Seed size and weight significantly affected witchweed [Striga asiatica (L.) Kuntze = S. lutea Lour. ♯4 STRLU] seed germination, witchweed emergence, and host-parasitization. Witchweed seed were divided into four groups for testing; large (> 149 microns in diameter) and heavy (specific gravity greater than one) (LH), large and light (specific gravity less than one) (LL), small (< 125 microns in diameter) and heavy (SH), and small and light (SL). Germination percentages were 87, 84, 58, and 26 for LH, LL, SH, and SL, respectively. Corn (Zea mays L.) was planted in pots containing soil infested with these four seed categories. The total number of witchweed plants (submerged plus emerged) per pot containing LH, LL, SH, and SL witchweed seed was 65, 12, 0, and 0, respectively, and the number of witchweed plants that emerged was 19, 4, 0, and 0 per pot. There were no significant differences in shoot weights of corn grown in the pots either between kinds of witchweed seed infesting the soil or between plants grown in infested soil and plants grown in soil that did not contain witchweed seed. Roots of corn plants grown in soil infested with LH seed were significantly heavier than those grown in soil infested with any other seed class and heavier than those from soil that did not contain witchweed seed. No other seed class significantly affected root weight.