Euphorbia obesa, the "Baseball Plant" - Cactus Club

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Euphorbia obesa, the "Baseball Plant"

Plant of the Month > Species E to F

by Bruce Brethauer

       Every now and then, I like to examine some of the plants which are the "standards" of the succulent world; plants which have become so commonplace that we may sometimes forget that these too were once new and exciting plants when they were first introduced, and commanded outrageous prices when they were initially offered for sale. Euphorbia obesa is an excellent case in point: Even though it has only been known to science about 120 years, and has probably always been rare in habitat, it is one of the most commonly grown of the succulent euphorbis today. Today, commercial nurseries can propagate these plants by the tens of thousands, and they are now available at a fraction of the cost that they sold for back when they were introduced into cultivation in the early 1900s.     

       It has been asserted that if a person grows only a single plant of the succulent Euphorbias, more than likely, they grow Euphorbia obesa: such is the popularity of this species. It is the epitome of geometric simplicity: the stems of this species comes the closest to a perfectly spherical ball of all of the succulents which I have grown, earning its common name, the "Baseball Plant". In spite of its simple appearance, closer examination reveals some complexity: the stems are comprised of 8 very shallow ribs. These ribs bear minute tubercles at their centers, from which the flower buds emerge, and its nearly microscopic leaves are produced. The leaves are very short lived, appearing briefly at the growing apex of the plant. The stems are also marked with thin purplish striations - a trait which becomes more pronounced when plants are grown in bright light. With age, the plants may tend to become more columnar. In general, the stems are fairly small, usually growing to about 2 to 3 inches in diameter, although I have seen plants up to about 5 inches or so in diameter, and to about 8 inches tall in the largest plants which I have seen (one grower reports that his plant eventually grew to a height of 20 inches - which is so exceptional that I suspect that his plant may have been of hybrid origin). Unlike the growing habits of most of the other succulent Euphorbias, which tend to branch candelabra-style until they take up a significant amount of table, or floor space, E. obesa typically remains un-branched, remaining compact throughout its life, making it especially suited for growers with limited space.     

       As with most members of the Euphorbia family, the flowering structures (properly called the cyathia) of Euphorbia obesa are tiny, and are produced at or near the growing apex of the plant. If you are looking for a plant with large and exceptionally beautiful flowers, this will not be the plant for you. Male and female cyathia are produced on separate plants, so in order to produce viable seed, at least two plants (one of each gender) are necessary. "Male" plants produce cyathia which bear anthers and pollen, while the "female" plants produce cyathia which bear stigmas, and the seed bearing fruits. The mature fruits of Euphorbias are dry capsules, each containing up to 3 seeds. The capsules burst when the seeds ripen, scattering them up to several yards. Many growers contrived elaborate traps to capture these seed when their capsules burst, as collecting the seed too early (before the capsules became sufficiently dry) would result in extremely low germination rates.     

       These plants are easy to grow, and respond well when given my general growing instructions for cacti and other succulents. But in habitat, Euphorbia obesa frequently grows under larger shrubs, and may be better adapted to, or are at least tolerant of conditions of dapple shade. For this reason, growers in especially sunny regions (such as southern California, Arizona, and New Mexico etc.) may need to provide a bit of shading for this plant: but here in Ohio, this species grows best when provided with very bright conditions. Grown in somewhat lower light, the colorful striations will become less distinct, and the plant may have a nearly uniformly green coloration. At even lower light intensities, the growth will virtually cease, or worse still, the plant may produce etiolated growth, producing weak and leggy stems, so always provide as much light as possible - particularly when growing this species indoors. While not essential, Euphorbia obesa seems to benefit from a period of winter dormancy during which the plant should be kept drier and and somewhat cooler, as this reflects the growing conditions in its habitat. At this time, it will tolerate relatively cool temperatures in the winter (tolerating temperatures as low as the 50's and possibly into the 40's). Growing the plants close to a window (away from heat registers) is usually sufficient to provide the cooler temperatures for a winter dormancy period. In summer, I move my plants outdoors to benefit from the increased temperatures, and increased exposure to daylight. they also seem to benefit from our summer rains. My plants grow best when temperatures are very warm (upper 80's to low 90's), days are long and bright, frequently watered (allowing the soil to become dry between waterings) and regularly fertilized (about once every 6 weeks or so through the summer). Do not subject this plant to extended drought during the summer months, as this corresponds to their growing season, and you will only prevent it from producing its annual growth.

