Crocus leaves have a characteristic 'stripe' of chlorophyll free cells down the middle.   The stripe varies in width between species (see below) but is common to almost all taxa.   The leaves may have minute hairs, often along the margins.   The underside of the leaves usually has a keel, which may have grooves alongside it.   These features can be of taxonomic importance.   The number of leaves per corm varies considerably and can be useful in distinguishing between species.   Illustrated below are Crocus hermoneus (few broad dark green leaves with prominent central white stripe) and Crocus pallasii haussknechtii (many narrow grey green leaves with insignificant central stripe.)

Crocus hermoneus leaf - upper surface. A dark green leaf with a wide central stripe.

Crocus pallasii haussknechtii leaves. Note the ciliate (hairy) margins to the leaves.

Crocus hermoneus - few broad leaves

Crocus pallasii haussknechtii - many narrow leaves