Abstract
Records of time of flowering obtained from herbarium specimens of Rumex acetosella L. indicated seasonal delays and a shorter period of flowering with increasing latitude and altitude, while earlier flowering was indicated in regions of Mediterranean climate. Observations on the time of flowering in a uniform environment of populations spanning 50° of latitude showed correlations with latitude, and deviations from this trend could be attributed to adaptation to montane, continental, or Mediterranean climates. Experiments showed that the species required long days for floral induction in the seedling year, the populations varying in the length of day required, with populations from high latitudes not flowering in the prevailing daylengths at Christchurch (43° 30′S). In the second year of growth all populations flowered in the prevailing daylength at Christchurch, although long days and high temperatures hastened the maturation of flowers and the populations varied in time of flowering. Population differences in adventitious shoot formation were shown and this was negatively correlated with flowering in both the same year and the following one, and with the height and number of elongated internodes of the panicles. Evidence indicates that populations vary in their ability to flower in the seedling year at their site of origin. This variation is related to differences between the environments, as these affect the establishment and vegetative spread of seedlings and the extent of exclusion of R. acetosella by inter-species competition.