(Editor's Note: This article was originally published on June 14, 2009. Your comments are welcome, but please be aware that authors of previously published articles may not be able to respond to your questions.)
Jatropha is a large genus in the Euphorbiaceae family, primarily of Central American origin with many species extending into the very southern United States (and at least one species is native to Madagascar.) Of the approximately 175 species, only a handful are known in cultivation and few have economic importance. Most of the species I am interested in are grown strictly for their ornamental value. Most Jatrophas are evergreen shrubs to small trees with tropical growing requirements. However some are hardy in cooler Mediterranean climates where they are at least ‘semi-deciduous' (deciduous when it's cold enough, but evergreen in warmer years.) All appear to be at least somewhat drought-tolerant, with some being extremely so, and these have a tendency towards succulent as well as woody stems.
As mentioned, some Jatrophas have economic importance, usually either medicinal or as a foodstuff for livestock and, rarely, people. Typical of members of the family Euphorbiaceae, Jatrophas have toxic sap (contains lectins, saponins, phorbol (carcinogen) and a trypsin inhibitor) which can also be quite irritating to handle as well. Some plants are extremely toxic with ingestion of just a few seeds causing death in an adult. One species has been grown in large crops for a source of biofuel (Jatropha curcas) and several successful flights have been recorded on spiked Jatropha oil fuel. Problems with manufacturing Jatrophas economically and dealing with their problematic toxicity will probably keep this genus from realizing its global potential as a replacement for petroleum.
From a purely ornamental point of view, some species are rather common in cultivation and make attractive landscape or potted plants. Most of these are rather easy to ‘bonsai' and able to withstand neglect better than than most potted plants. However, some Jatrophas are rather easy to kill from the opposite problem--overwatering. But in my careless hands, most of the Jatrophas I have tried to grow have managed to survive despite my best efforts to kill them off.
The following are few of the Jatropha species one might be most likely to come across, at least in the U.S.
Jatropha cardiophylla, J. cinerea and J. cuneata are three Mexican species that can be found in southern Arizona as well. As a group these three species are known as Limberbushes. They are also sometimes referred to as Dragon's Blood or Sangre de Cristo, due to their unique blood-red saps. These plants are sometimes used in landscaping as they are all short, very drought-tolerant, deciduous shrubs. They seem pretty gopher resistant as well, thanks to their toxic saps. The saps are sometimes used to tan hides (very astringent) but they have a number of medicinal uses as well, from wound treatment to treating diarrhea. I have no experience growing any of these species of Limberbush but they seem relatively hardy for growing in southern California; all have a USDA rating 9a to 9b, or 20F to 25F (-6 to -4C).
Jatropha cardiophylla (all photos Xenomorf)
Jatropha cinerea in southern California
Jatropha cuneata in Mexico (photo CactusJordi); plant in southern California in spring; close up of leaves
Jatropha cathartica (aka Jatropha berlandieri) is a popular but somewhat finicky and rare caudiciform species from Texas and Mexico. I have rotted every one I have tried to grow, but that does not necessarily mean it is a difficult plant. It is a very small plant, barely making to a foot in height at maturity. Its stem is nearly a perfect sphere with a short vertical projection upon which arise a half dozen or so petioles with deeply cut, irregular leaves and some bright red flowers on even longer stalks. This is a zone 10a or 10b plant (minimum temp around freezing) and is prone to rot in cool winters.
Jatropha cathartica stem on left (photo Xenomorf); sale plant showing flowers; third photos shows deeply cut leaves (photo Kell)
Jatropha curcas (aka Physic Nut) is one of most useful, economically speaking, of the Jatrophas. This plant is originally from either northern South America or Mexico, but its exact origins are unknown and it is now common all over the world, including Africa, Asia and even Florida. This shrubby tree has a very high oil content within its saps that many have been hoping this plant will be a valuable future source of biofuel. The tree is very drought-tolerant, easy to grow and fairly pest resistant. However its toxicity issues have kept it from being the new ‘green' fuel. I have never grown this plant but it seems to be a fairly easy plant to cultivate, flowering predictably and it has a hardiness down to 20F (-6C). For more on this, see these articles from researchSEA.com and Reuters.
Jatropha curcas (first photo cactus_lover and second BigOHort); Physic Nut 'nuts' (seed pods) (photo cactus_lover)
Jatropha gossypifolia (aka Belly-ache Plant) is a highly toxic species grown for its ornamental value, although it is a moderately invasive species here. In more tropical climates this is a serious weed, both in terms of invasiveness as well as danger to grazing herbivores. It has attractive maroon new leaves and makes a neat, low shrub. In my garden this plant tends to show up everywhere, though it is an easy weed to pull up, so I am not offended by it. Flowers are scarlet but somewhat small and not terribly showy. Leaves tend to be sticky to the touch. It is listed in some sites as being a zone 10 plant, but PlantFiles lists it as hardy to zone 8a. I think the truth is somewhere in between, as mine was damaged by a freeze into the mid-20s (making it, at best, a zone 9b). It is a very drought-tolerant species and one can easily grow it as one would a typical arid-loving Euphorbia. However it is very tolerant, and even seems to prefer, warm, humid, rainy climates.
