeated with the mature rhizomes growing fresh shoots that are harvesting again the following year. This will repeat annually for as many as twenty years.
Miscanthus does not grow during the winter months. In preparation for the coldest season, the nutrients in miscanthus crops retreat to the rhizome under the soil. Crops that have just been planted, so have grown through one summer, will not need to be cut back in year one. The initial rate of growth at this time is lower than subsequent years. Under normal seasonal weather conditions the first harvest can take place after two years. Mature crops will grow to harvestable heights annually as the shoots will have a higher rate of growth.
Division and propagation of miscanthus
Giant miscanthus is a hybrid sterile crop and as such does not reproduce through pollination. In order to create new fields of freshly grown plants, rhizomes must be propagated through division and then replanted.
Agricultural best practice for miscanthus, based on previous results, is for the rhizome dividing to done with mature actively growing crops whilst in the field. It can also be done through separately potted plants grown in greenhouses, these are known as “plugs”. The most effective reproduction results have been achieved in the field with crops that are 2/4 years into the long term growing cycle of growth and harvest. Rhizomes that are too young or several years older do not achieve the same levels of successful reproduction once replanted. Those of four to five years old can have as high as an 88% success rate and multiply long term production yields several fold.
How to divide the miscanthus rhizome
Rhizome division takes place early in the year, ideally after the last frost of the winter and when suitable soil conditions allow, in the UK it will usually be before the rhizomes have started to produce buds. The process will have an effect on the established or “mother crop” in terms of next year’s harvest but it will allow as many as ten other fields to be planted resulting in overall yields multiplying several-fold dependant on conditions and the success rate of the replanting process.
For successful miscanthus propagation, a blade is first used to cut the rhizomes, growing just under the surface soil, from the deeper more established roots. This process is known as “undercutting”. Once complete the rotivator can be brought in to break up the rhizomes into smaller pieces that are then harvestable. These pieces are lifted from the ground and need to be sorted by size. The selected pieces are then put into a place of cold storage with a temperature of 3 to 5 degrees Celsius. This facility will keep the rhizomes available for transplanting for up to 3 months. Alternatively, if the fields to be newly planted are nearby and have been prepared, they can be planted straight away.
Miscanthus x giganteus grass care
The time of most vulnerability in farming giant miscanthus plants is in the early stages of development. The initial care and attention in preparing the ground properly for first year planting is essential in minimising the risks at this time. Site selection processes, the judicious use of herbicides, rotivating the soil, carefully spacing the plants in the ground are all practices that will all assist in managing the crop through the initial two year establishment phase. The use of fertilisers can be an aid at this stage but are generally not a necessity. If ideal soil has been selected creating the best conditions for cultivating a long term successful crop they need not be used.
Miscanthus develops natural defences throughout this time. The layer of mulch produced from the leaves discarded by the plants during the autumn reduces weed plant growth that tend to compete for nutrient. The height of the plants themselves minimise the levels of sunlight that reach the soil surface, again discouraging any invasion form unwanted plant growth.
The plants used in forming the hybrid naturally grow in Asia. Miscanthus crops that are grown in Europe have yet to be subjected to any form of predator or disease,. Fertilisers have been used to feed miscanthus crops, mainly to increase nitrogen content on some soil types or to replace Potash following several years of crop removal. Additional fertilisers are not always necessary especially if ideal growing conditions can be created from the start through good pH soil content and an adequate water supply. Once into year three and beyond crop care is really about observation and careful monitoring.