scentsational freesias

7/31/2019 Scentsational Freesias

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For city dwellers around the world, the appearance of freesias inflorists shops and in the barrows of flower sellers on street cornersis the urban equivalent of the unfurling of spring wildflowersin fields and woodlands. Unlike many of their rural cousins, however,freesias pour forth a strong, sweet fragrance from their trumpet-shapedflowers, sounding a brilliant olfactory fanfare to dispel the drearynorthern winter. Their bright sprays of blossom burst onto streets withthe lan of a cancan chorus line, the ruffled flowers dancing down eachstem in a perfectly choreographed row, petals swirling around dainty,creamy stamens vivacious and irresistible as the grisettes of Maxims.

Modern freesia cultivars, puffed up by polyploidy, are essentially theproduct of the ingenuity and application of late-Victorian and Edwardianbreeders in Europe. The wild species from which their stocks wereoriginally drawn are endemic to the south-western Cape but are barelyknown, even in their native land.

Botanists today recognize 16 species of Freesia, one of them sorecently recognized that it has yet to be formally named. All but four of

the known wild species are endemic to Namaqualand and the south-western Cape, with the greatest concentration in the Worcester-LittleKaroo and adjacent littoral, in the Overberg and the southern Cape.Known colloquially as flissies from their flask-shaped flowers arrangedin perky, arched spikes, most species exude a heady, violet-like fragranceduring the day.

Tentative beginnings The first freesias found their way to Europe in the mid SeventeenthCentury at a time of rising interest in Cape plants. Bulbs and succulentswere among the plants that most readily survived the rigours of thelong sea voyages from the Cape to the ports of Europe, and the firsttwo Freesia species known to science were described from plants thathad been established in cultivation in The Netherlands some timeprior to 1768. They were given names that alluded to some notablecharacteristic, aptly in one case the striking fragrance for which thegenus would later become famous. In naming F. caryophyllacea , theCarnation-scented Freesia, however, the Dutch botanist Nicolaas Burmanreveals a deplorable knowledge of bouquet since no species of Freesia produces oil of cloves, the primary component of the smell of wildcarnations. In keeping with botanical conventions of his day, Burmanplaced his two new species in the genus Gladiolus on account of theirtwo-lipped, trumpet-shaped flowers.

Freesia itself was only established as a separate genus a century later,

in 1866, by the German botanist, F.W. Klatt, who is honoured in anotherbotanical curiosity from the Cape, the shrubby iris Klattia. At this time thename Freesia was applied only to those species with the characteristicfunnel-shaped flowers that are familiar to us from the cultivated forms,but three decades later Klatt expanded his conception of the genus toinclude a few species with narrowly tubular, mostly unscented flowers,

Scentsational freesiasChemical analysis of the fragrance of freesias s pports the division of the gen sFreesia into two gro psbased on DNA and bract text reby John ManningandRoman Kaiser

Both the typical yellow form of Freesia leichtlinii (Dune Freesia) and the white form (previously known asFreesia alba) are important in the origin of modern freesia cultivars.


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the texture of the floral bracts that had first been pointed out by Brownin 1935. On the one hand we have those species with firm-textured,green bracts, and on the other those with thinner, more membranous oreven papery bracts. Both groups are dominated by species with funnel-shaped flowers but each also contains one or more tubular-floweredspecies. This coincidence between DNA and bract type is reflected in ourdecision to recognize these two groups as subgenera.

A cultivated past The history of modern freesia cultivars goes back to the late NineteenthCentury, with the introduction into cultivation of yellow- and white-flowered forms of F. leichtlinii (the latter under the name F. alba ).Selection from this material gave a range of white and yellow formsthat enjoyed some popularity but it was the introduction of pink- anddeep yellow-flowered forms of F. corymbosa (known respectively as F.armstrongii and F. aurea ) in the closing years of the century that providedthe real stimulus to freesia breeding. By the end of the first decade of the Twentieth Century the Dutch nursery firm of Van Tubergen hadproduced a range of tall freesias in a variety of colours including blue,mauve, shades of rose, yellow and white, and the first polyploid, Freesia Buttercup, made its appearance in 1911. Today most registered cultivarsare polyploid, with diploid strains important mainly in areas where plantsare grown every season from seed.

Breeding of Freesia continues today with the resultant varieties,including double-flowered types, bearing less and less resemblance tothe wild species from which their stock originally stemmed. The cultivarsrange from 1030 cm in height, in habit from neat and tufted to tall and

graceful, in inflorescence from short and semi-erect to long, sparselybranched and horizontal, and producing scarcely to strongly fragrantflowers in almost every conceivable colour. Almost shockingly, however,no additional genotypes appear to have been introduced into the mixsince those first crosses were made in the late Nineteenth Century, andall commercial freesias are essentially derived from repeated crossings of

colour forms of just two wild species, F. corymbosa and F. leichtlinii . This isan almost incredible neglect of the potential that exists among the wild

species for the addition of new flower shapes and other characteristics.Although freesias are famous for their fragrant flowers, typically butinadequately described in horticultural literature as sweet-smelling, veryfew cultivars have been developed primarily for their fragrance. Indeed,many commercial varieties have lost their scent during the breedingand selection processes, a cause for special concern among Chinese andJapanese growers. The favoured colours by far in both Holland and Japanare yellow, followed by white, and it is probably no coincidence thatthese colours are typically the most fragrant.

