This article is about the genus of flowers. For the myth of the youth Crocus who was turned into a crocus, seeCrocus (mythology). For other uses, seeCrocus (disambiguation).
They are low growing plants, whose flower stems remain underground, that bear relatively large white, yellow, orange or purple flowers and then become dormant after flowering. Many are cultivated for their flowers, appearing in autumn, winter, or spring. The flowers close at night and in overcast weather conditions.
The crocus has been known throughout recorded history, mainly as the source ofsaffron. Saffron is obtained from the driedstigma ofCrocus sativus, an autumn-bloomingspecies. It is valued as aspice anddyestuff, and is one of the most expensive spices in the world. Iran is the center of saffron production.
Crocuses arenative to woodland, scrub, and meadows from sea level toalpine tundra from theMediterranean, throughNorth Africa, central and southernEurope, the islands of theAegean, theMiddle East and acrossCentral Asia toXinjiang in westernChina. Crocuses may be propagated from seed or from daughter cormels formed on the corm, that eventually produce mature plants. They arrived in Europe from Turkey in the 16th century and became valued as anornamental flowering plant.
Crocus display the general characteristics of familyIridaceae, which include basal cauline (arising from the aerial stem) leaves that sheath the stem base,hermaphrodite flowers that are relatively large and showy, the perianth petaloid with two whorls of three tepals each and septal nectaries. 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 anacaulescent (lacking a visible lower stem above ground) diminutive seasonal cormous (growing fromcorms)herbaceous perennialgeophytic genus.[3] The corms are symmetrical andglobose oroblate (round in shape with flatted tops and bottoms), and are covered with tunic leaves that are fibrous, membranous orcoriaceous (leathery). The corms produce fibrousroots, and contractile roots which adjust the corms depth in the soil, which may be pulled as deep as 20 centimetres (8 in) into the soil.[4][5] The roots appear randomly from the lower part of the corm, but in a few species, from a basal ridge.[6]
Plants produce several basal linear bifacial greenleaves that arise from the corms. These areadaxially (upper surface facing axis) flat or channelled with pale median stripes, while the opposite (abaxial) surface is strongly keeled, with two grooves on either side. 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 keel may be square or rectangular, but is lacking inC. carpetanus. The pale central stripe is caused byparenchymatous cells which lackchloroplasts and may contain air spaces.[7] The leaves are from 5 to 30 millimetres (3⁄16 to1+3⁄16 in) wide and 10 to 118 centimetres (4 to 46 in) long. The leaf-likebracts are membranous, while the smaller bracteoles are either membranous or absent.[4][5] The leaf bases are surrounded by up to 5 membranous sheaths calledcataphylls, a specialised leaf. 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.[8][9]
The number ofpeduncles (flowerstems) vary from one to several and remain underground, emerging only at the fruiting stage, bearing flowers that are solitary or several, so that a truescape is absent. The flowers arepedicellate (attached to the peduncle by a short subterranean pedicel stalk). The pedicel is sometimes subtended (below pedicel) by a membranous, sheathingprophyll (leaf-like structure).[4][5]
The showy, salver to cup-shaped, single or clusteredactinomorphic flowers taper off into a narrow tube; the flowers emerge from the ground, and can be white, yellow, lilac to dark purple, orvariegated incultivars. The flower tube is long, cylindrical and slender, expanding apically. Thefloral tube is long and narrow with 6 lobes in 2whorls. Theperianth is 3+3 (3 sepals+3 petals) andgamophyllous (with fused segments). Thetepal whorls are similar, equal or subequal with a smaller inner whorl, and cupped to outspread. The bracts are membranous, but the inner ones are sometimes lacking.[4][5][10]
The 3stamens are erect and linear and inserted in the throat of the perianth tube, with anthers shorter than the filaments.Pollen grains are inaperturate (apertures absent) but sometimes spiraperturate (spiral shaped).[11] Each flower has a singlestyle which isexserted (projecting beyond thecorolla tube) and slender distally with three to many branches. The branches are highly variable, being short or long, and simple, bifurcate (dividing in two) or multifid and sometimes distally flattened. The inferiorovary has 3 carpels withaxile placentation. It remains underground, and as theseeds ripen, thepedicel (stem of the flower) grows longer so thefruit is above the soil surface.[4][5][12]
