Arum cornutum is a trade name for the voodoo or dragon lily. The plant is an aroid and its scientific name is Sauromatum venosum. The lily is a perennial that produces an amazing flower. It is a deep purple spathe with a black spadix. The spathe may be mottled with cream or light green and the leaves are deeply lobed and similar to a split leaf philodendron. The spadix produces a rather obnoxious smell like rotting meat that attracts pollinators. Arum cornutum is grown from a tuber and is related to the huge, and also smelly, corpse flower.
Choose a shady to partially shady location for the plant. Dig a trench at least 6 inches deep and fill it with water to check the drainage. Let it drain and then fill it again. If the trench drains the second time within half an hour, the location you have chosen has enough drainage for the tubers.
Perform a soil test to ensure the pH is adequate for the arum. The voodoo lily grows best in acid to neutral soils. If your soil is too sweet and alkaline, you can work in some sulphur to lower the pH and increase acidity. The amount will depend on the result of the soil test. Follow the instructions on the bag of sulphur.
Dig in 3 to 5 inches of compost to improve the soil and provide nutrients. Work it in to a depth of at least 12 inches. Make a hole 6 inches deep and place the tuber in the hole with several of the growth nodes or bumps facing upward. Cover the tuber and compress the soil into the hole.
Provide 1 inch of water per week once the plant sprouts. Keep weeds away from the plant by at least 6 inches to prevent competition for resources.
Place a stake near the stem of the flower as it develops. The flower can reach 18 inches long and it is heavy. The speckled stem may need support during bloom time in spring to early summer. Secure the stem to the stake with plant ties.
Dig up the tubers after the foliage starts to fade in late summer or early spring. This arum is only suitable for United States Department of Agriculture zones 10 to 11 and will need to be overwintered indoors. Allow the tubers to dry out for a day and then store in a cool, dry location indoors until spring.