Cup plant Silphium perfoliatum
Cup plant (Silphium perfoliatum) is a deciduous perennial flowering plant in the Asteraceae family, native to Moist prairies and river edges of eastern and central North America. It grows 1.5–2.5 m (4.9–8.2 ft) tall and 80 cm–1.2 m (31 in–3.9 ft) wide, wants full sun and high water, and is hardy to about -35 °C (-31 °F). Space plants about 1 m (3.3 ft) apart.
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Cup plant at a glance
| Type | Perennial flowering plant, deciduous |
|---|---|
| Family | Asteraceae |
| Mature height | 1.5–2.5 m (4.9–8.2 ft) |
| Mature spread | 80 cm–1.2 m (31 in–3.9 ft) |
| Spacing | 1 m (3.3 ft) centre to centre |
| Sun | Full sun, at least 6 h of direct sun a day |
| Water | High; drought tolerance moderate, waterlogging tolerance moderate |
| Soil pH | 5.5–8 |
| Cold hardiness | About -35 °C (-31 °F) once established (roughly USDA zone 3) |
| Heat stress | Likely above about 36 °C (97 °F) |
| Flowering | from about July for 7–10 weeks (northern hemisphere; later in cold climates, earlier in warm ones) |
| Wind tolerance | Low |
| Pollinator value | High |
| Edible | Not grown as food |
| Native to | Moist prairies and river edges of eastern and central North America |
| Common in gardens of | 🇺🇸 United States, 🇨🇦 Canada, 🇩🇪 Germany, 🇵🇱 Poland |
| Invasive in | parts of central Europe and China (where grown as a bioenergy crop): check local rules before planting |
Is Cup plant toxic?
- People: not known to be toxic
- Cats: not known to be toxic
- Dogs: not known to be toxic
Not known to be poisonous.
If a child or pet may have eaten part of a plant, call a poison centre or vet straight away.
Companion planting: what to grow with Cup plant
No well-documented helpful pairing. Group it with plants that like full sun and high water.
Questions about Cup plant
- How far apart should I plant Cup plant?
- About 1 m (3.3 ft) apart, centre to centre. A mature plant spreads 80 cm–1.2 m (31 in–3.9 ft).
- Does Cup plant need full sun?
- Full sun: at least 6 hours of direct sun a day.
- How much water does Cup plant need?
- High water. Drought tolerance is moderate and waterlogging tolerance moderate.
- How cold-hardy is Cup plant?
- It tolerates about -35 °C (-31 °F) once established, roughly USDA zone 3.
- When does Cup plant flower?
- From about July for 7–10 weeks (northern hemisphere; later in cold climates, earlier in warm ones).
- Is Cup plant poisonous to cats and dogs?
- For cats it is not known to be toxic; for dogs not known to be toxic; for people not known to be toxic. Not known to be poisonous.
- What grows well with Cup plant?
- There is no well-documented companion pairing for Cup plant. Group it with plants that like the same sun (full sun) and water (high).
Sources and evidence
Evidence grade A (A: strong evidence).
- Plants of the World Online (taxonomy, native range), Royal Botanic Gardens, Kew
- Missouri Botanical Garden Plant Finder, Missouri Botanical Garden
- CABI Invasive Species Compendium, CABI
Notes and assumptions
- Square stems pierce through pairs of joined leaves that form cups holding rainwater, where goldfinches, butterflies and bees drink; masses of yellow daisies follow in late summer. Self-seeds freely. In Germany it is grown as a biogas crop that also feeds bees.
Reference values for planning, not horticultural, veterinary or medical advice. Varieties, soils and local climates differ: check with a local nursery or extension service.
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- Zinnia Zinnia elegans
- Cosmos Cosmos bipinnatus
- Purple coneflower Echinacea purpurea
- Black-eyed Susan Rudbeckia hirta
- French tarragon Artemisia dracunculus