Early leaves covered with dense hair. Small seedling very similar to common ragweed, but giant ragweed cotyledons are three to four times larger and green underneath instead of purple. To top Grass Key Top of page 24. Both cotyledon margins are entire, and cotyledons are covered on both surfaces with short hairs. The stem is densely hairy.
True leaves are heart-shaped and alternate with serrated margins and velvety, hairy surfaces.
To top Grass Key Top of page 25. Seedling is small, pale green and only sparsely hairy. First leaves have very pointed tips and petioles. Hypocotyl is slender and often reddish. To top Grass Key Top of page 26.