Purple moonflower's (Ipomoea turbinata Lagasca y Segura) vegetative growth and seed maturation were characterized in noncompetitive field studies. Seedling emergence of 50% or greater of mature scarified seed occurred to a soil depth of 12 cm. At vegetative maturity a typical plant produced 11 primary, 50 secondary, 94 tertiary, and 7 quaternary runners having a total length of 185 m. The average number of leaves per plant was 1,120. Maximum seed size, seed wet weight, occurrence of first mottled seed, and first capacity to germinate occurred 20 days after anthesis in immature seed that were removed from the seed pod. Maximum germination occurred at 26 days after anthesis. Seed moisture content (dry weight basis) reached 8.5%, seed had formed an impermeable seed coat, and physiological maturity (defined as maximum dry weight) occurred 34 days after anthesis. The total number of purple moonflower seed produced per plant averaged 9350. The major mechanism of seed dormancy was impermeability of seed coats.