MANTHENotes on their cultivation and propagation,with particular reference to Chasmanthe bicolor.

The increasingawareness of limitedwater resources,particularly duringthe summer monthsin the Western Cape,and the need to growwaterwise indigenousspecies 'in ourgardens, must focusattention on ourwealth of winter­growing bulbousplants, most of whichare deciduous andescape summerdrought by under­ground dormancy.Chasmanthe is asmall irid genusconsisting of threewinter-growing,summer dormantspecies endemic tothe winter rainfallregion of the north­western, Western,southern and EasternCape. These are thelow-growingChasmantheaethiopica, themedium-sizedC. bicolor, and therobust, tall-growingC. floribunda.

Chasmanthe aethiopicagrowing wild in theCape Peninsula'sSilvermine Nature Reserve.Photo: G. Duncan.

Plants of Chasmanthe, probablyC. jloribunda, were cultivated inEurope as far back as the early

1630s, and this species is recorded ashaving been in flower in Paris in1633, and was illustrated anddescribed there for the first time in1635. Often considered too 'common'to grow by gardeners in South Africa,Chasmanthe is an excellent choice fora variety of gardens in frost-free areasincluding difficult, seaside gardens

108

where it tolerates wind, sandy soil,minimal winter watering and summerdrought, as well as lightly shadedgardens with loam soils and heavywinter rainfall, or even hot and dryinland gardens in full sun. They allproduce narrow, curved flowers witharching stamens, and long, sword­shaped leaves. The generic name isderived from chasme and anthe,which refers to the gaping mouth, andthe flower, respectively.

Chasmanthe aethiopicaCommonly known as 'suurkanolpypie',this is a relatively low-growing,gregarious plant 25-70 em high withthe widest distribution of the threespecies of Chasmanthe. It occurs in avariety of habitats including acid sandand heavy clay mainly in coastal areasfrom the western part of the south­western Cape, to the southern Capeand south-eastern part of the EasternCape. The corm is slightly conical and

Veld Er Flora September 2001

Chasmanthe floribunda var. duekittii is just as easy to grow asthe more common orange form (see cover). Photo: G. Duncan.

Chasmanthe bieolor, unlike the other two species, is extremelyrare and possibly extinct in its natural habitat in the districts ofRobertson, Caledon and Franschhoek in the south-western Cape.Pholo: G. Duncan.

somewhat flattened, surrounded byseveral layers of fibrous corm tunics,and grows up to 45 mm in diameter.

It is the earliest species to flower,from late April to June, sometimes toJuly or August, and occurs naturallyon the Kirstenbosch estate, where it isfrequently encountered in semi-shade,growing on moist sandstone in largecolonies. Its flowers are arrangedalternately on the upper side of thepeduncle, and the inflorescence isunbranched. In addition to its strikingdark reddish-orange flowers and erect,somewhat fleshy bright green leaves,its ripe capsules are particularlyattractive when they split open andreveal their large, bright orange seeds.

Chasmanthe j/oribundaCommonly known as 'suurkanol' and'Adam's rib', this is probably the mostwell known Chasmanthe species. It isa robust plant growing up to 1.5 mhigh with long, broad, erect, soft­textured leaves, produced in a narrowfan-like position. The horizontalarrangement of the up to fortyelongated individual flowers on bothsides of the peduncle has given rise tothe very descriptive Afrikaans collo­quial name of 'Adam's rib', alluding toa human ribcage! It is most frequentlyseen in acidic, humus-rich soilbetween cracks of granite outcrops in

Veld &- Flora September 2001

the western and south-western partsof the Western Cape, but it also occursinland on sandstone in montanehabitats in the western part of theNorthern Cape. It has a large, flattenedcorm up to 100 mm in diameter,which is surrounded by several layersof tmlgh corm tunics. Its distributionis mainly coastal, and its floweringperiod extends from mid-July untilmid-September.

There are two colour varieties, themost common of the two being thereddish-orange variation Chasmanthefloribunda var. floribunda. The muchless frequently seen primrose-yellowform known as Chasmanthe flori­bunda var. duckittii is restricted tojust a few localities near Darling inthe south-western Cape. It flowersslightly earlier than the orange formand both produce branched inflores­cences and brownish-orange seeds.

Chasmanthe bie%rThis is a medium-sized plant growingfrom 70 cm to 1.3 metres high, butunlike the other two species, isextremely rare and possibly extinct inits natural habitat in the districts ofRobertson, Caledon and Franschhoekin the south-western Cape. The cormis slightly conical and somewhatflattened, surrounded with severallayers of dark brown corm tunics, and

grows up to 45 mm in diameter. Itsflowers are arranged alternately onboth sides of the peduncle and itsdark green, soft-textured leaves areproduced in a narrow fan-likeposition, and closely resemble thoseof C. floribunda, but are shorter andmuch narrower.

It blooms from July to earlySeptember and the highly ornamental,dark red flowers are marked withyellow and bright green, and arecurved to a much greater degree thanin C. aethiopica and C. floribunda. Itis a particularly floriferous plant andunlike the other two species, eachmature corm flowers every year, andthe flowers are longer-lasting than theother two species. During the budstage, the top of the inflorescence isconspicuously bent downwards, butstraightens out during the floweringperiod. The inflorescence is usuallyunbranched but may occasionallydevelop small branches at its base.Copious amounts of small darkreddish-maroon seeds are produced.

PollinationThe long curved perianth of theChasmanthe flower is an excellentexample of how certain southernAfrican bulbous species with large,brightly coloured flowers haveensured their survival by adapting to

109

Chasmanthe bicolor, inexplicably neglected by gardeners, isideally suited to garden and container cultivation. Photo: G. Duncan.

pollination by sunbirds. TheChasmanthe perianth tube is verynarrow at its base, but widensabruptly to form a broader cylindricaltube above, and has one or moreshallow or deep pouches at the pointof widening, which contain nectar.The long, curved beak of the lesserdouble-collared sunbird, themalachite sunbird and the orange­breasted sunbird (the three mainpollinators of Chasmanthe) whichthey insert into the perianth tube andprobe the pouches for nectar, perfectlymatch the curved shape of theChasmanthe flower. The sturdypeduncle provides a suitable perch forthe bird to cling to while feeding, andin the process of inserting its beakinto the perianth tube, pollen from thearching stamens above is depositedonto the forehead of the bird. Whenthe bird visits the flowers on anotherplant, pollen from its forehead rubsoff onto the branched stigma above,and fertilization takes place.

Another avian vi.sitor to the flowersof Chasmsanthe is the Cape white­eye, a small olive-green bird withconspicuous white rims around theeyes, which lives in flocks and is verycommon in suburban gardens in thewestern, southern and Eastern Cape.These cunning little birds, with aliking for nectar but whose beaks are

far too short andstraight to reachthe nectar byapproaching theflower from thefront, have beenseen to pierce thelower sides ofChasmanthebicolor perianthtubes in theKirstenbosch bulbnursery, thusgaining access tothe nectar.

CultivationFor frost-freeareas, few winter­growing cormousplants are astrouble-free andeasy to grow asChasmanthe. Allthree species arerecommended forgarden cuIti­vation, andC. bicolor alsodoes well as acontainer plant.e. floribundaprefers a full sunposition and thesmallere. aethiopiea andC. bieolor areideal candidatesfor difficult, semi­shaded parts ofthe garden, but

are equally successful when grown infull sun. All three species will growand flower in even the poorest of soilsbut to achieve excellent flowering, arich, well-drained soil is recom­mended and large quantities of fullydecomposed compost and a fewhandfuls of tlonemeal should beworked into very sandy soils. Whengrown in the open garden,Chasmanthe species should be leftundisturbed for three to four years, sothorough preparation of the soil isrequired to ensure good flowering.

The large flat, pancake-like cormsof e. floribunda should be plantedabout 20 cm apart, with about 5 cm ofsoil over the top of the corm toprevent them from falling over instrong wind. The much smaller cormsof e. bieolor and e. aethiopiea can beplanted 10 cm apart, and 2-3 cm deep.Like all deciduous, winter-growingcormous plants, the corms ofChasmanthe are stimulated into activegrowth after their long summerdormancy by cooler night tempera­tures in late summer and earlyautumn. Active growth is indicatedfirst by the development of new roots,followed shortly afterwards by leafshoots. Chasmanthe corms are soresilient that hardly any artificialwatering is necessary in the winterrainfall region of South Africa, but in

frost-free parts of summer-rainfallareas, a thorough watering once perfortnight is necessary throughout thewinter-growing period, up until earlyspring. No supplementary liquidfeeding is necessary during thegrowing period, but the addition ofslow-release granular fertilizer such asOsmocote or Horticote is beneficial.

As temperatures rise towards earlysummer, the corms begin to enterdormancy, indicated by a browning ofthe leaves, which should be cut backto just above ground level when fullydesiccated. Although Chasmantheprefers a completely dry dormantperiod during the summer, the cormsare tough enough to withstandsummer rainfall or irrigation,provided that the soil drains freely.As far as I'm aware, Chasmanthecorms are not frequently taken bymole rats under cultivation, butporcupines will certainly eat them inplace of their favourite meal ofZantedesehia aethiopica rootstockswhen the latter is not available.

The earliest species to bloom is thedeep reddish-orange Chasmantheaethiopica, which has a very longflowering period extending from lateApril until the end of July, dependingon the wild origin of the clone beingcultivated. This species forms largecolonies if left to its own devices, butinterestingly, only about fifty percentof the mature corms in a large colonywill flower in any given season. It isnot yet known why this is, but it isevident in their natural habitat as wellas under cultivation.

Chasmanthe aethiopiea is a partic­ularly useful species for difficult,semi-shaded parts of the garden aswell as for sunny rockery pockets, anddoes equally well in clay or sandysoils. In rockery pockets, this speciescan be effectively interplanted withspring-flowering bulbous species likeBabiana angustifoiia, Ixia maeulataand Watsonia laccata.

The ubiquitous Chasmanthefloribunda is a spectacular plant, seento best advantage massed together inlarge beds, and is successfully grownat Kirstenbosch interplanted withdeciduous or evergreen, summer­flowering Agapanthus species like thedeep violet Agapanthus inapertussubsp. pendulus 'Graskop' and thepale greyish-white A. praecox subsp.minimus 'Storms River'. It can also beused as a backdrop planting to a wideherbaceous border, and is particularlyeffective in such positions when inter­planted with the tall-growing winter­flowering forms of Kniphofia uvaria.Chasmanthe floribunda var. duekittii,the bright primrose-yellow form, isjust as easily grown as the orange one,and both flower best when grown infull sun. However, like C. aethiopica,mature plants of this species do notflower every single year, so that alarge number of corms are required inorder to create a really good flowering

110 Veld &- Flora September 2001

PROPAGATION OF CHASMANTHE

effect. Trials in the Netherlands arecurrently being conducted withC. floribunda var. duckittii todetermine exactly which factorsinfluence flower formation, in order tomake this plant a commercially viableflower bulb crop. C. floribunda is thetoughest of the three species, andeasily survives garden irrigationduring its summer dormant period.

The much less well-knownChasmanthe bicolor has for too longbeen neglected by-gardeners, and inmy view it is the most desirable of thethree species. Its most importantattribute is that mature corms flowerreliably every single year, unlike thoseof C. aethiopica and C. floribunda. Itcan be grown equally successfully inboth partial shade or full sun, and theplant produces copious amounts of

Chasmanthe is one of the easiestirids to propagate, either by seed

or by offsets. The hard, rounded seedsare about the size of a small pea, andare ready to be harvested once thecapsules have started to turn palebrown and split open, revealing thebright to dull orange or reddish­maroon seeds, which should be storedfor the summer before sowing inautumn. Seeds can be kept at roomtemperature for up to a year, or in thevegetable compartment of a fridge ifthe seeds are to be stored for sowing inseveral years time. Sow the seeds inautumn (mid-April to May in theSouthern Hemisphere) after coolweather has definitely set in, at adepth of 3-5 mni, in deep seedtrays,pots or seedbeds, filled with a well­drained medium (equal parts of river­sand or silica sand and finely siftedcompost). Choose a position in lightshade, and keep moist by thoroughlywatering with a fine rose every two tothree days. Fresh seed germinatesreadily within three to four weeks, butbe sure to scatter the seed evenly andthinly, as sowing too thickly causesseedlings to 'bunch' together andfavours the development of damping­off fungi like Pythium, especially afterwatering. It is always preferable towater seedlings of bulbous speciesduring the morning, as this allowsthem to dry off during the rest of theday, leaving the leaves dry at night andredllcing the risk of attack bydamping-off fungi. The seeds can alsobe dusted with a fungicide like Thiramor Thiulin prior to sowing. Underideal conditions, C. aethiopica andC. bicolor can be brought to floweringstage during their second season ofgrowth, but C. floribunda usuallyflowers in its third year from seed.

All three Chasmanthe speciesreadily develop offsets (daughtercorms) produced from axillary buds

Veld &' Flora September 2001

seed, as well as forming offsets anddivision of the mother corm. The darkred and yellow flowers have strikingbright green markings that are idealfor mass planting towards the middleof a herbaceous border. Its free­flowering nature makes it suitable forcultivation in deep containers with adiameter of 30 or 35 cm. Pottedflowering specimens will remain inflower for up to three or four weeks ifkept well watered. Its corms are notquite as resilient to garden irrigationduring its summer dormant time asthe other two species, and are bestplanted in an area not heavilyirrigated during the summer.

A word of caution to bulb enthu­siasts in Australia - the genusChasmanthe thrives in that country,and it could be potentially invasive,

on the mother corm, andto a lesser extent, alsopropagate by division ofthe mother corm. C. flori­bunda also occasionallypropagates by theformation of horizontalstolons which develop intonew corms at their tips.A mature corm can produceup to five daughter cormsper growing season, so thatafter four years ofremaining in the sameposition, a large clump ofcorms will have formed.Large clumps ofChasmanthe need to belifted and divided everythree to four years as theclumps become too thickand flowering performancetends to diminish markedlywith C. aethiopica andC. floribunda. The dormantcorms can be lifted at anytime during the summer orearly autumn months, upuntil the middle of Marchin the Southern Hemi­sphere. Use a large garden fork to liftthe clumps, then separate the offsets,remove and discard the 'stacks' of oldcorms which have remained under­neath the newest mature corm, andeither replant the corms or store themin a cool dry place until planting time.Be sure to dust loose corms during thestorage period with Bexadust todiscourage the development of mealybugs that thrive in the enclosedatmosphere of storage racks or paperpackets.

In general, Chasmanthe is pest anddisease free during the growing periodwith the possible occasional attack byaphids to the flower buds, which areusually made short work of by Capewhite-eyes.

that's if this has not alreadyhappened! A garden hybrid belongingto the closely related genusCrocosmia, known as Crocosmia xcrocosmiiflora (previously widelyknown as Montbretia) has alreadyescaped and established itself inAustralia and in many othercountries, including Bolivia andBrasil, where it is now firmly estab­lished along cloud forest verges. ®

Further readingDe Vos, M.P. 1985. Revision of the South

African genus Chasmanthe (Iridaceae).South African Journal of Botany 51(4).252-261.

Duncan, G.D. 1989. Chasmanthe. In: DuPlessis, N. & Duncan, G.D., Bulbous plantsof southern Africa. Tafelberg, Cape Town.

Chasmanthe floribunda. Photo: G. Duncan.

SOURCES OF SUPPLYCorms and seeds of Chasmanthe

are seldom available fromcommercial nurseries or

specialist bulb nurseries in SouthAfrica, but seeds of all three

species, including Chasmanthefloribunda var.duckittii areregularly available from theKirstenbosch seed catalogue,either free to members of theBotanical Society, or for sale

when stocks are available. Cormsof Chasmanthe are periodically

available at the BotanicalSociety's annual Garden Fair.

111