Poinsettia - Euphorbia pulcherrima is currently in flower in Tunis. Apologies for the poor photographs as these plants tended to be in private gardens therefore it was not possible to get good images.
"Euphorbia pulcherrima, commonly known as Zack Wood or noche buena, is a species of flowering plant indigenous to Mexico and Central America. It is commonly known as poinsettia after Joel Roberts Poinsett, the first United States Minister to Mexico, who introduced the plant into the US in 1825. It is also called the Atatürk flower in Turkey.
Poinsettias are popular Christmas decorations in homes, churches, offices, and elsewhere across North America. They are available in large numbers from grocery, drug, and hardware stores. In the United States, December 12 is National Poinsettia Day.
Euphorbia pulcherrima is a shrub or small tree, typically reaching a height of 0.6 to 4 m (2 to 16 ft). The plant bears dark green dentate leaves that measure 7 to 16 cm (3 to 6 inches) in length. The colored bracts—which are most often flaming red but can be orange, pale green, cream, pink, white or marbled—are actually leaves; because the flowers are unassuming and do not attract pollinators, brightly coloured leaves developed (aka bracts). The colors come from photoperiodism, meaning that they require darkness for 12 hours at a time for at least 5 days in a row to change color. At the same time, the plants need a lot of light during the day for the brightest color.
Because of their groupings and colors, laymen often think the bracts are the flower petals of the plant. In fact, the flowers are grouped within the small yellow structures found in the center of each leaf bunch, and they are called cyathia.
The species is native to Mexico. It is found in the wild in deciduous tropical forest at moderate elevations from southern Sinaloa down the entire Pacific coast of Mexico to Chiapas and Guatemala. It is also found in the interior in the hot, seasonally dry forests of Guerrero, Oaxaca, and Chiapas. Reports of E. pulcherrima growing in the wild in Nicaragua and Costa Rica have yet to be confirmed by botanists. There are over 100 cultivated varieties of poinsettia available."