Tall boneset
Ageratina altissima · Asteraceae
The gardener's calendar
Ideal time to plant tall boneset: set it out when the soil is neither frozen nor waterlogged, and water generously as it establishes.
ID card
- Foliage
- Deciduous
- Flowering
- August to October
- Mature size
- 1 to 1.5 m tall
- Growth rate
- Fast
- Hardiness
- Zone 5 to 9 (minimum –15 °C)
- Origin
- North America
- Soil type
- Well-drained, tolerant
Care
Watering
Water regularly during the growing season, especially in dry spells. Once established, the plant tolerates dry conditions better. Avoid waterlogging, which promotes fungal diseases.
Light exposure
Choose a sunny or partially shaded location. The plant tolerates part shade well but will flower more abundantly in full sun. It adapts well to semi-natural spaces and sheltered areas.
Pruning and cutting
Cut the plant back in late winter or early spring to encourage dense, compact growth. Remove faded flowers to extend the flowering period. This pruning rejuvenates the clump and limits self-seeding.
Soil
Eupatorium tolerates a wide range of soils, from sandy to silty, as long as they are not constantly waterlogged. Rich soil improves overall vigor. Improve poor soils with well-decomposed compost when planting.
Fertilizer
Apply a balanced fertilizer in spring when growth resumes. In rich soil, fertilizing can be reduced to avoid a loose habit. Moderate feeding is sufficient to maintain good flowering.
Diseases and pests
The plant is generally hardy against pests. Watch for powdery mildew in humid, shaded conditions: improve air circulation and avoid wetting the foliage. Excess moisture can promote root rot.
Did you know?
Soft-leaved eupatorium bears the genus name Ageratina in reference to Ageratum (meaning 'without age' in Greek), alluding to the longevity of its flowers. Formerly, plants of this genus were used in traditional medicine by North American indigenous peoples, though their exact properties remain poorly documented.
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.
Add this plant to my garden →Plants from the same family
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Tips generated and checked by Viridia — adapt them to your local climate.