The fruit is a small membranouscapsule, ellipsoid or oblong-ellipsoid in shape and the manyseeds are globose to ellipsoid. The seed surface is highly variable, includingpapillate (covered in small protuberances),digitiform (finger-like) and other epidermal cell types. In some species the seeds arearillate, with fleshy appendages. Crocus seeds have both inner and outerinteguments and in some species the outer epidermis may display long papillae.Embryo-sac development is Polygonum type.Dehiscence (splitting of the capsule to release the seed) is of theloculicidal type in which it splits through the wall of the locules leaving the septa that separate them intact.[13][10][14]
Crocus has extensiveaneuploidy (abnormal number of chromosomes), with some uncertainty as to the basenumber of chromosomes. The chromosome numbers shows extreme variability, ranging from 2n=6 to 2n=70 even within a single species.[15][11]
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 differentiatingtaxa.[21]
The crocus was well known to the ancients,[22] being described at least as early asTheophrastus (c. 371 – c. 287 BC),[a][24] and was introduced into Britain by the Romans, where the saffron crocus was used as adyestuff. It was reintroduced into Western Europe by theCrusaders. The crocus is mentioned in mediaeval and laterherbals, one of the earliest being the 14th centuryTractatus de Herbis.[25][26]William Turner (1548) states that the crocus is referred to as saffron in English, implying that onlyC. sativus was known at that time.[27] However, by 1597John Gerard writes of "sundry sorts" and uses the term saffron and crocus as interchangeable. He included both spring and autumn flowering crocus, but distinguished Wild Saffron (Crocus) from Meadow Saffron (Colchicum). He described eleven forms. Some of his specimens were obtained fromClusius.[28][29] In the following century,John Parkinson in a more detailed account was more careful to include separate chapters forColchicum, with the common name of meadow saffron, fromCrocus or saffron. Parkinson (1656) states that there are "divers sorts of saffrons" describing 27 spring flowering plants and 4 autumn flowering ones, pointing out that only one of those was the true saffron crocus, which he calledCrocus verus sativus autumnalis.[30] Similar accounts are found in continental European herbals, including those ofl'Obel inFlanders (1576)[31] andBesler'sHortus Eystettensis inBavaria (1613).[32]
The genusCrocus was first formally described byLinnaeus in 1753, with threetaxa, and two species,C. sativus (type species),var.officinalis (now treated as a synonym ofC. sativus) and var.vernus (nowC. vernus) andC. bulbocodium (nowRomulea bulbocodium). Thus Linnaeus recognised two taxa that are accepted as separate species in modern classifications, one vernal and one autumnal crocus, but incorrectly assumed they were only varieties of a single species, while his second species was actually from a closely related genus that was only recognised later (1772).[33] However, a subsequent re-examination of Linnaeus's specimens suggested the presence of several different species that he did not recognise as being separate.[34]Linnaeus' system, based on sexual characteristics,Crocus was classified as Triandra Monogynia (Threestamens, Singlepistil).[35] Linnaeus's system was supplanted by the "natural" system which used ahierarchy oftaxonomic ranks based on weighting of the importance of structural characteristics of the plant.Jussieu (1789) placed the genus Crocus in hisOrdo (family) Irides orLes iris, as a member of the classStamina epigyna (stamens inserted above the ovary) as part of themonocotyledons, the first level of the division of theflowering plants.[36]
One of the first monographs of the genus appeared in 1809, byHaworth,[37] followed in 1829 by that ofSabine,[38][29] andHerbert in 1847.[39] In 1853,Lindley continued the placement ofCrocus as one of 53 genera inIridaceae, which he included in a higher order of monocotyledons, the Narcissales.[40]Baker published a monograph on the genus in 1874, adopting a very different schema to that of Herbert.[41] In 1883,Bentham and Hooker described the Irideae (Iridaceae) as having more than 700 species, and divided it into 3 tribes and further into subtribes.Tribe Sysyrinchieae as having 2 subtribes, including Ixieae. The latter wascircumscribed with four genera,Crocus,Syringodea,Galaxia (Moraea) andRomulea.[42] This circumscription has remained stable since, with the exception ofMoraea which properly belongs in a separate tribe. The most influential monograph of the nineteenth century was that ofMaw (1886), which forms the basis of modern understanding of the genus. Maw built on the work of Herbert, rejecting Baker's classification.[43] The availability of molecular phylogenetic methods in the late twentieth century has shown that the Iridaceae properly belong within the orderAsparagales.[44]
