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Excerpts from Jim Conrad's
Naturalist Newsletter
entry dated March 1, 2022, issued from near Tequisquiapan, elevation about 1,900m (6200 ft), ~N20.57°, ~ W99.89°, Querétaro state, MÉXICO
LEATHERSTEM / WITCH'S FINGERS
Somewhat spottily, where the soil is thin atop the underlying rock consisting mostly of weakly cemented volcanic ash and sediment from nearby rhyolite hills, small populations of what's shown below turn up:
This is the Leatherstem, JATROPHA DIOICA, recognized in the field during the dry season by its gray, slender, tough-leathery stems about knee high. Here it's leafless most of the year, but after a good rain quickly sprouts leaves and looks very different from the photo. Leaves, flowers and fruits arise from short, knobby shoots along the stem.
In Spanish often it's called Sangre de Drago, or "Dragon's Blood," because like so many members of its Euphorbia Family when it's injured the wound bleeds a watery latex which can be blood red, I read, if the wound is on an older stem's lower parts and rhizomes. With a thumbnail I cut a shallow wound midway up a stem, producing what's shown below:
Traditionally, infusions of Leatherstem's branches and roots have been commonly used for dental problems such as tooth decay, gingivitis, loose teeth, bleeding gums, and toothache. A 2019 paper by Gutiérrez-Tlahque and others found that Leatherstem extracts contained compounds such as alkyl esters of acetic and ferulic acid, as well as the diterpenes citlalitrione, jatrophatrione, jatropholone A, and jatropholone B, which they suggested could be the cause of observed antioxidant and fungicide activities responsible for its traditional medicinal use.
Leatherstem is native just to arid southern Texas and northern Mexico.
entry dated April 22, 2022, issued from near Tequisquiapan, elevation about 1,900m (6200 ft), ~N20.57°, ~ W99.89°, Querétaro state, MÉXICO
LEATHERSTEM FLOWERING
Now during the driest part of the late dry season, there having been no rain since around December, the mostly leafless Leatherstems are producing flowers. Leatherstems come in male or female plants. Since the plant spreads by rhizomes, often a big patch of Leatherstems will actually just be one plant consisting of numerous sprouts connected below ground, and all the sprouts will bear unisexual flowers -- all of the flowers either male or all female. Below, you can see male flowers with half of their ten stamens extending beyond the corolla's mouth. Five shorter stamens are hidden deeper inside the corolla.
Leatherstem's female flowers are fairly similar to the male, but if you look closely you find inside one, instead of stamens, a green ovary, the future capsular fruit, the ovary:
Once the female flower is pollinated, the ovary begins growing, and the corolla falls away.
The above picture shows different stages of development soon after pollination. Notice that first the rosy calyx below the white corolla keeps its toothed sepals pointing upward. After pollination, the corolla withers and fall away, while at the same time the sepals begin to spread apart, until the green ovary looks as if it's in the center of a burgandy-colored starfish.