Know and grow indigenous bulbs

Spectacular, rewarding triton

Tritonia crocata. Photo: Graham Duncan.

132 September 2006 Veld&Flora

by Graham Duncan, Kirstenbosch

From coastal roadsides of the south­

ern Cape to high altitude slopes of

the Kwazulu-Natal Drakensberg, themainly spring and summer-flower­

ing iridaceous genus Tritonia contains

about twenty-seven species of decidu­

ous, cormous plants. They are encoun­

tered in all provinces of South Africa as

well as in Lesotho and Swaziland, and

their distribution extends northwards

almost to the equator in Tanzania in

Central East Africa. Tritonia was stud­

ied in detail by Dr Miriam P. de Vos in

the early 1980s and her excellent final

account of the genus appeared in the

Flora of southern Africa, in 1999. The

genus is concentrated in the south­

ern Cape and most of the species are

adapted to winter rainfall conditions,

flowering taking place mainly in spring

and early summer. The summer-grow­

ers flower mainly from midsummer to

autumn. They occur in greatly differing

habitats, from arid rocky slopes of the

southern Richtersveld to high rainfall

parts of the northern Drakensberg.

Flower shape varies from regular to

strongly zygomorphic (see glossary on

p. 134), with flower colour predominat­

ing in shades of orange.

Two species (Tritonia crocata and

T. squalida) are particularly showy in

having curious translucent zones or

'windows' along the margins of their

tepals. In a number of others, promi­

nent yellow, erect, peg-like protuber­

ances emerge from the lower tepals

and are thought to function in reducing

the space in the throat of the perianth,

thus ensuring that the back of a visiting

insect will brush against the anthers

and stigma and ensure pollination, as

in T. watermeyeri. The attractive fan­

like foliage varies from bright green with

flat margins to grey and spirally twisted

with heavily wavy margins. The genus

Tritonia was brought into being by the

English botanist J. B. Ker-Gawler in

1802, who named it for the Latin word

triton, a weathervane, for the vari­

able orientation of the stamens in some

species.

Tritonias or 'kalkoentjies' as some

species are locally known, have been

grown in Europe and England sincethe latter part of the eighteenth centuryand the colourful spring and early sum­mer-flowering hybrids commonly growntoday in gardens and window-boxes intemperate regions, and in greenhousesin colder parts, are derived from mainlytwo species: the orange-flowered T. cro­cata and the pink-flowered T. squalida,both of which emanate from the south­ern Cape. Although easily cultivated,the hybrids seldom outshine the truespecies in beauty, and with a soundknowledge of their cultivation require­ments, a number of Tritonia species canbe grown very successfully.

CultivationIdeal conditions for the successful cul­tivation of Tritonia species include asunny, well-ventilated aspect, a sharply­drained growing medium, heavy drench­ing at regular intervals during the grow­ing season, and maintenance of a dryperiod during dormancy. Although con­siderable variation exists in the depthat which the corms of Tritonia speciesoccur in the wild, ranging from shallowto relatively deep-seated, under cultiva­tion the corms of all species need onlybe planted at roughly twice the heightof the corm, or with about 2 cm ofgrowing medium above the corm for thesmaller species like T. crocata and T.watermeyeri, or about 4 cm above forlarger species like T. disticha and T. lin­eata. The corms of the winter-growersare planted in autumn (March to April)and for the summer-growers in spring(August to September) in the SouthernHemisphere. Once planted they shouldbe watered heavily and then not againuntil the leaf shoots appear, after whicha heavy drench roughly once per weekis suggested for most species. Wateringof arid habitat species like T. karooicaand T. watermeyeri requires a measureof restraint and the frequency of water­ing for these should be delayed to per­haps once every ten days to two weeks,when the soil moisture has reacheda much lower level. An ideal growingmedium for most tritonias is one partriver sand, one part loam and one partfmely sifted compost or finely milledbark. For arid habitat species the riversand component should be increased totwo parts, and the loam component dis­pensed with entirely. The arid habitattritonias require higher light intensitythan most others for successful flower­ing, but generally an aspect receivingmorning sun and afternoon shade, orbright light for as much of the day as

possible, is necessary. Applications oforganic fertilizer such as Kelpak 66are beneficial to all tritonias at three­weekly intervals during the growingperiod, or alternatively Neutrog BounceBack pellets can be applied to the soilsurface as a slow-release fertilizer. Afterflowering, watering should be withheldas the leaves die back and seed forma­tion takes place, and the corms shouldbe allowed a completely dry summer orwinter dormant rest, depending on thespecies.