The scientific study of the genus in the late eighteenth century was accompanied by detailed descriptions withBotanical illustrations, such as those ofWilliam Curtis (1787) andSims (1803),[45] that appeared inCurtis's Botanical Magazine, with illustrations bySydenham Edwards.[46] Other illustrations are found inmonographs such as those ofHaworth (1809)[37] andSabine (1830), illustrated byCharles John Robertson.[38] The largest collection is found in the most comprehensive monograph, that of Maw (1886).[47] Other sources include the portfolios of plates, such as the survey of the plants of France byMasclef (1891). At that time onlyC. sativus andC. vernus were included in theFlora of France.[48]
The genusCrocus belongs to themonocotfamilyIridaceae (iris family), specifically the large subfamilyCrocoideae. Within that subfamily, crocus is placed on thetribe, Ixieae (synonym Croceae),[b] one of five. The Ixieae are then subdivided into subtribes, with the generaCrocus,Romulea andSyringodea forming subtribe Romuleinae. The Romuleinae have been characterised within the Ixieae by progressively reduced aerial stems.[51] solitary flowers on the stem branches and woody tunics on the corms. They also often have divided style branches. However,Crocus corm tunics are fibrous and membranous rather than woody as inSyringodea. Also,Crocus has a ridged and often keeled abaxial leaf surface, while that ofSyringodea is rounded, and the midline adaxial translucency ofCrocus is lacking inSyringodea.Romulea is principally distinguished from the other two genera by generally having aerial stems or at least an ovary at ground level, compared with the other acaulescent genera, other differences include unifacial rather than bifacial leaves and the pollen structure.[52][51]
Within the Romuleinae,Crocus is asister group toSyringodea, the two genera forming a sister group toRomulea.[49][53][15]
The genus Crocus consists of about 200 accepted species, which continue to increase, and has undergone a large number oftaxonomic classifications.[29] The genus has often been divided intosections, beginning with that of Haworth (1809)[37] who described two sections based on the presence or absence of hairs in the throat of the flower, while Sabine was the first to realise the importance of the presence or absence of a basal spathe (prophyll) in dividing the genus into two sections,[38] a practice followed by Herbert.[39] However, Sabine's practice of using trinomials forvarieties such asC. sulphureus concolor is no longer accepted, although Herbert somewhat similarly used varieties and subvarieties, e.g.C. vernus var.1Communis subvar. 1.Obovatus. Herbert also used geographical distribution as a basis of classification.[29] By the late 19th centuryMaw (1886),[47] following Herbert, subdivided the genus into two divisions, theInvolucrati and theNudiflori, and then further divided it into six sections and lastly by flowering times (spring or autumn). Although rejecting the concept of subvarieties, he placed even more emphasis on geography.[54][15][55][29]
The most widely accepted system, that proposed byBrian Mathew in 1982[56] was based on Maw's system, but with less emphasis on flowering times. This mainly depended on three character states:
the presence or absence of a prophyll (a basalspathe);
The genus, as described by Mathew, consisted of two subgenera,Crocirus (monotypic forCrocus banaticus) andCrocus including the remainder of the species, based on whether theanthers were introrse or extrorse (dehiscence directed towards or away from centre of flower) respectively. SubgenusCrocus was then divided into two sections,Crocus andNudiscapus, based on the presence or absence of the prophyll. Each section was then further divided into sixseries ofCrocus and nine ofNudiscapus. These series were defined by the division of the style, the corm tunic, flowering time, leaf structure, presence of abracteole and anther colour. Mathew also introduced the concept ofsubspecies, including 50 in all, by giving similar but differentforms subspecies status if geographically separated, resulting in about 140 distinct taxa.[15] The seven species and ten subspecies discovered since then have been integrated into revisions of this classification, though new species continue to be described,[57][58][59][53] leading to estimates of at least 200 species.[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. Based on such morphological differences between isolated populations many new species have been named, but without a definition of new species based on molecular and/or karyological information, species can not be confirmed, creating difficulties in determiningspeciation and hence the exact number of species.[61][62] The situation is even more complex oncehybridisation (combination of taxa) andintrogression (transfer of genetic material) are considered.[63][29]
The availability ofmolecular phylogeny methods revealed problems with the traditional systems based onmorphology alone. The first analysis of the complete genus was carried out by Mathew and colleagues in 2008 usingnucleotide sequences fromplastid regions. In particular, the DNA data suggest there are no grounds for isolatingC. banaticus in its own subgenusCrociris, though it is a unique species in the genus. Because it has a prophyll at the base of the pedicel, it therefore would fall within sectionCrocus, although its exact relationship to the rest of the subgenus remains unclear.[53]
