Tree ID by triangular leaf. 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.

Tree ID by triangular leaf – Poplars and Birches – Black, Hybrid and Lombardy Poplars, Silver, Downy, West Himalayan, River, Erman’s and Swedish Birches. Click on any photo to enlarge it. To go back to the Broadleaf Leaf Key click HERE. To go back to the Tree Identification Keys click HERE. Click on a name in BLUE to get more information on these trees.

Black Poplar leaf

Black Poplar

Hybrid Black Poplar leaf

Hybrid Black Poplar

Lombardy Poplar leaf

Lombardy Poplar

Downy Birch leaf

Downy Birch

West Himalayan Birch

West Himalayan Birch

River Birch leaf

River Birch

Erman's Birch leaf

Erman’s Birch

Erman's Birch leaf

Swedish Birch

On broadleaf tree leaves the leaf stalk is referred to as a petiole by botanists. The petiole connects the leaf to the shoot. If the leaf has no petiole and sits right on the shoot it is known as sessile. The leaf blade is divided down the centre by the midrib. This is the central or main vein of the leaf. The veins are tubes that carry water and nutrients to and from the leaf surface. The network of veins reaches every part of the leaf surface. The leaf blade is also referred to as the lamina. The edge of the lamina is called the leaf margin. The shape of the leaf is determined by how the margin and the veins develop and is under precise genetic control. 

The margin may be smooth, toothed or lobed. There are growth points along the margin which are aligned with veins. Smooth margins grow at a uniform rate  but toothed leaves have parts of the margin that are distant from the growth points and lag behind resulting in the formation of teeth. If the growth between the tips is inhibited even more, a lobe is formed. A lobe is a rounded or pointed segment of a leaf that is separated from other segments by a gap that does not reach the midrib of the leaf. Lobes may be arranged on either side of a central axis like a feather. This leaf is ‘pinnately lobed’, or lobes may spread radially from a point like a hand.This leaf is ‘palmately lobed’. If the gap reaches the midrib the leaf is ‘palmate’. If growth between tips is further inhibited a ‘pinnate’ leaf may be formed. This has individual leaflets arranged either side of a midrib like a feather.

The shape and colour of the leaf, the number and arrangement of the veins, the size and complexity of the teeth and the shape and arrangement of the lobes are genetically controlled and offer an excellent means of identifying trees.