The flowers have three stamens and a gynoecium of three united carpels and an inferior ovary, three locules and axile placentation with fruit that is a loculicidal capsule.

[2] Crocus is an acaulescent (lacking a visible lower stem above ground) diminutive seasonal cormous (growing from corms) herbaceous perennial geophytic genus.

[3] The corms are symmetrical and globose or oblate (round in shape with flatted tops and bottoms), and are covered with tunic leaves that are fibrous, membranous or coriaceous (leathery).

The leaves have a distinctive shape in cross-section, being boat-shaped with two lateral arms with margins recurved inwardly towards the central ridged keel, forming the sides of the "boat".

The bases of the cataphylls form the corm tunic, and their number varies from 3 to 6, and enclose the true leaves (euphylls), bracts, bracteoles and flowering stalk.

The seed surface is highly variable, including papillate (covered in small protuberances), digitiform (finger-like) and other epidermal cell types.

[18][19] While the flowers may vary dramatically between species, there is little variation in the leaves,[20] but sufficient variability in corm tunics that they may be used as an aid in differentiating taxa.

[30] Similar accounts are found in continental European herbals, including those of l'Obel in Flanders (1576)[31] and Besler's Hortus Eystettensis in Bavaria (1613).

Jussieu (1789) placed the genus Crocus in his Ordo (family) Irides or Les iris, as a member of the class Stamina epigyna (stamens inserted above the ovary) as part of the monocotyledons, the first level of the division of the flowering plants.

[29] By the late 19th century Maw (1886),[47] following Herbert, subdivided the genus into two divisions, the Involucrati and the Nudiflori, and then further divided it into six sections and lastly by flowering times (spring or autumn).

These series were defined by the division of the style, the corm tunic, flowering time, leaf structure, presence of a bracteole and anther colour.

[60][29] Crocus populations have extremely high infra-specific variability with a very diverse spectrum of morphological and phenotypical varieties, while many individual specimens from different species may closely resemble each other.

The authors state, "further studies are required before any firm decisions about a hierarchical system of classification can be considered" and conclude "future re-classification is likely to involve all infrageneric levels, subgenera, sections and series".

[64] A further study, using the internal transcribed spacer region (ITS) of the nuclear ribosomal DNA (rDNA), together with a chloroplast marker, broadly confirmed these findings.

Flowering season did not correspond to molecular groupings and nor did any of the previously used morphological characteristics, indicating a high degree of homoplasy, in which traits are gained or lost independently in different lineages.

[72][73] Pulsatilla species, which are commonly called pasqueflowers, unlike crocuses have rhizomes, the foliage is covered with long soft hairs, and the flowers are produced on above-ground stems.

[47][79][80] Crocuses are distributed from the Mediterranean, from the Iberian peninsula and North Africa, through central and southern Europe, the islands of the Aegean, the Middle East and across central and southwest Asia to Xinjiang in western China, but most species are restricted to Turkey and Asia Minor and the Balkans, with the Balkan Peninsula having the largest number of species (at least 31),[59] forming the centre of diversity, however they are widely introduced.

[83][20] The majority of species are native to areas with cold winters and hot summers with little rain, and active growth is typically from fall to mid-spring.

[14] The natural habitats of crocus species are threatened by human activities, including urbanization, industrialization, and other land disturbances and recreational uses.

[47] In its first year, the crocus produces only a single leaf and creates a corm covered by a thin tunic, about 5–8 mm in size, dependent on the species.

[10] As the fruit capsule ripens, it emerges from the soil at the base of the flowering stem before dehiscing (splitting open) and releasing the seeds.

Modern saffron production is widely cultivated in Kashmir, Iran, Turkey, Afghanistan and the Mediterranean from Spain to Asia Minor.

[101] Crocuses were described in Turkish gardens in the early sixteenth century,[102] gathered from the far reaches of the Ottoman Empire,[103] where they were seen by visiting European botanists and explorers, among the first of whom was Pierre Belon who arrived in Constantinople in 1547.

Jehan Somer, a Middelburg merchant, brought back crocuses among his other specimens in 1592, where they attracted the attention not only of Clusius but of the early Dutch flower painters, notably Ambrosius Bosschaert.

[107] Crocuses are among the most important ornamental geophytes in the global flower industry,[108] ranking sixth in terms of Dutch bulb production (2003–2008) with 463–668 ha under cultivation.

[111] The varieties cultivated for decoration in gardens and pots mainly represent six species: C. vernus, C. chrysanthus, C. flavus, C. sieberi, C. speciosus and C. tommasinianus.

[88] Autumn-flowering species of crocus that are cultivated include:[85] C. laevigatus has a long flowering period which starts in late autumn or early winter and may continue into February.

[119] The carotenoids found in the styles of Crocus species, particularly C. sativus have been shown to inhibit cancer cell proliferation, and have led to interest in potential pharmaceutical applications.

[120] Theophrastos (4th century BC) described the saffron crocus as being valued as a spice and dye, while Homer compares a sunrise to the flower colour.

Bosschaert, working from a preparatory drawing to paint his composed piece spanning the whole of spring, exaggerated the crocus so that it passes for a tulip, but its narrow, grass-like leaves give it away.