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Another magnificent Costus in blossom!

September 29, 2010

Snow-white flowers and velvety leaves, these are some characteristics of the Asian Costus. These tropical plants are closely related to the gingers. Gingers (Zingiberaceae) have leaves arranged in two rows, while Costus (Costaceae) have spirally arranged leaves. In 2006, botanists used DNA analyses to show  that the genus Costus has many different origins, so a division into five genera was made, something that does make sense. The Asian Costus should thus be named Cheilocostus.

Here in Chiang Mai we have both C. speciosus and C. lacerus. Both of them may grow together, and identification based on the key characters of Flora of Thailand is difficult. They seem to be variable species, and to my experience the spiral curving of the stems may occur in both species, especially when young. Also the velvety hairs on the leaf undersides may occur in both species. Yet, at Dokmai Garden they both appear very different at sight:

Cheilocostus speciosus: elongated leaves (5-6 cm broad, one third of length), calyx and bracts pink, flower falls off after blossom which makes the cone-like inflorescence look ‘clean’, blossom begins later than in C. speciosus, corolla lobes pink (or white).

Cheilocostus lacerus: roundish leaves (8-9 cm broad, half of length), calyx and bracts vinaceous red, flower remains after blossom as a black dried tissue which makes the cone-like inflorescence look ‘untidy’, blossom begins in late August, corolla lobes white.

At Dokmai Garden we have both species, and both are in blossom right now. The white ‘flower’ is actually two fused stamens, named ‘labellum’. The three petals are just backstage workers, shielding the labellum when budding.

Being native to Dokmai Garden and Chiang Mai, these two species are fanatic monsoon plants, i.e. they will disappear totally in the dry season, so you can only see them now in the mid and late rainy season. If you water the dormant rhizomes during the drought, you may kill them. Therefore, leave them alone, and you shall be awarded with fantastic and generous blossom in the rainy season.

We had a Thai visitor, a real connoisseur, who walked around in our garden. Of all our 940 species, he only wanted to buy C. lacerus. Luckily, we had one specimen for sale. He was happy like a child on Christmas Eve, and he explained he would fly down to the south, only carrying this precious darling as his sole hand luggage. We feel happy when we can satisfy the dreams of plant lovers! Needless to say, the Thai Cheilocostus are rarely for sale, something we shall change!

Eric Danell

Cheilocostus speciosus has elongated leaves and a ‘tidy’ and pink ‘cone-like’ inflorescence (see background).

Cheilocostus lacerus has roundish leaves and after blossom an untidy red ‘cone-like’ inflorescence.

On internet you will see many pictures with the wrong names. Ginger specialist Tim Chapman is acknowledged for proof-reading this blog.

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6 Comments leave one →
  1. August 2, 2012 8:24 AM

    This leaves me somewhat confused as neither Smitinand nor Maxwell use the name C.lacerus. Maxwell has C.speciosus as common on Doi Suthep (but bizzarely above 650 m !! as it is common at lower elevations), and C.globulus Bl. (var. globulus) as rare.

    • August 3, 2012 11:14 AM

      Cheilocostus are confusing! Kew gardens acknowledge four species in the world: http://www.theplantlist.org/tpl/search?q=cheilocostus

      I can send you the recent (2006) paper on the phylogeny of Costaceae by Specht & stevenson where the genus Cheilocostus is presented. Flora of Thailand 9:2 treats Costaceae and the four Thai species (under the name Costus). C. globosus and C. dhaninivatii both have their inflorescence on a separate shoot without green leaves. C. lacerus should have straight shoots and leaves disintegrating into fibres, while C. speciosus should have more spiral shoots and leaves not disintegrating into fibres.

      Eric

  2. October 29, 2012 8:41 PM

    Just went doing a little bushcare today with a friend who has become a Costus fan and wanted to dig one up in the National Park. Restraint was observed but how can he get one for his garden?

    • October 30, 2012 6:44 AM

      He can buy straight from our garden, 200 Baht. It is becoming dormant now which is a good time for transplanting. It blooms next rainy season.

      Cheers, Eric

  3. November 1, 2012 8:14 PM

    Any suggestions about collecting seed? Many Costus are still in flower but have they been doing this for 6 months like some other Zingiberaceae? And should this mean there is seed around?
    Then if we get seed how best to make it grow?

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