Relations among surficial materials, light intensity, and sycamore-seed germination along the Potomac River near Washington, D.C.

Seed of sycamore, a common tree on river flood plains, germinate in mineral soil exposed to high light intensities. Germination rates are low on surfaces covered with leaf litter, and seedlings die when shaded by closely spaced herbaceous plants. All germination rates were higher when seed were kept moist. Surflcial materials and light values in this study are similar to those on flood plains. Results were derived from counting seedlings after planting 1,000 seeds in each of several flats filled with different kinds of flood-plain and upland soils.