Of the 15 series in the Mathew scheme, only seven weremonophyletic, and in particular the largest series,Biflori andReticulati, which include a third of all species, were non-monophyletic. Another anomalous species,C. baytopiorum, should now be placed in a series of its own, seriesBaytopi.C. gargaricus subsp.herbertii has been raised to species status, asC. herbertii. The autumn-floweringC. longiflorus, thetype species of seriesLongiflori (long regarded by Mathew as "a disparate assemblage"), appeared to lie within seriesVerni. In addition, the position ofC. malyi was currently unclear.[53]
DNA analysis and morphological studies suggest further that seriesReticulati,Biflori andSpeciosi are "probably inseparable",C. adanensis andC. caspius should probably be removed fromBiflori,C. adanensis falls in a clade withC. paschei as a sister group to the species of seriesFlavi andC. caspius appears to be sister to the species of seriesOrientales.[53][15]
The study showed "no support for a system of sections as currently defined", although, despite the many inconsistencies between Mathew's 1982 classification and the current hypothesis, "the main assignment of species to the sections and series of that system is actually supported". 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 theinternal transcribed spacer region (ITS) of the nuclear ribosomal DNA (rDNA), together with achloroplast marker, broadly confirmed these findings.[15]
Crocus forms a monophyleticclade, with a basalpolytomy of four subclades. The first clade (A) corresponding to sectionCrocus, but includingC. sieberi and several closely related species (originally included in sectionNudiscapus seriesReticulati). The remaining three clades (B-D) include all the remaining species of sectionNudiscapus. Of these, B and C are small, corresponding to seriesOrientales andCarpetani respectively, with all remaining series in the large D clade. The exception isC. caspius, originally in seriesBiflori, whichsegregates in clade B. Thus, although division of the genus into two sections is well supported, no single morphological character defines these two groups. TheC. sieberi group are assumed to have lost their prophyll secondarily. Of the series, eight could be shown to be monophyletic;Crocus,Kotschyani andScardici (sectionCrocus) andAleppici,Carpetani,Laevigati,Orientalis andSpeciosi (sectionNudiscapus). Flowering season did not correspond to molecular groupings and nor did any of the previously used morphological characteristics, indicating a high degree ofhomoplasy, in which traits are gained or lost independently in different lineages. The remainder of the series could not be supported as natural groupings. Mathew's concept of subspecies status withinC. biflorus could not be supported, each being considered a separate species, resulting in the genus having at least 150 species.[15]
A more detailed molecular and morphological study of seriesVerni (sectionCrocus) allowed it to be better characterised and circumscribed, as well as the closely related seriesLongiflori. SeriesVernisensu Mathew was found to consist of two groups, the first beingC. vernussensu Mathew and the other consisting ofC. etruscus,ilvensis,kosaninii andlongiflorus. The taxonomic status ofC. vernus had been uncertain for some time, given the observation that the name was more properly applied toC. albiflorus,[34] requiring a new designation ofC. neapolitanus for those previously known asC. vernus. SubsequentlyC. vernus was split into 5 separate species. The incorporation ofC. longiflorus into seriesVerni resulted in making seriesLongiflori no longer a legitimate taxonomic unit.[60]
In sectionNudiscapus, seriesReticulati was polyphyletic with species intermingled with seriesBiflori andSpeciosi, requiring a recircumscription, confiningReticulati to 8 species, to obtain monophyly.[65] Among the thereby displaced species, are a number of very closely related taxa, referred to as theCrocus sieberi aggregate, which has been proposed as a new seriesSieberi.[29] Other new series, such asIsauri andLyciotauri, continue to be created out of theBiflori series.[66][67]
Mathew's circumscription ofCrocus introduced the rank of subspecies, of which the largest number (14) were those ofCrocus biflorusMiller, the type species of seriesBiflori, a number which continued to grow. Molecular methods identified these as apolyphyletic assemblage rather than closely related subordinate infraspecific taxa. This necessitated a complete taxonomic revision of seriesBiflori, elevating each subspecies to species status.[61] A similar issue occurs withC. reticulatussensu Mathew, who created two subspecies, resulting in 9 newly defined species.[65]
The classification of Brian Mathew (1982), as amended in 2009 divides the genus into two sections, further divided by series.[64] The number of series, continues to evolve.
