Juvenile growth is the period from the seedling to first flowering as an adult.
This may be as short as 3-4 weeks for some quick-growing ephemerals such as Ranunculus sessiliflorus or at least 10-15 years for trees like Eucalyptus crebra, Eucalyptus moluccana and Eucalyptus tereticornis. For many of the perennial groundcover species it is probably of the order of 3-6 months.
During the juvenile period many of the herbaceous species develop thickened rootstocks that allow them to survive in drier conditions. The long-lived shrub Bursaria spinosa, Blackthorn, develops a similar thickened rootstock during its early juvenile period. Once this is developed, the juveniles may persist for years in suboptimal conditions (e.g. from competition or grazing) before being able to mature.
Successful juvenile growth needs the right conditions, primarily moisture, and space. Our observations are that most juvenile growth takes place after periods of extended good rainfall, in autumn and spring, often in relatively open sites, often bared by previous surface disturbance, drought or fire. Mortality of juveniles in hot dry periods is high.