Rooted cuttings of four American sycamore clones (Platanus occidentalis L.) were used to investigate early tree growth, leaf development, and dry-weight production for a short-rotation plantation in east-central Mississippi. Monthly increments in height and diameter growth were measured during the second (1990) and third (1991) growing seasons in the field. Peak rates of monthly growth for height were 49 cm in 1990 and 73 cm in 1991, while peak monthly diameter growth rates were 6.1 mm in 1990 and 5.9 mm in 1991. Monthly changes in number and length of branches, number of leaves per tree, and leaf area per tree were taken during 1990. Leaf expansion rates of the leaves on primary branches were determined in 1991. Peak monthly branch growth occurred early in the growing season (June) and was 10.5 m tree(-1). Numbers of leaves per tree continuously declined from 588 in May to 257 in November. Early leaves were smaller than leaves at later measurements, however, so that leaf area reached a maximum of 15 m(2) tree(-1) in August. Leaf expansion rate peaked at 7.5 cm(2) branch(-1) day(-1) in May, and declined to almost zero after August. Monthly height and diameter increments were linearly correlated with number of leaves per meter of tree height (r = 0.64 for height and 0.83 for diameter) and with leaf area per meter of tree height (r = 0.56 and 0.64). Neither clonal differences nor month-by-clone interactions were detected for average monthly height and diameter growth in 1990 and 1991. Numbers and yearly growth increments of branches per tree were also not different among clones, but significant month-by-clone interactions were related to one clone's rapid branch growth early in the growing season. This clone also produced more leaves and larger leaf area per tree than the other three clones during that period. Dry weight of the three-year-old trees averaged 15.9 kg tree(-1), which included stem, roots, and branches. The stem-plus-branch dry weight was 9.4 kg tree(-1). Because the plantation was planted at a 1.2 x 3.7 m spacing and had 94% survival, the stem-plus-branch dry weight represented 20.4 Mg ha(-1) at age three (3.0 dry tons ac(-1) yr(-1)). Significant clonal differences were found only for branch dry weight per tree. Branchy clones may be best for maximum dry-weight production in short-rotation sycamore plantations. (C) 1996 Elsevier Science Ltd.