As tritonias have pronounced winter­or summer-growing cycles, it is essen­tial to ascertain their correct growthcycle if they are to be cultivated suc­cessfully. The winter-growing speciesrequire a dry summer rest while thesummer-growers must he kept com­pletely dry in winter. Some species areable to tolerate a certain level of mois­ture during their dormant period (suchas T. crocata and T. deusta) providedthat the soil medium is sufficiently. welldrained, while others from arid habitatssuch as T. karooica, and T. watermeyeriare completely intolerant of moisturereceived at the wrong time of year androt easily. All tritonias lend themselvesto cultivation in containers while onlycertain species are suited to generalgarden cultivation. The corms of aridhabitat members such as T. karoo­ica and T. watermeyeri cannot surviveexcessively moist conditions duringtheir winter growth period such as isexperienced in the southern suburbsof Cape Town, and have to be grownunder cover in these areas.

The flowers of the strongly zygomor-

RIGHT: One of the most spectacular species,Tritonia squalida multiplies rapidly bycorm offsets and has long-lasting flowers.Note the distinctive translucent zones or'windows' along the tepal margins.Photo: Graham Duncan.

The winter-growingspecies require a drysummer rest while thesummer-growers mustbe kept completely dryin winter.

phic species (such as T. watermeyen)remain fully open irrespective ofweath­er conditions, whereas those specieswith regular or almost regular flowers(such as T. crocata) close slightly dur­ing inclement weather. Owing to theease with which some Tritonia specieshybridize when grown in close proxim­ity (especially T. crocata, T. deusta and

T. squalida), it is essential to isolate andhand-pollinate specimens just prior to,and during flowering, if pure seed isrequired. Tritonias are hardy in mildparts of the Northern Hemisphere andin areas where winter temperaturesdo not remain below zero for pro­longed periods, but in cold climatesthey require the protection of the coolgreenhouse. In the wild, most winter­growing tritonias flower in late springand early summer at a time when theirleaves are in an advanced state of des­iccation, as temperatures rise and soilmoisture rapidly diminishes. In order toensure that the foliage of these speciesremains attractive and green through­out the flowering period in cultivation,it is essential that the plants be keptwell watered by drenching them thor­oughly from late winter onwards, untilflowering has taken place.

PropagationAll Tritonia species are easily propa­gated by seed, and most can also beincreased by the separation of corm off­sets and cormlets. In addition, cormelsare produced at the tips of horizontal,subterranean stolons in a few species.Large corm offsets are formed when twoor more shoots develop from the upper-

ABOVE LEFT: Tritonia deusta subsp. deustaoccurs in colonies in the southem Cape coastaldistricts from Caledon to Riversdale, and inlandto Robertson and Montagu. It flowers in latespring and early summer.

ABOVE RIGHT: A late-flowering species, theeasily grown Tritonia bakeri subsp. bakeriblooms from early to midsummer and has dis­tinctive purple anthers.

RIGHT: Tritonia crocata is one of the mostobliging species in cultivation, highly recom­mended for massed display in rock gardenpockets, spring borders and deep containers.Photos: Graham Duncan.

What does that mean?

axillary bud bud arising from a corm at thejuncture formed by a leaf or bract and cormcorm compressed, swollen subterraneanstem which is vertically orientated, renewedannually and covered by dry leaf basescormel small corm that develops at the tipof a stoloncormlets small corms that develop in a ringaround the base of amother cormoffset a short shoot that arises from an axil­lary bud near the base of a stem and givesrise to adaughter plant at its apex.perianth the sepals and petals together, par­ticularly when they are similarrhizome specialized underground stem thatgrows horizontally, producing roots and foli­age at right angles to the rhizomestolon thin, elongated stem trailing overor just under the soil surface, producing acormel at its tiptepal sepal or petal, when no distinction ismade between themzygomorphic irregular, and able to be bisect­ed into identical halves in one plane only

134 September 2006 Veld&Flora

most axillary buds on the mother corm,

while smaller cormlets develop fromlower axillary buds around the baseof mother corms. They develop during

the growing period and mature towardsthe end of the flowering season. Theycan be separated at any time duringthe corresponding dormant period and

should preferably be re-planted immedi­ately into dry soil, as the corms are fre­quently subject to mealy bug infestationif stored loose in packets or trays forlong periods. Corm offsets often flowerduring their second year while corm-

lets and cormels usually take a furtheryear. For the winter-growers, seeds are

sown in autumn once temperatureshave cooled down markedly after thehot summer, and for the summer-grow­ers, in spring, as temperatures rise.Fresh seeds germinate readily within2-4 weeks and care should be taken

to sow thinly and ensure that a well­ventilated environment is maintainedin order to reduce the incidence ofdamping-off fungi. Seeds can be sown

in deep seed trays or seedbeds in thesame medium recommended for maturecorms. The deeper the seed trays orbeds, the faster the young corms willdevelop and reach flowering stage. The

seeds are covered with 3-4 mm of sow­ing medium and should be sown in anarea receiving high light intensity, orfull morning sun and afternoon shade.

