Leaves come in many shapes and sizes. This is a brief introduction to seven details on a simple leaf that can help with plant identification.

1. The colour

It is incredible just how many shades of green exist. If we take the three leaves from the previous post, we can see that the Sage leaf is greyish-green, the centre of the Holly leaf is a dark green and the Gingko leaf is a yellowish-green. The green colour in leaves is due to the pigment chlorophyll, which plays an important role in photosynthesis.

Colours may differ on the top side and the under side of a leaf, for example in the case of the mature Bramble leaves (Rubus fructicosus) on the left. However, young bramble leaves, which contain high levels of antioxidants [1], are a much lighter colour and together with young bramble buds can be foraged in early spring.

2. Shape

Ginkgo leaves, as seen above, have a unique fan-shape. Extracts from these extraordinary leaves have been shown to have a number of health benefits including improving circulation and heart health, and delaying the progress of dementia and diabetes [2]. Other more common leaf shapes include linear, lanceolate, oval, reniform (kidney-shaped), deltoid and cordate (heart-shaped).

3. Margin

The edge or margin of a simple leaf can be entire which means smooth without any indentations, dentate or tooth-like, or even wavy with sharp spines.

4. Tip

Variations in leaf tips include acute, truncated, rounded and aristate.

5. Base

The base of the leaf can also be rounded or truncated. Other possibilities include cordate (heart-shaped) and cuneate (wedge-shaped).

6. Attachment to the stem of the plant

How the leaf is attached to the plant can also provide a clue to its identification. The leaves of Epilobium angustifolium (Rosebay willowherb) on the left have no stalk and are directly attached to the stem so they are "sessile". "Pedunculate" leaves grow directly from a stalk or peduncle, as in the example of Populus nigra (the Poplar tree) on the right.

7. Veins

Leaf veins are small channels that transport nutrients and liquid to the leaf cells. They also provide a skeleton to structure the leaf. In some leaves the veins run parrallel to each other and in others, for example the sage leaf to the left, they branch out from the central vein (the "midrib"). On other leaves several primary veins radiate from a single point.

The above list far from exhaustive. Indeed, many other factors, such as the texture and smell of the leaf and its arrangement on the plant, can also provide useful hints as to plant identification. We will be exploring some of these features in future posts. In the meantime, enjoy the huge diversity of foliage around us!

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[1] Wang SY, Lin HS. Antioxidant activity in fruits and leaves of blackberry, raspberry, and strawberry varies with cultivar and developmental stage. J Agric Food Chem. 2000;48:140–6

[2] Isah T. Rethinking Ginkgo biloba L.: Medicinal uses and conservation. Pharmacogn Rev. 2015 Jul-Dec;9(18):140-8.