Both deciduous trees and heads of cauliflower might seem to be  solid masses but both are clumps of separate clusters. Each must be shaded relative to its position according to the light source.

During the daytime, the sun is the primary light source. Notice how individual clusters cast shadows on each other.

If the clusters were separated, they would be shaded separately–like individual spheres.

The light source casts light and shade on the trunk, the limbs, and the clusters of leaves

How to Draw and Shade a Winter Tree with Graphite Pencil – Jacki Kellum Tutorial

During the night, the moon is the primary light source outside.

Summer Night – Jacki Kellum Watercolor Painting

The light and shade impacts the grasses. the roads, and the paths, too.