Jatropha gossypifolia new leaves (photo artcons) on left; large shrub (photo cactus_lover); and flowers (photo cactus_lover) on right
Jatropha integerrima (aka Spicy Jatropha, Peregrina). I have only tried to grow this plant once and it seemed to resent my arid climate. However most who have tried growing this plant in similar USDA zones but with more humidity have found it to be an easy plant to grow. Of all the Jatrophas I have personal experience with, this is the least succulent-like of them. It looks more like an ordinary small shrub with bright red to reddish pink flowers and ordinary ovoid leaves. This is an evergreen Jatropha originally from Cuba. It has moderate cold hardiness (25F or -3C) and reportedly is drought-tolerant (though mine did not seem to be that outstandingly drought tolerant). It is a common plant and can frequently be found at garden centers on the East Coast, but seems pretty uncommon in California.
Jatropha integerrima (photo cactus_lover on left; decklife in middle; and IslandJim on right)
Jatropha mahafalensis is a Madagascan native, an oddity among Jatrophas. I have had one growing in my garden in zone 9b in southern California for several years now, and though it took a big hit when the temps dropped to 25F (-6C) for nearly half a day, it survived and has looked great since. This is a succulent, branching shrub that seems to be stopping at about six feet in height (in my arid, cool climate), but can grow over ten feet tall in a warmer climate. This plant is also deciduous in my climate. Flowers are dinky yellow things (though potentially more ornamental in more humid climates) and not very noticeable. I have yet to see my plant produce a seed, but it's fairly easy to grow from stem cuttings, and is a very fast growing plant.
Jatropha mahafalensis in my garden: first photo as seedling; second just 6 months later and third after freeze
Flowers of Jatropha mahafalensis in my yard (first two photos) and in Florida (photo barrystock)
shot of Jatropha mahafalensis stem showing greenish transluscent sap oozing from small injury- toxic!
Jatropha mcvaughii is a Mexican tree that is fairly rare in cultivation, but I see seedlings for sale in the local Cactus and Succulent society meetings. A local arboretum, Huntington Botanical Gardens, has a mature tree which produces a huge number of seeds yearly and I would not be surprised if that were the source of most of these plants. This is a pretty slow-growing species (my seedlings grow about one to three inches a year) and rot if overwatered in winter (though rain water rarely seems to produce any such ill effects). Cold tolerance seems to be about 28F (-4.5C) but it can survive colder temps, growing back from undamaged stems.
Jatropha mcvaughii tree in Huntington Gardens with close up of leaves in second photo; my own seedling in summer (just a naked stick in winters)
Jatropha multifida, or Coral Plant is less common than Jatropha integerrima, but it is not rare. I have grown this one several times, but in zone 9b it is a very marginal plant. I think listing it as a zone 10a would be more realistic (minimum temp of 30F or -1C). This is a succulent-stem species that has a lot of tolerance, even preference, for climates with a high humidity (grows happily in Hawaii) where it is always warm. There it grows into a large shrub up to eight feet tall (rarely as tall as twenty feet). In the more arid, cooler climates, it tends to be less branched and seems to stay smaller and is definitely deciduous (it is not a deciduous plant in climate zones where the temperatures do not get below 40F (4.4C)). It needs a well draining soil and will rot easily in cold, damp soils that drain poorly in winter. This Mexican and South American plant is characterized by its palmate, deeply cut, almost lacy leaves and brilliant red-orange, small, spikey flowers year-round. It is an excellent species for pot culture.
Jatropha multifida in Hawaii first photo; showing deeply dissected leaves (middle photo salvia_lover); and drooping mature leaves in right photo
potted plants (photo brianich) and flowers/ seed pods
Jatropha podagrica or Buddha Belly Plant is perhaps the most commonly grown of all the Jatrophas, and typically grown in containers. This Guatamalen plant is grown for its peculiar swollen stem, though it has nice flowers as well (very similar in all respects to the flowers of Jatropha multifida). This is another deciduous plant in my climate, and another 10a (-1C or 30F) plant, though I get away with keeping it outdoors in winter as long as it's near a building and in full sun in winter. Seed pods are known for their explosive jetting of seeds several feet in all directions. Some confuse this plant for a Pachypodium here in Southern California where they look somewhat similar in winters.
Jatropha podagricas growing in ground (in tropics)(photo mico58); middle photo of stem in winter, my garden; third photos is of flowers and seed pods (photo Monocromatico)
Jatropha podagrica leaves (upper side, and whitish undersides)
There are many more Jatropha species in cultivation, but they are pretty rare and I have no personal experience with any of them.
a few other Jatrophas: Jatropha cordata in the southwest US, Jatropha dioica (photo SSurgot), and Jatropha paradoxa in Huntington Gardens, California