March Plant of the Month, 2006 (Euphorbia obesa)

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March Plant of the Month, 2006 (Euphorbia obesa)

Post by templegatejohn »

Euphorbia obesa Hook. f.

Growth Habits:
The plant is globular at the start of its life and will remain so for several years, until after this time it slowly begins to become more columnar. The body of the plant is a dullish green and is covered in what is general described as a ‘tartan’ pattern. The plant usually has eight ribs and depending upon the specimen they can be greater or less prominent but are never really deeply defined, hence the baseball nickname. The plant has a large tap root and should be potted accordingly. Although I don’t normally go in for giving plant sizes as this very much depends on locality, growing conditions and how far the owner is prepared to bend the truth, a plant of 6in. diameter is a pretty good specimen. These plants do not look good ‘pumped up’. OK Joe Bloggs can grow them to 10in. But the point is Joe . . . they shouldn’t be 10in.

Scientific name: Euphorbia obesa

Family name: Euphorbiaceae

Common names:
Baseball Plant, Sea Urchin

Synonym: Unknown to me.

Etymology: The genus Euphorbia was established by Linnaeus in 1753 and commemorates Euphorbus, the 1st century physician to King Juba II of Mauritania, who is thought to have used plants, such as Euphorbias, as medicine.
Obesa: The specific name means fat.

Origin: South Africa (Great Karoo)

Light: Light shade seems to suit the plant best, but it will take the morning sun if not too fierce.

Any good general compost should suit as long as it is open and a little more rich than some species require.

Water: Needs water in moderation in the summer, but becomes dormant in winter and must be kept dry.

Flower: The flowers are small and yellow and delicately scented, but relatively insignificant, apart from the fact that some plants are male and others are female, which plant is which can be told by the shape and form of the flower. Because of the separate male and female plants the species is known as dioecious and not just two clones but a male and female are needed to produce seed.

Fruit: The fruit is in fact a green capsule, anything up to 7 mm. in diameter and when ripe will burst open with a sharp crack (quite audible if you are in the greenhouse at the time) and the large seeds are thrown several feet in all directions.

Min. temp: Roughly 10°c-50°f. Not too critical if the plant is kept quite dry.

Cultivation: This particular species has a habit of ‘dropping’ its roots if reasonable care is not taken with the watering programme. One of the major problems I have found, having grown many of them from seed over the years, sometimes even seedlings coming up in pots containing other plants, due to the habit of the seed being projected several feet from the plant, I digress . . . If the weather in the middle of summer becomes too hot and remains so throughout the night as well as during the day the plants sometimes decide to go into a state of what can only be called semi-dormancy. Watering at this stage is not only a waste of time, but is detrimental to the plant and its root system. How do you tell when this phenomena is occurring? Well the only advise I can give, is if you cannot see any sign of growth on the plant, usually lighter coloured epidermis in the ribs, flowers or flower buds, then do not water it.

Habitat: The plants occur in karoo vegetation among Beaufort shale fragments, where they grow in full sun or in the partial shade provided by dwarf karoo shrubs. They are very well camouflaged and difficult to see. The habitat is very stony and hilly with summer rainfall ranging from 200-300 mm per annum, falling mainly in thunder showers. Summers are very hot: the average daily maximum about 26 degrees centigrade and the minimum about 11 degrees centigrade.

Comments: Euphorbia obesa is a plant that is easily obtained and very popular in cultivation and yet almost extinct in the wild due in the main to over zealous collectors and also destruction of its habitat for whatever reason. As I said above they are very popular and have an almost ‘Teddy Bear’ like quality. People go Oh . . . It’s lovely, and want to cuddle them. Not a good idea, as like all other Euphorbias they are poisonous, but I can understand where they are coming from and always have several in my collection. I recommend you get one, or if you really want to sex up your succulent collection 2. Just make sure ones male and the other one isn‘t, or vice versa. The Euphorbia family contains some of the most diverse plant life on this planet, well over 2,000 species, but obesa has got to be the most succulent of them all.