QuestionsHow to growFlowersBorder Perennial Flowerstrilliums 0 Vote Up Vote Down Joseph Bates asked 15 years ago Just would like to enquire about planting trilliums, i have got some rhizomes as gifts, but was unsure on how to plant them,do you plant them like bearded iris lengthways,or do you plant them like a bulb? 1 Answers 0 Vote Up Vote Down Gerry Daly Staff answered 6 years ago The rhizome of trillium will grow more or less horizontal, so you can plant horizontal. Use lots of leaf-mould dug when planting.Â