Black walnuts in the husk are about two inches in diameter and are shaped like small basketballs. The trees can be identified by their large compound leaves, alternately arranged on the branches. Each leaf has 15-23 leaflets and note in the photo that the terminal leaflet is often missing.
The nut is in clusters of two to five at the end of the branch and ripens in the autumn into a fruit with a brownish-green, semi-fleshy husk and a brown corrugated nut. The whole fruit, including the husk, falls in September and October in the eastern United States. The actual seed is relatively small and very hard.
Introduction to Black Walnut