A new tea-plant must grow for five years before its leaves can be picked and, at 30 years of age, it will be too old to be productive. The trunk of the old plant must then be cut off to force new stems to grow out of the roots in the coming year. By repeated rehabilitation in this way, a plant may serve for around 100 years. The season of tea-picking depends on the local climate and therefore varies from area to area. A skilled picker can only gather 600 grams (a little over a pound) of green tea leaves in a day.