Some crocus species, known as "autumn crocus", flower in late summer and autumn, during (autumnal) rains, after summer's heat and drought. The nameautumn crocus is also often used as a common name forColchicum,[68] which is not a true crocus but in its own family (Colchicaceae) in the lily orderLiliales. The plants are toxic, but have medicinal uses.Colchicum are also known asmeadow saffron, though truesaffron is not toxic.[69]Crocus species have three stamens whileColchicum species have six;[70] crocus have one style, whileColchicum have three.[71][10]
SomePulsatilla species are also called "prairie crocus" (previouslyAnemone patens) or "wild crocus", but they belong to the buttercup family (Ranunculaceae).[72][73] Pulsatilla species, which are commonly called pasqueflowers, unlike crocuses haverhizomes, the foliage is covered with long soft hairs, and the flowers are produced on above-ground stems.[74][75]
"Crocus", the name of the genus, isLate Middle English (late 14th century) and also denotes saffron. It is derived via Latincrocusfrom theGreek κρόκος (krokos),[76] which is itself probably aloan word from aSemitic language, related toHebrew כרכוםkarkōm,[77]Aramaic ܟܟܘܪܟܟܡܡܐkurkama, andArabicكركمkurkum, meaning saffron (Crocus sativus), "saffron yellow" orturmeric (seeCurcuma), another yellow dye.[78] The word ultimately traces back to theSanskritkunkumam (कुङ्कुमं) for "saffron". The English name is a learned 16th-century adoption from the Latinsafranum, but Old English already hadcroh for saffron, introduced by the Romans.[47][79][80]
Distribution map of 16 species of genusCrocus in Europe and Asia
Habitats range from sea level to as high as subalpine altitudes, and in a wide range of habitats from woodlands to meadows and deserts, often on stony mountain slopes with good drainage.[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. They are negatively impacted by uncontrolled gathering and heavy grazing by livestock.[84]
Successive stages of germination from seed to seedling (G Maw)
Thelife cycle ofCrocus species begins with theseed,germinating to aseedling, and a mature plant in 3–5 years, however seeds may remain dormant in the soil for several years. The germination stages were first described and illustrated by Maw in his 1886 monograph.[47] In its first year, the crocus produces only a single leaf and creates acorm covered by a thin tunic, about 5–8 mm in size, dependent on the species. In the northern hemisphere, the autumnal crocuses flower between September and November. The vernal (spring) crocuses flowering time depends both on climate and habitat, but is usually mid-winter to spring. Leaves may besynanthous (produced during flowering) orhysteranthous (when the flowers wither away).[85] In the summer, with hot and dry conditions the plant becomes dormant, with all the above ground parts dying back. Colder temperatures in winter then activate the corms.[9] Propagation occurs sexually by seed and asexually by small corms, called cormels or cormlets, produced in the axils of the corms (between tunic scales and body of corm).[10] As the fruit capsule ripens, it emerges from the soil at the base of the flowering stem beforedehiscing (splitting open) and releasing the seeds.[86] Seed dispersal may be enhanced by ants, at least in species witharillate seeds.[18]
The economic importance of the genus is largely dependent on the single species,Crocus sativus, now known only in cultivation.[94]C. sativus is grown for the production ofsaffron, an orange-red derivative of its driedstigma, and among the most expensive spices in the world.[53] The estimated worldwide production ofC. sativus plants is 205 tons.[8] About 180,000 stigmas from 60,000 flowers are required to produce 1 kilogram (2.2 lb) saffron, which sells for about US$10,000 (2018). Modern saffron production is widely cultivated inKashmir, Iran, Turkey, Afghanistan and the Mediterranean from Spain to Asia Minor.[8] An important center is theeponymous town ofKrokos, in the Kozani region of Greece. The saffron product, Krokos Kozanis is a PDO (Protected Designation of Origin).[95][96] Production is largely indigenous and Iran accounts for 65% of global production, covering 72,162 ha.[8]