       One complaint which I have heard from a number of growers is that this species will eventually produce significant amounts of "cork" along its stem. It is unclear if this is an indication of unfavorable growing conditions, or if it is just typical of older plants. Since virtually all of the habitat photographs and illustrations of this species show plants with varying deposits of "cork" on their stems, I suspect that this is typical of older plants. Even so, the cork will eventually spread enough to significantly reduce photosynthesis, weakening the plant, and will likely lead to its ultimate demise.  

       In addition to the typical form, crested plants are occasionally offered for sale - in very old crests, the intricate convolutions are reminiscent of brain corals. Seen less frequently are monstrose plants which grow multiple stems from the tubercles on their stems.     

       In recent years, there seems to be a move to consolidate Euphorbia obesa with its close relative, E. symmetrica. For years, these  have been treated as two distinct species, largely on the basis of E. symmetrica having multiple flower peduncles emerging form the flowering "eyes", while only one is produced from each "eye" on Euphorbia obesa. There are also some additional differences in their roots and stems, but since there is variation in both species, no clear distinctions could be drawn between them on the basis of these features alone. While I'm not certain if this is becoming a widely accepted view, I have seen several recent articles which have consolidated the two species, identifying them as Euphorbia obesa v. obesa, and Euphorbia obesa v. symmetrica respectively.     

       The interesting stems of this species makes it a particularly desirable plant, especially to those growers who look upon their plants as living sculptures. But is is also a very easy plant to grow, presenting few challenges or problems - as a rule it is pretty insect resistant, its stems offer few hiding places where insect pests such as mealy bugs and scale can become established - and even if they do get a foothold, they are usually discovered fairly early, and can be easily removed with a Q-tip soaked in alcohol. The smaller size of their stems makes Euphorbia obesa  a good candidate for the windowsill, and its complete absence of spines will also endear it to many growers. One cautionary note: like all members of the Euphorbia family, Euphorbia obesa produces a milky latex, possibly causing skin irritation if the latex should come into contact with it - and it may possibly be toxic if accidentally ingested, so the "Baseball Plant" may not be suitable for every household, but it is a deservedly popular plant, a good introductory species for growers who have not yet grown euphorbias.
       Euphorbia obesa was first "discovered" by Peter MacOwan in 1897. Unaware that he had collected a species which was new to science, he labeled the plant "Euphorbia meloformis" and sent it onto the Royal Gardens, Kew. This plant first flowered in 1899, at which time a botanical drawing was made, which later accompanied the original description of the plant (published in 1903). This plant died shortly afterwards, and it would be nearly 20 years before Kew replaced it. Subsequent searches of the type locality on a few farms near Kendrew in the district of Graaf Reinet in South Africa, revealed several additional localized, and rather small populations. Demand for plants soared shortly afterwards, and plants were collected by the hundreds from these populations to satisfy the demands of collectors throughout the world. The prices which these plants commanded were considerable: the few plants which found their way into the United States were sold at $27.50 in 1925 - a relative fortune to pay for a plant in those times.
       The high prices commanded by these plants drove a significant trade of field collected specimens, and impacted the wild populations to such an extant, that the species was considered endangered as early as 1915. Experts predicted that the species could become extinct in habitat if the export of plants continued. Interest in preserving the remaining wild plants prompted the South African government to impose an embargo on all field collected plants of E. obesa in 1931. Despite these efforts, other pressures, including loss of habitat due to agriculture and land development, predation by grazing animals and baboons, and the continued illegal harvesting of plants in habitat prevented a rapid recovery of the wild populations, and for many decades, the species continued to hang near the brink of extinction. It has only been in recent years that some of the wild populations have finally begun to recover significantly - The species continues to be protected by the South African government, and is protected by CITES, permitting only very limited trade in field collected plants, with government monitoring of the wild populations to assure that even this  limited trade in plants is sustainable.     

