The following article appeared in Volume 25, No.5 of the Journal (July – September 2006)

THAI POYSEAN (Euphorbia xlomi (Rauh))

Most of us are familiar with Euphorbia milii (des Moulins), discovered in southern Madagascar and named in 1826 by Charles des Moulins in honour of Baron Pierre-Bernard Milius who at that time was the Governor of the island then known as Île Bourbon (modern-day Reunion Island, situated in the Mascarenhas Archipelago, off the east coast of Madagascar). Baron Milius was responsible for introducing this species into cultivation in France in 1821. E. milii became popularly known as the ‘Crown of Thorns’ plant because, early in its introduction to cultivation, it became a symbolic representation of the spiny plant described in the Bible used to create the crown worn by Jesus at his crucifixion. Although E. milii is endemic to Madagascar, it had, apparently, been brought to the Middle East before the time of Christ.

Subsequent discoveries in Madagascar have resulted in more than a dozen varieties of E. milii being recognised, having cyathophylls or bracts that range in colour from bright red, to pink, to yellow. Cyathophylls are the large and coloured pair of bracts enveloping the cyathia, often mistaken as flowers. Another well known example of this trait is the poinsettia (E. pulcherrima), where red bracts replace coloured petals.

E. lophogona (Lamarck) has been in cultivation for much longer than E. milii, having been described by Jean Baptiste Lamarck in 1786 from plants that had been introduced into Europe from Madagascar. This species is quite distinctive for its angular stems and longitudinal rows of thorns. This species has much larger and glossy bright green leaves, 12 cm long and 5 cm wide, that are quite leathery, ever-green and are laced with white veins. The inflorescence of this species is usually on stalks, with pink or nearly white flowers. E. lophogona has also been referred to as the ‘white Crown of Thorns’.

Naturally occurring hybrids of these two species were collected in 1959 by Werner Rauh, approximately 50km north of Tôlanaro (also known as Fort-Dauphin) in Madagascar. Rauh devised the name of Euphorbia xlomi for these hybrids; ‘lomi’ being created from the first two letters of the species names of the parents. This name has been accepted and now must be considered to be the formal name of all hybrids/cultivars between these two Euphorbia species.

E. xlomi can be divided into three principal and distinctive groups, for which formal names were proposed by Stephen Jankalski in 2000. These names appear to have generally been accepted and are as follows:

1. Euphorbia xlomi California Group: hybrids originating in California and raised by Edward Hummel from about 1960. These hybrids were first made available by Franklin D Crosby of Crosby Ranch in Malibu, were described as ‘Giant Crown of Thorns’ and included plants described as ‘Rosalie’, ‘Vulcanus’ and ‘Saturnus’. This group were developed for their stout, prominently ribbed stems and larger cyathophylls, but differ from the Heidelberg Group by having E. milii var. hislopii as one of the parents. These cultivars had long leaves that were rather thin and lanceolate.

2. Euphorbia xlomi Heidelberg Group: these cultivars were derived from the hybrids collected by Rauh and described earlier in this article. They were developed by the Institut Systematische Botanik at the Heidelberg University in Germany and were distributed through a commercial nursery in Germany. Names of these cultivars include ‘Somona™’ (sometime mislabelled ‘Sonoma’), ‘Gundula’, ‘Bianca’, ‘Bushfire’ and ‘Gabriela’. These plants had slender, less prominently ribbed stems and smaller and thicker, spatulate leaves.

3. Euphorbia xlomi Poysean Group: over the past 30–35 years, growers in Thailand have developed a complex array of cultivars, having the attributes of both the California Group and the Heidelberg Group. Apart from having a more attractive stout, compact and upright form with large, bright green leaves up to 150mm in length, these cultivars have much larger cyathophylls (up to 5 cm have been reported), with a seemingly infinite range of colour combinations and shapes. The masses of overlapping cyathophylls (clusters of 130+ have been reported) are, colour apart, reminiscent of hydrangeas.

These Poysean cultivars are also known in Thailand as ‘Chinese angels’.