Saffron is thought to have been used inembalming inAncient Egypt. It is mentioned in theOld Testament, in theSong of Songs as a precious spice and has featured as a dye and fragrance throughout written history, with mention in theIliad.[8]
Cultivation and harvesting ofC. sativus for saffron was first documented in the Mediterranean, notably on the island ofCrete.Frescos showing them are found there at theBronze AgeMinoan site ofKnossos, as well as from the comparably agedAkrotiri site on theAegean island ofSantorini,[97][98] and formed an important part of the Minoan economy and culture and had both a sacred role and use as apsychoactive drug andfood additive.[99][100][8] Women still gather crocuses in the Akrotiri region.[101]
Crocuses were described in Turkish gardens in the early sixteenth century,[102] gathered from the far reaches of theOttoman Empire,[103] where they were seen by visiting European botanists and explorers, among the first of whom wasPierre Belon who arrived in Constantinople in 1547. The first crocus seen in theNetherlands, where crocus species were not native, were from corms brought to Vienna in 1562 from Constantinople by the Holy Roman Emperor's ambassador to theSublime Porte,Ogier Ghiselin de Busbecq. A few corms were forwarded toCarolus Clusius at thebotanical garden inLeiden.[20] These were almost certainly cultivated varieties rather than wild species.[104] European visitors to Turkey continued to bring back specimens for gardens in their own country. Prominent among the latter were the gardens atMiddelburg in the Netherlands. 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, notablyAmbrosius Bosschaert.[105][106] By 1620, new garden varieties had been developed, and featured in contemporary illustrations, such as that ofCrispijn van de Passe in hisHortus floridus of 1614.[105] There are accounts of crocus gardens in the seventeenth century, such as the Saffron Garth of Walter Stonehouse atDarfield, Yorkshire.[107]
Crocuses are among the most importantornamentalgeophytes in the global flower industry,[108] ranking sixth in terms of Dutch bulb production (2003–2008) with 463–668 ha under cultivation.[109] The crocus is one of the most popular flowers found in the garden in the late winter and early spring.[20] About 30 of the species are cultivated, among the most popular beingC. chrysanthus,C. flavus,C. sieberi,C. tommasinianus andC. vernus, together with hundreds of cultivars derived from them.[20][8] Both fall and spring blooming crocuses are cultivated for their flowers.[110] Among the first flowers to bloom in spring, their flowering time can vary from fall to the late winter bloomingC. tommasinianus; the earliest fall blooming species,C. scharojanii, may flower during the last weeks of July.[111]
The varieties cultivated for decoration in gardens and pots mainly represent six species:C. vernus,C. chrysanthus,C. flavus,C. sieberi,C. speciosus andC. tommasinianus. During the horticulture production year 2009/2010, more than 70 cultivars were grown in Holland, covering an area of 366hectares; the most common ones were 'Flower Record' and 'King of the Stripes' which accounted for 42 hectares, other species grown includedC. chrysanthus,C. tommasinianus, andC. flavus - all are spring blooming plants.[112] But the most commonly grown plants are the Dutch hybrids with large flowers in a rich palette of colors.[113]
Both sexual and asexual means are used to increase the number of plants; seeds and multiplication of corms are the most common means of production, buttissue culture can be used,[114] most commonly for saffron crocus. New corms are formed on top of the older corm which withers away, and cormels are produced from axillary buds.[112] The production of new plants begins with harvested corms in late June to early July, after being graded by corm size the corms are stored around 22 Celsius until early October when they are moved to 17 Celsius until planted later in October and November; flowering occurs in March and the flowers are not removed. Crocuses are also forced to produce flowering plants out of season and the most common species used areC. vernus andC. flavus, and most of the corms used for forcing come from the Netherlands.[115]
