Hippeastrum aulicum is native from Brazil south to Paraguay. It is an epiphytic species and grows on rocks and large trees in its native environment. Sometimes it can be found on the ground. It generally has a robust form with thick leaves, thick peduncle and large flowers. Because of its widespread distribution, there are many forms, some of which are available in cultivation. This species is evergreen, holding its leaves through a short summer dormancy. Water sparingly during dormancy (late spring) and commence regular watering in August (late summer). The plant appreciates fertilizers during active growth. It usually blooms in autumn to winter. Officially, there are two varieties var. glaucophyllum and var. platypetalum, and one form f. robustum. However, unofficially in cultivation, there is another form with thinner petals known as f. stenopetallum.
Original species description from Handbook of the Amaryllidaceae, J.G. Baker 1888:
Bulb ovoid, 7.5 cm (3 in.) diam.; neck short. Leaves 6-8, lorate, bright green, 45 cm (1.5 ft.) long, 3.8-5 cm (1.5-2 in.) broad. Peduncle stout, terete, 45 cm (1.5 ft.) long. Umbel generally 2-flowered; spathe-valves lanceolate, red-brown, 7.5-10 cm (3-4 in.) long; pedicels 3.8-5 cm (1.5-2 in.) long. Perianth limb 5-6 in. long; tube short, with a distinct incurved green corona at the throat; segments bright crimson, green at the base; outer segments and lowest inner about an inch broad above the middle; 2 upper inner much broader. Stamens shorter than the segments; filaments bright red; anthers 1.3-1.9 cm (0.5-0.75 in.) long. Style as long as the segments; stigma deeply trifid. Var. tenopetalum has all the segments much narrower than in the type.
Hippeastrum aulicum ex Corupá, Southern Brazil. The photos were taken May 2006 by Tarcísio Eduardo Raduenz of plants in habitat.
Hippeastrum aulicum f. robustum is as the name describes, a robust form with large leaves and robust flowers. The photos below were taken by Nhu Nguyen. The plants were grown in Berkeley, California and blooms around the end of December each year. The purple stamens seen in some of the photos show a distinguishing characteristic of this species.
The first photo was taken by Angelo Porcelli who wrote that it is a very rewarding species to cultivate and blooms reliably every Christmas in his climate. The next photos were taken January 2004 by Lee Poulsen the first time they bloomed. He wrote: "It's kind of nice getting such a pretty hippeastrum bloom naturally outdoors in the middle of winter." The last photo was taken by Doug Westfall.
This photo compares the forma known as robustum or platypetalum on the left and the form 'Biritibi' on the right. Note that Biritibi has red marks in the throat, while robustum is totally green. Photo and text by Angelo Porcelli.