Species of flowering plant
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Euphorbia stygiana (Portuguese: Trovisco-macho) is a species of evergreen shrub in the family Euphorbiaceae, endemic to several islands of the Azores. It has a critically endangered subspecies (subsp. "santamariae") with only 20 known remaining mature individuals in the wild.
Description.
"Euphorbia stygiana" is an evergreen shrub with low but robust serpentine, green stems; white-veined, thick, leathery blue-dark green leaves and large yellow-green flower heads which are strongly honey-scented in spring and summer (from May to June). It can grow up to about tall in its native environment but is often tall and spreads to about wide.
The leaves are long, slightly pubescent on the bottom side. The fruits are , striated, subglobous and warty. During cold winters (especially outside its native range) these leaves may turn to a brilliant crimson colour.
It is hardy down to USDA Zone 8b: to and can be propagated through stem cuttings.
Distribution and habitat.
"Euphorbia stygiana" is endemic to all Azorean islands except Graciosa where it inhabits the extremely humid highlands of the archipelago from in altitude, especially on Pico Island, in sheltered places such as ravines, craters and dense laurel-Juniperus forests.
Subspecies.
There are two known subspecies: 
Threats.
The species is mainly threatened by agricultural development, change in land use, and invasive species and the subsequent increase in competition.
Toxicity.
Like other members of the "Euphorbia" genus, "E. stygiana" has a milky white sap that may cause skin irritation or allergic reaction when in contact with the skin or eye. It is toxic if eaten.
References.
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