This semi-tropical shrubby plant from Mexico and Guatemala, known as poinsettia, is often seen as a dwarfed potted specimen at Christmastime, but its natural growth is as a shrub up to 3.5m tall. The bright red bracts are clustered into the shape of large flowers, lasting for many weeks in winter. It will bloom best in full sun with fertile soil. There are various cultivars in shades of cream and pink; and there is a double red form, called 'Henrietta Ecke' (possibly named after the mother of Paul Ecke; Paul Ecke bred and popularised dwarf forms poinsettia as an indoor plant for Christmastime in the USA in the 20th century), which seems to be in bloom for a very long time. It is effective grown with red Camellia japonica cultivars and Salvia gesneriiflora 'Tequila'. The annual Euphorbia cyathophora growing nearby will give an effective echo of its blooms on a smaller scale.
It should be pruned back hard in late winter, and tip-pruned in mid-summer for more compact growth. It can be propagated from cuttings taken in late summer. All Euphorbia have an irritant sap in their stems so take care when handling these plants and always wear gloves when pruning. Be very careful not to get any sap in your eyes as this can cause damage to them.
The common name of 'poinsettia' is after Joel Roberts Poinsett, American Ambassador to Mexico, who introduced the plant to the USA in 1828. The plant was used for medicine and dyes by the Aztecs.
If you plan to have a dwarf potted poinsettia as a Christmas decoration indoors, water the pot only when the surface of the potting mixture feels dry, and position it where it will receive plenty of natural light but is away from draughts. The plants are forced into bloom using special methods, so it won't flower again next Christmas; however, you could try planting it in the garden and see what happens!