How to Grow Cup Plant
Silphium perfoliatum
Cup Plant is a towering prairie perennial reaching 2-3 m, with bold yellow daisy-like flowers in midsummer and distinctive perfoliate leaves that cup around the stem to collect rainwater, attracting birds and insects. Plant in full sun in any well-drained soil; it is drought-tolerant once established. Allow 90 cm between plants and stake in exposed sites. Cut back to ground level each autumn or spring. Divide every 3-4 years to keep clumps vigorous.
Yearly Lifecycle
Care Essentials
Little feeding needed. Top-dress with compost in spring. Avoid high-nitrogen feeds which promote lush, floppy growth.
Watch For
- Slugs on spring shoots
- Aphids on stems
- Powdery mildew in dry spells
Companions
Echinacea, Rudbeckia, Grasses, Joe Pye Weed
Care Requirements
Light
Full sun
Requires at least 6 hours of direct sun daily. Tolerates light afternoon shade but may become floppy. Best in open borders away from tall shade-casting structures.
Watering
Low once established
Water regularly during the first season to help establishment. Once mature, Cup Plant is highly drought-tolerant and rarely needs supplemental irrigation except in prolonged dry spells.
Fertilizing
Minimal feeding needed
Top-dress with compost in spring. Avoid high-nitrogen fertilizers as they cause lush, floppy growth. The plant thrives in average to poor soils without extra feeding.
Pruning
Cut to ground in autumn or spring
Remove all stems to ground level in late autumn or early spring. Deadheading after flowering is optional; leaving seed heads provides food for birds and allows self-seeding.
Spacing
90 cm apart
Allow 90 cm between plants to accommodate their spread. Plants form large clumps over time and will need dividing every 3-4 years to prevent congestion.
Support
May need staking in exposed sites
In sheltered gardens, Cup Plant usually stands without support. In windy or exposed positions, stake stems in late spring before they reach full height.
