Fruit size was only marginally smaller in one season, but Brix levels appeared to improve as trees aged. Six year old Aoshima trees on Flying Dragon produced fruit with Brix levels of 11.7, compared to 10.9 in fruit from trees on standard trifoliata. Acid levels were not altered by rootstock, but better fruit colouring was evident on trees on Flying Dragon. There is now much commercial interest in Flying Dragon, but because of the problem of high off-type numbers in seedling populations, experimentation has begun on tissue culturing of this rootstock. Tree spacing and yields Most of the citrus orchards in Japan are on steep, terraced hillsides.
Land area is the major limiting factor, and high density planting is carried out.
The commercial life of an orchard is considered to be 30-40 years. In the Mikkabi district which we visited, yields for satsuma mandarins average 15 tonnes per hectare. Only in plantings older than 10 years are yields of 30 tonnes per hectare achieved. All satsuma trees are fruit thinned after natural drop has finished. A second thin is carried out a month later, and sometimes a third 'fine tuning' thin is needed another month later.