Leaf venation

Illustrations by Marina Smelik

Leaf venation refers to the pattern of veins on the leaf. The veins supply the leaf with water and minerals from the roots and transport materials from the leaf to the rest of the plant. The vein pattern can be useful for plant identification when the pattern is distinct and obvious, so only a few basic patterns will be used in this course.

                                    LEAF VENATION PATTERNS

The primary vein is like the trunk on a tree. It is the widest vein on the leaf and starts at the base of the leaf.

Secondary veins are like the main branches on a tree, they are smaller than the primary vein.

There are two ways the secondaries may come off the primary. In one pattern, illustrated on the left below, the secondaries come off of the primary vein all along the length of the primary. In the second pattern, illustrated on the right below, secondaries originate from at or near the base of the primary.                          

Leaf secondary veins all arising along entire length of primary vein.
Leaf secondary veins (at least some) arising at or near leaf base.

Secondary veins parallel to each other for their entire length, stay straight all the way to the leaf margin.

Secondary veins parallel to each other for their entire length, curve upward as they approach the leaf margin.
Leaf secondary veins not parallel to each other for their entire length, secondary veins much-branched.

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The secondary veins can also create a pattern that can be helpful for identifying certain plants. Again, the pattern must be distinctive and obvious to be of use. Here are three patterns: