Cobra lily is one of the most architectural shade plants available: a tall, slender spathe striped in green and purple rises above a whorl of radiating leaflets like a cobra about to strike. The flower (a spadix inside the spathe) is strange rather than pretty, and it is followed in autumn by a club of red berries. It reaches 18 to 36 inches.
It is a woodland plant from the Himalayas and western China, and it wants what a woodland gives: part to full shade, humus-rich soil that holds moisture but drains, and steady water while it is growing. Plant the tubers 4 to 6 inches deep in spring or fall, 12 to 18 inches apart, and mark the spot, because it comes up late, often not until early summer, and is easy to spear with a trowel. Mulch over winter in zone 5 and 6.
All parts are toxic if eaten, which is why deer and rodents leave it alone. The berries are eaten by birds, which is how it spreads in the wild. Plant it where its form can be seen up close, among ferns, hostas and epimediums, and leave it undisturbed; a settled tuber gets larger and more dramatic each year.
Crown Rot
Lower leaves yellow and wilt; the base of the rosette turns brown and soft, sometimes with white fungal threads at the soil line. Plants collapse in wet conditions.
Remove and destroy affected plants. Improve drainage and avoid overhead watering. Do not mulch directly against the crown. Space plants for airflow and avoid replanting in the same wet spot.
Rust
Orange to brown raised pustules on the undersides of leaves, with yellow spotting on the upper surface. Heavy infections cause leaves to yellow and drop.
Remove and destroy infected leaves. Avoid overhead watering and improve air circulation. Apply a sulfur or copper-based fungicide if it spreads. Clear plant debris in fall.