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Cup plant

Silphium perfoliatum · Asteraceae

The gardener's calendar

The right move for September

Ideal time to plant cup plant: set it out when the soil is neither frozen nor waterlogged, and water generously as it establishes.

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ID card

Family
Asteraceae
Type
Perennial herb
Foliage
Deciduous
Flowering
July to September, yellow flowers
Mature size
1.5 to 2.5 m in height
Hardiness
Very hardy (down to -20 °C)
Origin
North America
Growth
Fast

Care

Sunlight

Cup plant prefers a sunny location (6 to 8 hours of direct sunlight daily) for optimal flowering. It also tolerates partial shade but develops better in full sun. Avoid overly shaded areas that would reduce flower production.

Soil

This plant adapts to many soil types but prefers well-drained, fertile soil. It tolerates dry soil once established, making it undemanding. Improving the soil with compost at planting time promotes better initial growth.

Watering

Water regularly during the first year of establishment to keep the soil moist. Once well-rooted, the plant tolerates drought and needs little watering. During active growth, weekly watering is sufficient unless there's prolonged drought.

Fertilizing

Cup plant is undemanding when it comes to fertilization. A compost application in spring is generally sufficient. Avoid nitrogen-rich fertilizers that would promote foliage at the expense of flowers.

Pruning and training

Cut stems to ground level in autumn or late winter after dormancy. Pinch young plants in spring to encourage bushier branching and better structure. Remove spent flowers to extend blooming.

Diseases and pests

Cup plant is generally very robust and rarely subject to disease. Occasionally check for aphids or powdery mildew if humidity is excessive, but infestations remain rare. Good drainage and air circulation are sufficient to prevent most problems.

Did you know?

Cup plant owes its scientific name 'perfoliatum' to its remarkable leaves: they are fused at the base around the stem, creating the impression that the stem passes through them like a perforation. This unique botanical characteristic, invisible at first glance, has fascinated naturalists for several centuries.

Where to buy it

Plant in spring or early autumn, avoiding spells of intense heat. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, April, May, September.

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Tips generated and checked by Viridia — adapt them to your local climate.