。
The tree is casting its shadow on the wall.
Literal
Tree [topic-は] wall [on-に] its shadow [object-を] is-casting.
影を投げかける ('to cast a shadow') is the standard collocation — literally 'to throw up a shadow.' 投げかける is itself a compound verb (投げる 'throw' + かける 'hang/put over'), adding the sense of 'throwing upon.' The possessive その ('its') refers back to 木 — using その rather than 木の in this kind of descriptive writing is smoother and more natural.