Spring flowering types are planted in fall, while fall-blooming types in late summer; typically, the corms are placed 3 to 4 inches deep in well-draining soil in areas with full sun exposure. They do not thrive in heavy clay soils or those that are damp, especially during their summer dormancy period.[116] Commercial crops are produced on raised beds and slopes, to ensure adequate drainage, while horticulturalists often plant on sand beds for the same purpose.[117] Spring flowering types also do well in areas with deciduous trees, where they flower and produce leaves before the trees completely leaf-out. Crocuses are grown in USDA winter zones 3–8.[118] Not all species are hardy in the upper zones;C. sativus is winter hardy in USDA zones 6 through 8, andC. pulchellus is hardy in zones 5 through 8.[92]
Some are suitable for naturalizing in grass, but mowing off the foliage before it turns yellow produces short lived plants. Some crocuses, especiallyC. tommasinianus and its selected forms and hybrids (such as 'Whitewell Purple' and 'Ruby Giant'), seed prolifically and are ideal for naturalizing. They can, however, become weeds inrock gardens, where they will often appear in the middle of choice, mat-forming alpine plants, and can be difficult to remove. Crocus flowers and leaves are protected from frost by a waxy cuticle; in areas where snow and frost occasionally occur in the early spring, it is not uncommon to see early flowering crocuses blooming through a light late snowfall.[88]
C. laevigatus has a long flowering period which starts in late autumn or early winter and may continue into February.
Colchicum autumnale is commonly known as "autumn crocus", but is a member of the plant familyColchicaceae, and not a true crocus (of the family Iridaceae).
The corms of crocuses have been used as foodstuffs in Syria.[119] The carotenoids found in the styles ofCrocus species, particularlyC. sativus have been shown to inhibit cancer cell proliferation, and have led to interest in potential pharmaceutical applications.[15]
The crocus or krokos has been known since ancient times, and used indecorative arts, such as theMinoan wall paintings in Santorini from ca. 1,600 BC.[97] Representations of the saffron crocus appear frequently in Minoan art[99] and pervade Aegean art from theEarly Bronze Age to theMycenaean period.[120]Theophrastos (4th century BC) described the saffron crocus as being valued as a spice and dye, whileHomer compares a sunrise to the flower colour.[121] Saffron coloured robes were much admired by women in antiquity[122] and gave the garment Crocota its name.[123] The oil was also valued as a cosmetic.[124] According to Greek legend Crocus orKrokus (Greek:Κρόκος), was a mortal youth the gods turned into a plant bearing his name, the crocus, after his death caused by his great desire and unfulfilled love for the shepherdessSmilax.[125] Other versions state that as he died three tears fell into the flower becoming its three stigmata.[126][95]
Crocuses occur in many flower paintings, one of the earliest being that ofAmbrosius Bosschaert'sComposed Bouquet of Spring Flowers (1620). In this painting the cream-colored crocus feathered with bronze at the base of the bouquet reflected varieties on the market at that time. 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.[citation needed]
The crocus is used in many contexts to symbolically denote spring and new beginnings. For instance, it was used as the emblem of the2019 FIFA U-20 World Cup inPoland to symbolise the emergence of new talent.[127]
^As a perfume (ἀρωμάτων) "καὶ πρὸς τούτοις τὸ κρόκινον· βέλτιστος δ' ἐν Αἰγίνῃ καὶ Κιλικίᾳ (the saffron-perfume; the crocus which produces this is best in Aegina and Cilicia)". He also refers to the crocus as a spice (at 34), the word being interchangeable for either use[23]
^Goldblatt originally described this tribe in 2006,[49] but in 2011 renamed it Ixieae, having discovered that this name had precedence[50]
Kafi, Muhammad; Kamili, Azra N; Husaini, Amjad N; et al. (2018). "An expensive spice saffron (Crocus sativus L.): A Case Study from Kashmir, Iran and Turkey". In Ozturk, Munir; Hakeem, Khalid Rehman; Ashraf, Muhammad; Ahmad, Muhammad Sajid Aqeel (eds.).Global Perspectives on Underutilized Crops.Springer Nature. pp. 109–150.ISBN978-3-319-77776-4.