In Thailand, while these cultivars are known as ‘poysean’, this name is in fact the name originally given to E. milii, which has been grown in Thailand for a very long time and is believed to have been introduced into Thailand by Chinese immigrants. The Thai name is derived from the Chinese words “poy’, meaning ‘eight’ and ’sean’, meaning ‘saint’, referring to the eight saints of Chinese mythology. In the Chinese legend of the eight saints, those who respect them receive rewards according to each saint’s power, namely good health, bravery, riches or wealth, beauty, artistry, cleverness or intelligence, poetry and the ability to overcome evil and bad spirits. Thus, Chinese grew E. milii as plant of fortune; they believed that when their plant produced eight flowers in an inflorescence, it brought good fortune to them.

Old E. milii hybrids typically had eight flowers in each raceme, hence the ‘poysean’ name. The Thai believe that keeping Poysean outside their house or on their balcony or terrace brings positive forces to the house and its owner. This explains the popularity of Poysean in Thailand, which lead to Thai plant breeders selectively breeding E.xlomi hybrids for their larger flowers, leading to a new plant form. Poysean fever has already spread to other South-East Asian countries where now each country is producing its own Poysean varieties.

The following represents a brief description of some of the features of the Poysean Group of cultivars:

Raceme types (a ‘raceme’ is a type of inflorescence or flower stalk in which the relative main axis is indeterminate and does not end in a truly terminal flower; it may or may not have lateral branches):

1. Spherical - shaped like a sphere. Can be erect or pendulous;

2. Compound - a shallow arrangement of rows in combinations of two flowers facing upright; and

3. Pendulous - hanging downwards on long peduncles; may terminate in spherical or compound racemes.

Plant Growth Types

1. Compound branching - can be compact or shrubby. These seldom have a dominant erect growth; and

2. Erect - one dominant growth with side or lateral branches.

Flowers

The flowers are unique and lie within the centre of the surrounding cyathophylls, which simulate the calyx and corolla of a ‘normal’ flower. The aggregation of small flowers or florets resembles a single large bloom and is known as a pseudanthium or ‘false flower’, offering biological advantages over a single large flower in terms of longevity and efficiency of cross-pollination.

Examples of the range of ‘flowers’ on Euphorbia xlomi Poysean Group cultivars – Original Photos: Kim Van Tran

Shape

There are a number of shapes that represent the flowers and surrounding cyathophylls:

1. Bowl or cup shaped - is a reasonably recent development;

2. Boat shaped – bracts looking more like an open clam shell; rare, but available in red, yellow and pink;

3. Flat - the most common shape;

4. Wrinkled and flat - another reasonably recent development;

5. Triple or quadrupled bracts – very promising and new development; currently available in reds;

6. Rippled and torn edges – interesting and rare; available in red and pink; and

7. Back-folding – opposite of the bowl or cup shaped where the bracts curl backwards; currently available in red, pink and white.

Flower Size

The flower sizes are separated according to the three main developers; in Germany, the Heidelberg Group, in the USA, the California Group and later in Thailand using a combination of those two breeding efforts and additional stock.

1. Small - less then 15 mm. These are commonly found in strains from the Heidelberg Group (eg ‘Somona™’);

2. Medium - between 15 mm and 20 mm, represented by strains in the California Group. They are usually small, densely flowering, shrubs;

3. Large - larger than 20 mm. These are found in strains in the Poysean Group, but of late the Thais have started to develop some small and medium sized varieties.

Colour

The main colours of the cyathophylls in the Poysean Group are red, white, pink, yellow and green with different hue levels from these main colour palettes, ranging from strong, vibrant colours through to subtle pastel shades. Recent colour development has resulted in the introduction of Poysean cultivars with cream, orange, chocolate and burgundy cyathophylls.

Flowers can either be a single, solid colour, gradient or splotchy bi-colours and tri-colours.

Colours of the cyathophylls of some Poysean Group cultivars can change during their development, due to temperature and light levels. Thus, some varieties have summer and winter colours that are totally different.

Growing Conditions

Conditions: Space plants apart to allow air movement between branches and leaves. This will help with evaporation of extra water droplets collected during watering.

Light: from full sun to 50% well lit shade appears to be the optimum range.

