Plants of Populus euramericana (Dode) Guinier Robusta were grown in sub-irrigated, gravel-filled containers under conditions of constant temperature and irradiance. Lengths of leaves and internodes and diameters of internodes were measured three times a week. Dates of internode maturation were estimated from the growth curves of the internodes. At these dates, the length of the elongating portion of the shoot, or growing shoot (GS), could be determined. The growing shoot increased in length as a function of plant age. The diameter of GS was related to its length. The relationship between the volume of GS and both the absolute growth rate of a branch and the architecture of the vascular system are discussed.