Ailanthus reproduces both sexually and asexually. Asexual reproduction is by vegetative sprouting from stumps or root portions (Hu 1979). Flowering occurs rather late in the spring (June). Ailanthus has the longest winter dormancy of all the trees in its native Chinese habitat (Hu 1979). Precocious flowering is not a rare occurrence in this species and has been observed in seedlings only 6 weeks after germination (Feret 1973).
Seeds ripen in large crowded clusters from September to October of the same year and may persist on the tree through the following winter (Little 1974, Hu 1979). An individual tree can produce 325,000 seeds per year which are easily wind-dispersed (Bory and Clair-Maczulajtys 1980). These seeds average over 30,000 per kilogram. This amount yields up to 6-7000 "usable plants" (Little 1974). Limited testing of ailanthus seeds indicate that they have dormant embryos, and that germination is benefited by stratification on moist sand for 60 days at 41 F (Little 1974).
Seedlings establish themselves rapidly by producing a well formed tap root in less than three months (Adamik and Brauns 1957). In more compacted soils these seedlings put forth long rope-like lateral roots to exploit a greater soil volume (Rabe and Bassuk 1984). Ailanthus grows quickly in full sunlight and averages a meter of growth in height per year for at least the first 4 years (Adamik and Brauns 1957). The trees may grow to 15-20 meters tall but have a rather short lifespan of less than 50 years (Adamik 1955).