Watering: Poysean Group cultivars are flexible in their watering requirements. As long as the medium is open and well drained, they can be watered regularly. As with any pot plant when watering, it is best to do so thoroughly, until a little water comes out through the drain holes. Allow the medium to dry out somewhat between waterings. Reduce watering to once every 1.5 weeks during winter.

Medium: the ideal medium is one that is open and well drained with some extra manure for added nutrition. The concept is to have a moisture-retaining, yet well aerated and open, medium. For potted plants, the medium should not be compacted which will lessen the incidence of bacterial rot and provide faster growth.

Fertilizer: Regular fertilizing should be applied; fertilizers (those with low nitrogen and high phosphorus and potassium ratios are preferred) will produce less vegetative growth and better reproductive growth and flowers. A generous application of a suitable controlled release fertilizer should guarantee excellent development. Feed during spring and summer to mid autumn and withhold feeding during winter.

Staking: the taller-growing varieties will benefit from being staked, with bamboo or other suitable stakes, in order to stabilize the plants and provide a counterbalance to the weight of the masses of flowers. In the absence of staking, the stems of the plants will be under extreme pressure and may snap under the weight.

While the efforts of the Thai growers have resulted in a spectacular collection of cultivars, it is difficult to say with any precision just how many different cultivars exist. Estimates range from around 200 to in excess of 2,000. The fact that the colour of the cyathophylls can change as they develop, may result in the same plant being given different names by different growers. The absence of a systematic and co-ordinated approach to naming these hybrids, and the lack of compliance with the rules of nomenclature prescribed by the botanical and horticultural codes for naming plants, has resulted in a confused situation with many of the names currently in use having no botanical standing. This confusion has been compounded by commercial nurseries outside Thailand applying their own names.

This state of confusion should not, however, act as a deterrent to anyone wishing to enjoy what are truly remarkable and colourful plants. The pictures accompanying this article are a small representation of the many Poysean cultivars that are available. A good range of these cultivars is available from Canley Vale Nursery, 62-68 Canley Vale Road, Canley Vale NSW.

Kim Van Tran

Bibliography:

Bob Smorley, Giant-Flowered Euphorbia Milii Hybrids, Cactus and Succulent Journal (US) 2000: 72(4): 198-201.

Stephen Jankalski, “Crown of Thorns” Hybrids – Past and Present, Cactus and Succulent Journal (US) 2000: 72(4): 202-204.

Myron Kimnach, Naming the Euphorbia Milii Hybrids, Cactus and Succulent journal (US) 2000: 72(4): 205

Tropica Nursery, The Euphorbia Story: http://www.tropicanursery.com/euphorbia/story.htm

John McLaughlin and Joe Garofalo, Crown – of – Thorns (Euphorbia milii), Fact-sheet No. 65 (2002): Miami-Dade County/University of Florida Cooperative Extension Service; http://miami-dade.ifas.ufl.edu/Programs/commorn/publications/crown-of-thorns-homeowner.PDF.

John McLaughlin, From Africa via Thailand Comes Some Low-Maintenance Garden Color, Urban Horticulture Publications (2002): Miami-Dade County/University of Florida IFAS Extension: http://miami-dade.ifas.ufl.edu/programs/urbanhort/publications/A-Word-or-Two-II.htm

John McLaughlin and Joe Garofalo, Crown - of – Thorns, Euphorbia milii … production & landscape use, Fact sheet No. 63 (2002): Miami-Dade County/University of Florida Cooperative Extension Service; http://miami-dade.ifas.ufl.edu/Programs/commorn/publications/crown-of-thorns-production.PDF.

Top Tropicals in Thailand, Euphorbia milii – Crown of Thorns: http://toptropicals.com/html/toptropicals/misc/thailand/euphorbia.htm

Urs Eggli, Glossary of botanical terms with special reference to Succulent Pants, British Cactus & Succulent Society, 1993.

Gordon Rowley, The Succulent Spurges: A Short Introduction to Euphorbiaceae, 2 The Euphorbia Journal 7-8, Strawberry Press, Mill Valley, California 1982.