       But Euphorbia obesa  is such an easy plant to grow and propagate (each female plants can easily produce hundreds of seed every year, and under greenhouse conditions, germination rates of 95% and higher are possible) that the need for field collected material was virtually unnecessary from the start, but at the turn of the century, there was little interest in protecting wild populations, and most commercial greenhouses were not in the habit of propagating plants which could just as easily be legally gathered from the wild. In time, following the embargo on field collected plants, the techniques for pollinating flowers, collecting seed, and germinating seed were perfected, and commercial growers found that they could propagate enough plants to satisfy the growing demand for these plants, and at prices considerably lower than the field collected specimens. An added bonus was that these greenhouse grown plants were usually healthier, and more uniform, and less scarred than the field collected plants: also, since they had been grown in pots from the start, seed grown plants did not suffer from the transplant shock typical of plants gathered from the wild. In all, it was a win-win situation for collectors, commercial growers, and the wild populations of this species.     

       We may fool ourselves into the belief that in our modern times, people are generally better informed and may be more sympathetic to the ideals of conservation than the people of past decades. We may also believe that the international laws restricting the trade in endangered species will effectively limit the trade in newly described and rare plants, but sadly, this is just not the case. Time and again, we see the same cycle played out: following the discovery of a new and interesting species, there is wanton destruction of wild populations by irresponsible plant collectors until the species is pushed to the very brink of extinction. Eventually, intensive propagation by commercial growers will satisfy public demand for particularly choice species, and prices ultimately fall to more rational levels. But until the commercial nurseries are able to propagate newly discovered species, their populations are vulnerable to the illegal trade in endangered species. Following their discoveries and re-discoveries (as in the case of Euphorbia turbiniformis), the wild populations of Euphorbia piscidermis, E. gymnocalycioides,  Ariocarpus bravoanus, and possibly Astrophytum (Digitostigma) caput medusae, and Geohintonia mexicana,  have been decimated as a result of illegal collecting. This is in spite of changes in the rules for publishing new species - which now allows for the substitution of a generalized type locality for the species. In this way, it was hoped that the specific locality of the species could be kept secret for a time so that measures could be taken to propagate the plant to provide plants for collectors, and to provide greater protection for the wild populations. But in at least several cases (such as Ariocarpus bravoanus), the wild populations were eventually located, and collectors harvested practically every plant. It is unfortunate that growers still need to be concerned about the sources of their plants, but this continues to be the case. It is only by insisting that our plants are either propagated from nursery stock, or (when collected from the field), are collected entirely in accordance with international laws that these rare species can be protected in habitat. It is a tall order - many growers are particularly interested in species which are new to science, or plants which are localized or rare in habitat. Some demand older, specimen sized plants, which may take a number of years to produce in the nursery, some growers even choose to grow particularly rare species with the intent of propagating additional plants to trade or sell to other collectors, to reduce the illegal trade, and give wild populations an opportunity to recover. Whatever the intent, it is still very important that collectors be aware of the sources of their plants, lest they inadvertently support the illegal trade of field collected specimens - particularly in the cases of plants which have been recently published. This is not to say that these other efforts to protect species are of little use - they are useful methods to provide some degree of deterrents to perhaps limit the harvest of wild plants. The example of Euphorbia obesa illustrates one important point: some species may require many years of monitored protection in the wild before they naturally increase their numbers. In this instance, there is some evidence that these protective measures finally worked, but natural recovery can indeed be long and slow.

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