Scenting success The division of Freesia into two groups based on DNA and bract texturehas received spectacular support from our chemical analysis of floralfragrance in the genus. The scent in freesia flowers emanates primarilyfrom the bright yellow or orange patches that decorate the lower lip of the flowers like smears of turmeric. Scented members of the group withdelicate bracts, such as F. corymbosa , produce floral fragrances dominatedeither by the chemicals linalool (which has an attractive floral-woodysmell) or nerol (fresh and rose-like with citrus undertones). Members of the group with leathery bracts, which includes F. caryophyllacea and F.leichtlini , are chemically more diverse, with scents that are dominatedby nerol or -terpineol (sweet-floral with pine-needle undertones) butwith the signal addition of the chemicals -ionone and dihydro--ionone(green-woody, fruity and very floral with a distinct freesia smell). Theionones, which are extremely potent with very low odour thresholds to

the human nose, have found an enormous appreciation in perfumeryduring the past three decades and many of the famous fragrancescontain high amounts of them, often in ratios similar to those found innature. Relatively widespread among flowering plants, ionones have thecurious characteristic that they are invisible to around 10% of humanswho are unable to detect their odour through a genetic peculiarity. As

Gas chromatograms of selectedFreesiaspecies and cultivars. Individual peaks represent different chemical compounds, and the size of each peak is proportional to the relative concenchemical.A The scent of F. leichtlinii is characterized by the presence, among other compounds, of high concentrations of -terpineol and -ionone as well as smaller amounts of three otchemicals (Dihydro--ionone, 2-methylbutyraldoxime (E+Z) and -selinene), all highlighted in red. These particular compounds are absent from the scent of F. corymbosa, which is recognizable bythe presence of trace amounts of four unusual chemicals derived from the more common, dominant constituent, linalool (2-methyl-2-vinyltetrahydrofuran-5-ol, 2,6-dimethyloctand 2,6-dimethylocta-1,7-dien-3,6-diol), all highlighted in blue.B White-flowered commercialFreesiacultivars betray their mixed parentage by combining the diagnostic fragrance markers of bothF. leichtlini (highlighted in red) and especiallyF. corymbosa(highlighted in blue), whereas yellow-flowered cultivars approach pureFreesia leichtlinii in their fragrance.

A. K6961830m CP-Wax 52CB, 1.2l on columnRT: 2.30 - 50.00 Freesia x hybrida yellow,18.4.09, 11.00-14.00

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Freesia x hybrida white, 18.7.06, 9.40-13.4030m CP-Wax 52CB, 1ul on column

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Freesia leichtlinii, Kirstenbosch, 28.7.05, 9.00-15.0030m CP-Wax 52CB,1l on columnRT: 2.30 - 50.00

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K63055Freesia corymbosa "armstrongii", 27.9.07, 11.00-16.0030m CP-Wax 52CB, 2 l on column

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t h y l o c t a - 1 , 7

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- d i o l

OOH

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B.


4/4SEPTEMBER 200 9 | VELD&FLORA 135

TOP:Freesia fucata, a rare species from near Villiersdorp, has the highly fragrant, funnel-shaped flowers that are characteristigenus. The scent in freesia flowers emanates primarily from the bright yellow patches that decorate the lower lip of the flsmears of turmeric.ABOVE: TrueFreesia refractawas never used in the breeding of freesia cult ivars and references to it in the early horticultural liteactually apply toF. corymbosaandF. leichtlinii . Photos: J. Manning.

a result, people who cannot smell ionones willperceive the scent of flowers containing thesechemicals in their fragrance spectrum quitedifferently from those fortunate enough tohave active ionone receptors.

A new beginningOur identification of ionone-negative andionone-positive groups in the genus raisesthe exciting possibly of developing distinctfragrance-lineages in Freesia. The very earlycrossing of F. leichtlinii with F. corymbosaeffectively removed this potential from currentbreeding programmes by unwittingly blendingthe two fragrance-groups.

The new understanding of relationshipsamong the species that was provided byDNA analysis opens up the opportunity forselective breeding within each of the twofragrance-groups to derive fragrance-cultivarsthat can only enhance our enjoyment of this

wonderful genus.It is most unfortunate, for instance, that true

F. refracta has never figured in the parentageof commercial cultivars as it has a rich, rose-like scent stemming from the chemicals nerol,geraniol and citronellol. These rosy-floral andcitrus-related scent constituents harmonizeexquisitely with the fragrance of the existingcultivars. Another great mystery is why F.caryophyllacea , an attractive and relativelycommon species that was among the very firstto be grown in Europe, has never been involvedin breeding programmes. It offers ravishingrosy-floral fragrance notes via geraniol andnerol and their derivatives.

Floral scents, elusive and evocative, add afinal touch of glamour to the beauty of manyof our wildflowers but they are a sadly under-appreciated feature that richly rewards closerattention.

THE AuTHORSDr John Manning is a Senior Specialist Scientist at theCompton Herbarium, South African National BiodiversityInstitute, Kirstenbosch. Dr Roman Kaiser is a chemistat the Givaudan fragrances and flavours company inSwitzerland.

WHAT DOES THAT MEAN?

Diploid Two of each type of chromosomeGenotype The genetic make-up of anorganism as opposed to its physicalcharacteristics

Littoral Of or on the seashoreMorphological Shape and form orphysical characteristics of an organismPolyploidy Having more than theusual number of chromosomes

scentsational freesias

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