Illustrations by Marina Smelik
Leaf shapes can be very useful for identifying plants. It is important to remember though that shape can be somewhat variable even on a single plant. When determining leaf shape, look at many leaves to get a feel for the overall leaf shape represented.
A number of common leaf shapes are illustrated below, but be aware that intermediate shapes also exist. For example leaves may be ovate-lanceolate; not quite ovate or lanceolate, but somewhere in between. In addition, leaves that grow in the shade can have a different shape (large and thin) compared to leaves growing in the sun (smaller and thicker).
There is another consideration when looking at leaf shapes, and that is something called leaf heteroblasty. Leaf heteroblasty refers to different leaf shapes between juvenile and adult growth. It is noticeable in Eucalyptus and other species such as Acacia melanoxylon.
Scale - like. Illustrated is a branchlet with scale-like leaves. Each leaf is about 1/16” (1.5 mm) long.
Awl-like. Illustrated is a branchlet with awl-like leaves, each leaf is typically 1/3 to ½” ( 8 to 13 mm) long.
Needle-like leaves (pine trees). In this illustration, two leaves are present. They are bound at the base by a fasicle.
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