Many trees have triangular or diamond-shaped leaves that differ slightly but can be used to identify the species. Here are eight images of triangular or diamond-shaped  leaves.

Black Poplar leaf

Black Poplar

Hybrid Black Poplar leaf

Hybrid Black Poplar

Lombardy Poplar leaf

Lombardy Poplar

Silver Birch leaf

Silver Birch

Downy Birch leaf

Downy Birch

West Himalayan Birch

West Himalayan Birch

River Birch leaf

River Birch

Erman's Birch leaf

Erman’s Birch