Hill, Lewis; Hill, Nancy (2012) [2003]."Crocus".The Flower Gardener's Bible: A Complete Guide to Colorful Blooms All Season Long: 400 Favorite Flowers, Time-Tested Techniques, Creative Garden Designs, and a Lifetime of Gardening Wisdom (10th Anniversary ed.). North Adams, MA:Storey Publishing. p. 249.ISBN978-1-60342-807-1.
Parkinson, John (1656)."Crocus saffron".Paradisi in Sole Paradisus Terrestris, or, A Choise Garden of All Sorts of Rarest Flowers with their Nature, Place of Birth, Time of Flowering, Names, and Vertues to Each Plant, Useful in Physic or Admired for Beauty: To which is Annext a Kitchin-Garden Furnished with All Manner of Herbs, Roots, and Fruits, for Meat or Sauce Used with Us, with the Art of Planting an Orchard... All Unmentioned in Former Herbals. London: Printed by R.N. and are to be sold by Richard Thrale at his shop at the signe of the Cross-Keys at S. Pauls-gate, going into Cheap-side. pp. 160–170.
Caiola, Maria Grilli; Faoro, Franco (2011). "Latent virus infections in Crocus sativus and Crocus cartwrightianus".Phytopathologia Mediterranea.50 (2):175–182.JSTOR26458691.
Challenger, Charlie (March 1986)."The Pleasures of Crocus".The New Zealand Garden Journal (Journal of the Royal New Zealand Institute of Horticulture).1 (1):12–17.
Kandeler, R.; Ullrich, W. R. (25 November 2008). "Symbolism of plants: examples of European-Mediterranean culture presented with biology and history of art: JANUARY: Crocus".Journal of Experimental Botany.60 (1):6–8.doi:10.1093/jxb/ern360.PMID19213723.
Mohtashami, Leila; Amiri, Mohammad Sadegh; Ramezani, Mahin; Emami, Seyed Ahmad; Simal-Gandara, Jesus (November 2021). "The genus Crocus L.: A review of ethnobotanical uses, phytochemistry and pharmacology".Industrial Crops and Products.171 113923.doi:10.1016/j.indcrop.2021.113923.
Aghighiravan, Fatemeh; Shokrpour, Majid; Nazeri, Vahideh; Naghavi, Mohammad Reza (July 2019). "Phylogenetic Assessment of Some Species of Crocus Genus Using DNA Barcoding".Journal of Genetic Resources.5 (2).doi:10.22080/jgr.2019.2408.
Harpke, Dörte; Kerndorff, Helmut; Pasche, Erich; Peruzzi, Lorenzi (11 May 2016). "Neotypification of the name Crocus biflorus Mill. (Iridaceae) and its consequences in the taxonomy of the genus".Phytotaxa.260 (2):131–143.doi:10.11646/phytotaxa.260.2.3.
Peruzzi, Lorenzo; Carta, Angelino; Garbari, Fabio (22 October 2013). "Lectotypification of the name Crocus sativus var. vernus L. (Iridaceae) and its consequences within Crocus ser. Verni".Taxon.62 (5):1037–1040.doi:10.12705/625.7.
Harpke, Dörte; Kerndorff, Helmut; Raca, Irena; Pasche, Erich (23 September 2017). "A New Serbian Endemic Species Of The Genus Crocus (Iridaceae)".Biologica Nyssana.8 (1):7–13.doi:10.5281/zenodo.962907.
Miljković, Milica; Ranđelović, Vladimir; Harpke, Dörte (9 June 2016). "A new species of Crocus (Iridaceae) from southern Albania (SW Balkan Peninsula)".Phytotaxa.265 (1):39–49.doi:10.11646/phytotaxa.265.1.3.
Raca, Irena; Harpke, Dörte; Shuka, Lulëzim; Ranđelović, Vladimir (19 October 2020). "A new species of Crocus ser. Verni (Iridaceae) with 2 n = 12 chromosomes from the Balkans".Plant Biosystems.156:36–42.doi:10.1080/11263504.2020.1829735.S2CID225006706.
"Distribution area of the genus Crocus subdivided into five different geographic regions (A-E)".Molecular Phylogenetics and Evolution (Map).66 (3): 617–627: Supplementary material. March 2013.
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