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Northern Ontario Plant Database
Leaf Terminology
General Leaf Terminology
| Simple leaf |
an undivided leaf, with a single blade. |
| Compound leaf |
a divided leaf, separated into 2 or more leaflets. |
| Trifoliate |
a plant with 3 leaves, e.g., trilliums (Trillium, Melanthiaceae). |
| Blade |
the flat, usually photosynthetic portion of the leaf. |
| Petiole |
the stem of the leaf. |
| Midrib or midvein |
the main vascular strand of a leaf (leaflet). |
| Secondary Veins |
econdary ascular strands that branch off the midrib. |
| Stipule |
pairs of small leaf-like structures located at the base of a petiole. |
| Stipulate Leaf |
a leaf with stipules. |
| Exstipulate Leaf |
a leaf without stipules. |
| Adaxial Surface |
the upper surface, the surface facing the stem. |
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| Abaxial Surface |
the lower surface, the surface facing away from the stem. |
Compound Leaf Terminology
| Leaflet |
one segment of a compound leaf. |
| Petiolule |
the stem of a leaflet. |
| Rachis |
the main axis of a pinnately compound leaf, appearing as an extension of the petiole. |
| Rachilla |
the secondary axis of a compound leaf. |
| Pinnately Compound |
a compound leaf with leaflets arranged opposite each other. |
| Bipinnate |
a twice-pinnately compound leaf, with each leaflet pinnately divided. |
| Tripinnate |
a thrice-pinnately compound leaf, with each series pinnately divided. |
| Palmately Compound or palmate leaf |
a compound leaf with all the leaflets attached at the same point at the end of the petiole. |
| Unifoliolate |
a leaf with a single leaflet and a petiolule distinct from the petiole, formed from the loss of remaining leaflets of a compound leaf, e.g., redbud (Cercis, Fabaceae). |
| Geminate or bifoliolate |
a leaf with 2 leaflets arising from the same point. |
| Ternately Compound |
a compound leaf with leaflets arranged in multiples of 3. |
| Ternate or trifoliolate |
a compound leaf with 3 leaflets, e.g., clover (Trifolium, Fabaceae). |
| Biternate |
a leaf divided into 3 main divisions, each of which is divided into 3 leaflets. |
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