Phragmites communis rhizomes grow during the autumn, but buds develop nearly all the year round. For much of the year the buds remain dormant near the soil surface, and then in spring there is a period of rapid emergence which lasts from between a few weeks to nearly 4 months. Apart from replacements of frost-killed shoots, few buds emerge during the rest of the year. Emergence starts at the end of the period of internal dormancy if the weather is warm enough. In Britain it is not, and there is about a month of temperature-controlled dormancy. Emergence can be delayed further by unusually unfavourable conditions of temperature or water-supply. Exposure to frost kills some shoots, but stimulates bud development and lengthens the emergence period. Burning and severence of rhizomes break internal dormancy. Cutting does not, and so is very damaging if carried out directly after the emergence period, since no replacement crop is then produced, and so that plant is unable to photosynthesize during half of the growing season.