Shadows looking weird


i’m trying to learn jMonkeyEngine. For this, i’ve created something like an island. Unfortunately, the shadow isn’t working :(.

The shadow on the grass looks weird. The shadows on the leaves aren’t correct. And the grass as well as the leaves of the palm trees are only shadowed at one side.

The grass is made with the forester. The palm trees are some models i’ve added in the editor. I’m using the Pssm shadow.

Can anybody give me a hint how to fix this?