Echinopsis bridgesii is a common roundish cactus with many verical ribs. Here it grows in a pot (on the left) in the company of a small Opuntia (on the right). It likes to make lots of babies, four of which are visible along the rim of the pot. It is not very conspicuous - until it decides to flower. The flowers look like 10 cm long gloriously beautiful trumpets, but they last just one day (barely enough for the little wasp to take a full advantage of them). Notice the bud of a third flower which just started forming in between the two open ones. It will develop and open in about three days.
 
To make cactuses flower in Spring or Summer, treat them properly during Winter. Keep them away from direct light (but not in a complete darkness) in a cool, reasonably aired place and, above all, do not water them at all.

My home, June 2006