They should be kept moist by wateringthoroughly with a fine rose about twiceor three times per week, depending onweather conditions. Seedlings of easilycultivated species like T. crocata and T.

squalida will usually flower for the firsttime during their second season, whilelarger species like T. lineata and thosefrom arid habitats such as T. karoa­ica and T. watermeyeri will usuallyflower in their third year, under idealconditions.

Pests and diseases

Compared with other southern Africanirids, tritonias are moderately suscep­tible to pests and diseases. The cormsand leaf bases are subject to the univer­sal mealy bug scourge, against whicha preventative treatment of a mineral

oil drench (e.g. Oleum) can be appliedin early autumn for the winter-grow­

ers, and in early spring for the sum­mer-growers. Developing flower budsmay at times become heavily infestedwith thrips, especially in the summer­

growing species, resulting in deformedflowers. In highly susceptible areas theflower buds should be sprayed pre­

ventatively with Bio Kill garden sprayas soon as they emerge, well before thethrips have had a chance to invade.Flower buds and leaves are sometimessubject to attack by aphids, and red

spider mites are prevalent on the foliageof the broader-leafed species as tem­peratures rise in spring and throughoutsummer, resulting in leaf desiccation

and a silvery-bronze sheen, for whicha full cover spray with Oleum is recom­mended. The corms of Tritonia species

are taken by porcupines and mole rats.Jelly-like scatter crystals known in thetrade as 'Get Off My Garden' may be

effective in deterring porcupines, whilemolerats can be temporarily beaten by

planting corms in sunken wire basketsprotected on all sides.

The leaves of certain winter-growingspecies especially T. crocata, T. deus­

ta and T. squalida are susceptible toattack by unsightly rust fungi in winter,and it is essential that they be grownin well ventilated positions receiving asmuch direct sun or bright light as pos­sible. In severe infestations rust fungi

can be controlled with mancozeb (e.g.Dithane M45). All Tritonia species aresubject to fungal infection by Botrytis

which causes reddish-brown lesions

on the corms, and can be controlled bydusting corms with captab (e.g. Kaptan)prior to planting. Tritonia seedlings aresusceptible to damping-off by Pythium

fungi which is prevalent in poorly ven­

tilated conditions and when seeds havebeen sown too thickly. The seeds can bedusted with Kaptan prior to sowing.

Ten of the bestTritonia bakeri is an elegant, large­flowered species growing up to 800 mmhigh with pure white, creamy-yellowor mauvish-pink blooms with striking

violet anthers and a very long perianthtube. The subspecies bakeri (see illus­tration) has white or creamy-yellow

flowers while those of the subspecieslilacina are smaller and pale mauvish­pink. T. bakeri is a winter-grower from

the Little Karoo and Langkloof, andalso occurs in the southern Cape fromGeorge to Riversdale. It flowers late in

the season, from early to midsummerand has distinctive narrow, erect cylin­

drical leaves. It performs well in deepcontainers and although the corms arelong-lived, they are rather slow to mul­

tiply. It is easily raised from seeds sownin autumn, the seedlings usually reach­

ing flowering stage at the end of theirthird year, under ideal conditions.

Tritonia crocata (kalkoentjie) is prob­ably the best-known member in cultiva­tion and together with T. squalida wasone of the species used in the creation

of the brightly coloured hybrids widelygrown in temperate gardens throughoutthe world today. It is a variable, win-

ABOVE: Tritonia disticha subsp. rubrolucens,flowering on Mt. Thomas in the Eastern Cape, isa summer-growing, high altitude tritonia.Photo: Cameron McMaster.

RIGHT: Tritonia karooica has attractive bluish­grey leaves and requires high light intensityand a sharply drained growing medium forsuccessful flowering. Photo: Graham Duncan.

ter-growing plant and occurs in largecolonies in coastal parts of the southernCape stretching from Swellendam toGeorge and Humansdorp. It produces

an attractive fan of lance-shaped leavesand flower colour varies from shadesof bright fiery orange to deep orange­

red or pinkish-orange. The three lower

tepals have a narrow yellow or dark redcentral stripe in the throat, and all thetepals have attractive narrow translu­

cent zones or 'windows' on the margins.It is one of the most easily cultivatedtritonias, reaching up to 450 mm high,providing a brilliant, reliable displayfrom mid-spring to early summer. It

is suited to rock garden pockets and

ABOVE: The curious wavy-margined grey leaves and long-lasting blooms of Tritonia watermeyeri make it oneof the most rewarding tritonias to grow in containers. Note the three prominent yellow protrusions on thelower tepals, whose function is thought to reduce the space in the throat of the perianth, thus ensuring thatthe back of avisiting insect will brush against the anthers and stigmas, facilitating pollination.Photo: Graham Duncan.

deep containers, and multiplies rapidlyby corm offsets. It readily hybridizes

with T. deusta and T. squalida and theflowers must be isolated and hand-pol­linated in order to obtain pure seed.

Tritonia deusta (kalkoentjie) is a vari­

able, winter-growing species with largeorange-salmon to bright reddish-orangeflowers, with or without a prominentdark reddish-black marking or cen­tral stripe in the throat of the outer

136 September 2006 Veld&Flora

tepals. It occurs in the southern Capefrom Caledon to Riversdale and inlandto Robertson and Montagu. It is eas­

ily confused with T. crocata, differingmainly in the absence of translucentzones or 'windows' on the margins ofthe tepals, and in having a prominentyellow, star-shaped base within the

perianth tube. The subspecies deustahas redddish-black markings on the

outer tepals, while in the subspeciesminiata there are no markings. It pro-

duces an attractive fan of lance-shapedleaves, grows to 450 mm high in culti­vation and multiplies rapidly by corm

offsets. Flowering takes place from latespring to early summer and it is wellsuited to rock garden pockets and deepcontainers. It readily hybridizes with

T. crocata and T. squalida and flowersmust be isolated and hand-pollinated inorder to obtain pure seed.

Tritonia disticha is a summer-grower

and has a fairly wide distribution extend­ing from the south-eastern parts of theEastern Cape to KwaZulu-Natal, the

north-eastern Free State, Mpumalangaand Swaziland. It has long, narrowlylance-shaped leaves and a many-flow­

ered spike up to I m high consistingof widely funnel-shaped pink, red or

orangy-red flowers with a small yel­low marking outlined in red on thelower tepals. The subspecies distichaoccurs at lower altitude and has longer

bracts than those of subsp. rubrolucenswhich occurs at higher altitude (andis illustrated on p. 135). This specieshas a long flowering period from earlysummer to early autumn and is easilymaintained in cultivation provided thecorms are kept completely dry over the

winter dormant period, and that mealybugs are judiciously controlled.

Tritonia karooica is widely distributedthroughout the western and northernparts of the Great Karoo and is a win­

ter-growing plant up to 200 mm high

that flowers early in the season, fromearly to mid-spring. Its dark bluish-greyleaves are borne in an attractive fan,and the funnel-shaped flowers occurin shades of brownish-yellow, cream,burnt orange or salmon, with promi­

nent darker veins and bright yellowmarkings on the lower three tepals. Thetepal tips become strongly re-curvedwith age and the flowers emit a pleas­ant sweet fragrance in the evening. Theplants are very sensitive to over-water­ing and must have very bright light and

sharply drained soil in order to flowersuccessfully. Corm offsets are slow todevelop and it is best propagated fromseeds, that flower in their third season.

Tritonia laxijolia is a summer-growerwith a wide distribution extending from

the eastern parts of the Eastern Capeto the north-eastern parts of the GreatKaroo, up to the Central African coun­tries of Malawi, Zambia and Tanzania.

It grows to 600 mm high and has along flowering period extending from

early to late autumn in southern Africa,to midwinter in Central Africa. The

plants have narrow linear leaves andbear graceful lax spikes of six to fifteenbright salmon-pink to pale brick-redflowers, each of the three lower tepalshaving a bright yellow peg-like protru­

sion that extends upwards. This speciesprefers a lightly shaded position andis most suitably grown as a containersubject. The corms must be kept dry

over the winter dormant season and aclose watch should be kept for mealybug infestation, to which it is particu­larly susceptible.

Tritonia lineata (bergkatjietee) is asummer-grower and is a very commonspecies in the eastern and south-east­ern parts of the Eastern Cape, and is

also widely distributed in the easternsummer rainfall regions of South Africain KwaZulu-Natal, eastern Free State,Mpumalanga and Lesotho. It flowers

from early spring to midsummer, andis dormant during the winter months.It has cream or yellow, funnel-shapedflowers distinctly marked with brown­ish lines, narrowly lance-shaped leaves,and grows up to 850 mm high. The vari­ety lineata grows to well above 300 mm

high whereas the variety parvifolia hasshorter, narrower leaves up to 300 mmhigh. This species performs very well incultivation, multiplying rapidly by cormoffsets and by seed, and is most suit­ably grown in rock garden pockets, her­

baceous borders or deep containers.

Tritonia securigera (tritonia,kalkoentjie) is a very variable, winter­growing species and occurs in the Little

Karoo, the eastern parts of the GreatKaroo and in the southern Cape fromMossel Bay to Humansdorp. lt haslance-shaped, somewhat rigid foliageand attractive sprays of reddish-orange

blooms with yellow throats, each of thethree lower tepals with a prominentpeg-like protrusion arising from thebase. It flowers from late spring to early

summer and the plants can grow up to350 mm high under ideal conditions.The corms multiply rapidly by offset

formation and an abundance of seedis set in cultivation following hand pol­lination. lt is well suited to rock garden

pockets and deep containers.

Tritonia squalida (Mosselbaai­kalkoentjie, kalkoentjie) has been sad­dled with a grossly inappropriate spe­cific name as it ranks as one of the

most beautiful of all the tritonias. In

herbarium specimens, the flower colourfades to a dirty brownish-mauve colour,hence the species name given by anunsuspecting botanist in the late eight­

eenth century, who evidently had neverseen it in the living state. Endemic to asmall area of the southern Cape fromAlbertinia to Stilbaai, it is a winter­grower and closely resembles T. crocatain flower and leaf shape, differing main­ly in the distinctive deep mauvish-pinkto pale pink colouring of the flowers,with prominent deeper pink veins inthe tepals, and in the absence of a nar­

row, yellow central stripe in the throatin the three lower tepals. An especiallyattractive feature of the flowers is thewide translucent zones or 'windows' on

the margins of the tepals. Growing upto 450 mm high, it is one of the mostdesirable and easily cultivated tritoniasand multiplies rapidly by corm offsets.It flowers in late spring and is suited to

cultivation in deep containers and rockgarden pockets in temperate climates.It readily hybridizes with T. crocata andT. deusta and the flowers need to beisolated and hand-pollinated in order to

obtain pure seed.

Tritonia watermeyeri is a winter­growing dwarf species with a very lim­ited distribution in the Little Karoo eastof Montagu. Its distinctive grey leavesare as interesting as the flowers and

have strongly wavy margins that aresometimes spirally twisted. The showy

spike is borne on a wiry dark brownpeduncle and bears 3-7 burnt orange,slightly fragrant flowers with a red­

edged yellow zone in the throat. Three

The authorGraham Duncan, horticulturist and 'bulbexpert' from Kirstenbosch, graduated cumlaude from the University of KwaZulu-Natalin April last year with an M.Sc. in Botany.The title of his dissertation was 'Charactervariation and a cladistic analysis of thegenus Lachenalia.' He is the author ofnumerous books and articles and alsoa past winner of the BotSoc's SchelpeAward for the best horticultural article inVeld &Flora.

prominent bright yellow, narrow peg­like protrusions extend upwards from

the lower tepals. It performs extremelywell in cultivation provided the cormsare kept completely dry over the sum­mer dormant period, and it is most con­veniently grown as a container subject

in a sharply drained mix of coarse riversand and silica sand, with the addition

of a little finely sifted compost. Plantheight varies from 100-300 mm and itflowers from early to mid-spring.

Sources of supply

Seeds of several Tritonia species arelisted from time to time in the annualKirstenbosch seed catalogue, issuedfree to South African members of theBotanical Society of South Africa, or

for sale when stocks are large enough.Seeds of certain species, including T.bakeri, T. watermeyeri and T. karooicaare not yet easily obtainable. Tritoniacorms are seldom available from special­ist bulb nurseries but can be purchasedperiodically at the Botanical Society'sannual Garden Fair and at the Centrefor Home Gardening at Kirstenbosch.~

Further readingDe Vos, M. P 1999. Tritonia. In: De Vos, M.P and Goldblatt, P, Flora of southern Africa7(2), 89-128.Du Plessis, N. M. and Duncan, G. D. 1989.Bulbous plants of southern Africa, pp. 132­134. Tafelberg, Cape Town.Jeppe, B. J. and Duncan, G. D. 1989. Springand winter flowering bulbs of the Cape, pp.62-65. Oxford University Press, Cape Town.

The author, Graham Duncan.

September 2006 Veld&Flora 137