pment have been quite variable. This variability in growth has been attributed to seedling quality. Seedlings with large root-collar diameter achieve the best growth, and planting seedlings with a root-collar diameter of less than 6 mm is not recommended. In Georgia Piedmont bottomland site, seedlings at age 7 ranged in height from 3.8 to 6.2 in. after 7 years on a strip mine in Indiana, sweetgum averaged 2.1 in. on favorable sites in the lower Mississippi Valley, and seedling height growth of .6m/yr has been reported. On upland sites, 5- year growth varies considerably, from 1.1 in on an eroded field to 2.0 in. on areas reverting to woody cover. It is slow, early growth of sweetgum plantations that is of concern to silviculturists because it necessitates expensive cultivation to reduce weed competition and thereby maintain acceptable survival until height growth begins. First-order lateral root morphology of Nursery-lifted sweetgum seedlings reflects their future competitiveness in the field. Early growth and survival can be acceptable. Even in moderate to severe drought years, if nursery-lifted seedlings have 5 or more first-order lateral roots exceeding 1mm in diameter at the junction with the taproot. As many as one third of all seedlings in selected families growing in one nursery did not meet these standards making them poorly competitive in a forest environment.Trees begin to produce seeds when 20 to 30 years old and continue production until at least 150 yrs of age. Seed production varies widely depending on climatic conditions during the growing season. Under optimum conditions, seed balls may average as many as 56 sound seeds per ball, or as few as 7 or 8 under less favorable conditions. Seed balls have been collected for more than 12 yrs at the Forestry Sciences Laboratory, Athens, Georgia and scientists there expect 20 to 30 sound seeds per ball in an average year but have found as few as 5 per ball in a bad year. Low perc...
