That appears to be Scadoxus membranaceus, a bulbous plant from South Africa. Yours has a longer leaf stalk than I am used to seeing. Here's a comparison pic:
They require a temperature over 40 degrees Fahrenheit at all times. It should be planted in highly organic, well drained soil, and watered regularly during the summer, and kept moderately dry during winter. Try not to disturb the bulb once planted. If a leaf or flower stall shrivels, it can be removed.