Japanese spikenard is one of the most dramatically scaled perennials you can grow in a shaded garden — the enormous compound leaves, each up to three feet across, create a bold, almost tropical effect in a woodland setting. It dies back completely to the ground each winter and emerges late in spring, then grows with remarkable speed to its full height by midsummer. Small creamy-white flowers are held in large branching umbels above the foliage in July and August, followed by dark purple berries that draw birds.
In Japan the young shoots are eaten as udo — harvested in early spring before they harden, blanched or eaten raw, with a flavour somewhere between asparagus and celery. The golden-leafed cultivar 'Sun King' has become popular in Western gardens for its chartreuse foliage that lights up shaded spots. Plant where the scale can be appreciated — it is too large for small gardens but genuinely spectacular in a border with ferns, hellebores, and hostas.
Aphids
Clusters of small soft insects on new growth and flower buds.
Knock off with a strong jet of water. Ladybirds and lacewings are natural predators. Insecticidal soap as last resort.
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.
Aralia Leaf Spot
Brown or purplish spots on leaves, often with yellow halos, spreading during warm humid weather. Heavy infection causes leaves to yellow and drop early.
Remove and destroy infected leaves. Avoid overhead watering and improve air circulation by thinning crowded stems. Clear fallen debris in fall to reduce overwintering spores.