bracts (red leaves) of the wild species are much narrower than those of
the cultivated species.
||This image shows
how poinsettia grows into a small rangy tree in the wild. This one was
photographed under a large Enterolobium tree in Chiapas, Mexico.
||This is a side
view of an inflorescence from the same plant as in the above photo. The
photos were taken in a canyon in southern Chiapas, near the southern
extreme of the species.
||The habit of
poinsettia is shown in a closer view of the same tree as in the above
branches of poinsettia are often long, thin, sprawling and nearly viny.
This individual was flowering with wild morning glory in Chiapas,
often flower when leafless or nearly so. This tree is covered with
leaves during the summer rainy season.
wild poinsettias in southern Oaxaca in January.
||Poinsettia often grows on very steep slopes. This Oaxacan population had large numbers of individuals, but was very difficult to collect because we didn't have our rappelling gear with us.
|We recently discovered a wild population of poinsettias with white bracts growing on limestone on a steep slope in tropical dry forest in western Mexico.||The undergrowth in poinsettia localities is often so dense that it it difficult to see the entire plant. This individual was growing exposed in all its lanky glory, showing how rangy and cane-like wild poinsettia usually are.
|This photo gives an idea of what wild poinsettias look like in their habitat at the height of the dry season. This population was in flower in March, along with a pink-flowered species of Erythrina.||This image shows the densely wooded, steep hillsides that wild poinsettias usually are found on. The poinsettias dot the gray woods with yellowish white inflorescences.|
|We have visited this population on more than one occasion and have found it in flower in March in two different years.
This closeup of an inflorescence from the recently-discovered white population shows the very beautiful bracts of these plants.
|The subgenus Poinsettia within the genus Euphorbia is distinguished by having a single large two-lipped gland on the cyathium.
||This image and the one on the left show details of the cyathial gland of Euphorbia pulcherrima. This image also shows the female flower recurving and beginning to mature into a fruit. If you look closely you can also see some of the bristly male flowers.
|This red-bracted population grows not far from the white population above. The plants grow on a low, steep cliff that is very dry and fully exposed to the sun in the dry season.||This image shows an inforescence display of the red-bracted population shown at left. You can see a developing seed capsule near the middle of the image, as well as some of the globs of latex the plant inevitably secretes upon damage.|
|Here you can see the cyathial glands of Euphorbia pulcherrima from the red-bracted population above in detail. Remarkably, nothing is known about the pollinators of this plant.||This image shows a very young fruit in the middle, a slightly older one at left, and a nearly mature one at right.|
|The rugged mountains of Jalisco state are also poinsettia country. This population was growing at the transition between tropical subdeciduous forest and pine-oak forest.
||Poinsettias don't look like much in fruit. Like many dry tropical forest plants, they usually flower at the height of the dry season and their seeds disperse shortly before the rainy season begins. This photo shows a poinsettia fruiting leafless in a lonely Jalisco canyon.
|Mark and Laura studying a wild poinsettias in a deep canyon in Jalisco, about 75 km from the above locality. This is one of the largest poinsettia populations we have found to date, with several hundred individuals.||When we visited the population at left in February, there was only one scraggly inflorescence. This huge population must be spectacular in when in flower.|
|This wild poinsettia is from a remote sierra in Guerrero state. Our work indicates that this population has the same haplotype (genetic variant) that is found in most or all domesticated poinsettias.||Poinsettia localities are often very beautiful places, like this deep, shady Guerrero canyon where throngs of poinsettias flower next to Chamaedorea palms under bowers of wild bamboo.|
|Populations of poinsettia in the wild are often very small, with less than 20 plants, which makes dense masses of plants such as this large Guerrero population all the more striking.||Poinsettia often grows on very steep slopes, as it does atop this rocky face in Guerrero. Here the plants are growing with a red-trunked Bursera species and an Anthurium, both at left.|
|About 100 km as the crow flies from the above population but over a formidable mountain barrier grow a series of poinsettia populations that include this one. Here you can see bright red poinsettia bracts in the middle canopy level of the woods.||Like all poinsettia populations, these individuals grow in tropical deciduous forest in canyons. Practically nothing is known about how traits of economic interest such as bract shape and color vary between wild populations.|
|Euphorbia strigosa is a striking miniature poinsettia species that grows in many parts of western Mexico. It has very long, brittle stems that creep along or under the ground and spring from an underground tuber.
||This species usually grows at higher elevations than the poinsettia Euphorbia pulcherrima. This population was growing in the understory of a pine forest.
|This lovely species is restricted to a tiny area in the state of Guerrero, Mexico. It has a much more compact habit than E. pulcherrima and grows at elevations that average about 1000 meters higher.||The beautiful white inflorescence displays of Euphorbia cornastra appear in the summer rainy season, rather than the winter dry season as in the Christmas poinsettia.|
|Because it flowers in the rainy season, E. cornastra always has leaves when it flowers. The dark green leaves constrast stronly with the brilliant white bracts.||When in flower, Euphorbia cornastra is conspicuous even from far away in the highland tropical scrub where it occurs. Several individuals can be seen at middle bottom.|
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Biología, Universidad Nacional Autónoma de México
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