Shoot performance and population structure in pure stands of Mercurialis perennis L., a rhizomatous perennial herb.

Shoot populations of the rhizomatous perennial herb Mercurialis perennis were studied in pure stands throughout a developmental cycle in a mixed deciduous wood in eastern England. Shoot cohorts exhibited exponential decay between May and October, with half-lives ranging from 2.1 to 7.1 months, although three out of five populations decayed at virtually the same rate. Differences in decay rates were interpreted on environmental grounds. Fertile shoots exhibited higher percentage survival than sterile shoots throughout their growth, and fewer than 5% of them died until well after flowering had been completed. At all dates fertile shoots were significantly taller and heavier than sterile shoots. Shoot growth rates were rapid until tree canopy closure; after canopy closure little change in size occurred. Similarities exist between several aspects of the behaviour of shoot cohorts of M. perennis and Solidago canadensis, another rhizomatous herb.