The petiole wing, explained
In citrus, the leaf stalk is called the petiole, and on many species it carries a small leafy extension called a wing. The size and shape of that wing is the most reliable leaf-level identifier in the whole genus.
A lime typically has a narrow to moderate wing. A lemon usually has a narrow wing or none at all. A grapefruit or pomelo has a broad, almost heart-shaped wing that is nearly as wide as the leaf. Kaffir lime barely has one.
Citrus leaves compared
| Citrus | Leaf size | Petiole wing | Other clues |
|---|---|---|---|
| Tahitian lime | Medium, oval, glossy | Narrow to moderate | Few thorns, very glossy dark green |
| Kaffir lime | Small, doubled hourglass shape | Almost none | Distinctive two-lobed leaf, very aromatic |
| Lemon | Medium to large, pale green | Narrow or absent | Paler, less glossy leaf, strong thorns |
| Mandarin | Small, narrow, glossy | Very narrow | Slim leaves, almost no thorns |
| Orange | Medium, oval, glossy | Narrow to moderate | Leaves with a slightly winged stalk and few thorns |
| Grapefruit | Large, rounded | Broad, heart-shaped | The wide wing is unmistakable |
Other leaf features worth checking
- Gloss. Lime leaves are usually the glossiest of the common citrus, with a hard shine. Lemon leaves are noticeably duller and paler.
- Shape. True lime leaves are oval with a rounded tip. Lemon leaves are longer and more pointed.
- Thorns. Limes are often nearly thornless, while lemons carry long, sharp thorns on vigorous growth.
- Aroma. Crush a leaf. Lime is sharp and clean; lemon is softer and more floral; kaffir lime is intensely perfumed and lingers on your fingers.
- Leaf arrangement. Citrus leaves alternate along the stem, but kaffir lime leaves grow in a doubled shape that looks like two leaves joined end to end.
Kaffir lime is the one you cannot mistake
Kaffir lime, also called makrut lime, has a leaf unlike any other citrus. The blade is pinched in the middle into an hourglass shape, as though two leaves were fused at the waist. There is almost no petiole wing.
If the leaf is a clean double-lobed shape and smells strongly of lime when crushed, that is the identification. These leaves are the ones used in Thai and Indonesian cooking, and unlike other citrus leaves they are meant to be eaten.
What leaves cannot tell you
Leaves get you to a shortlist but they cannot always name the variety. Tahitian and Mexican lime have very similar leaves, and many lemon varieties are indistinguishable from each other on foliage alone.
If you need the variety, wait for fruit or take a photo of the fruit, the flower and the leaf together. A flower is the single most useful addition, because citrus flowers differ in size, colour and how they are clustered.
Citrus trees are grown far more often than they are labelled, and a lime that has lost its tag is easy to confuse with a lemon, especially before either fruits. Leaves are the fastest way to tell them apart, and one feature does most of the work: the little flare of leaf tissue where the blade joins the stalk.
This guide covers the leaf features that matter, how the common citrus compare, and why kaffir lime is the odd one out.
Frequently Asked Questions
Lime leaves are glossier, darker green and more oval with a narrow winged stalk. Lemon leaves are paler, duller and more pointed, and lemon trees usually carry longer, sharper thorns.