Overview
Trachelium caeruleum 'Black Knight' is a bushy bedding in the genus Trachelium, part of the Campanulaceae family, with deciduous foliage. Trachelium caeruleum 'Black Knight' grows best in full sun, and tolerates loam and sand soils and any pH. Its UK hardiness is rated H2. Suggested uses include city and courtyard gardens, patio and container plants, cottage and informal garden, flower borders and beds, cut flowers and wall side borders.
About
A herbaceous perennial, Trachelium caeruleum 'Black Knight' forms an erect, woody-based plant that bears dense violet-purple flower clusters. It typically reaches about 1.2 m and is often grown as a half-hardy summer bedding subject in the UK. Plants are well-branched and produce blooms from July to September. Suitable for containers, borders and cut flowers.
About the genus
Trachelium is a genus of flowering plants in the family Campanulaceae. It includes two species and one natural hybrid native to Macaronesia and the western and central Mediterranean.
Wikipedia contributors, "Trachelium (plant)", CC BY-SA 4.0 — Trachelium (plant)
In the garden
Trachelium caeruleum 'Black Knight' is a woody-based, erect herbaceous perennial native to the Mediterranean and usually cultivated as a half-hardy summer subject in temperate gardens. In the UK it is commonly used for summer bedding and conservatory culture where its compact violet-purple clusters provide season-long interest. Mature plants can reach roughly 1.2 m tall by around 0.3 m wide. Position it in full sun in a loam or sandy soil that retains moisture yet drains freely; the species accepts acid, neutral or alkaline pH. Soil should be kept moist but well-drained rather than waterlogged. The plant is rated H2 (half-hardy), so in colder winters treat it as a half-hardy perennial — grown under glass or as an annual in exposed sites — and use east- or west-facing spots for best flowering. Use Trachelium caeruleum 'Black Knight' in city and courtyard gardens, patio containers, cottage or informal borders, wall-side borders and for cut flowers. It performs well in both sheltered and more exposed locations when given a sunny aspect and consistent moisture. Flowers appear from July to September and suit cutting for summer displays.
Growing conditions
Best soil and position for Trachelium
- Sunlight
- Full sun
- Soil type
- Loam, Sand
- Soil pH
- Acid, Alkaline, Neutral
- Soil moisture
- Moist but well-drained
- Aspect
- West-facing, East-facing
- Exposure
- Exposed, Sheltered
- UK hardiness
- H2
Plant details
Trachelium caeruleum 'Black Knight' size, habit and characteristics
- Plant type
- Bedding, Conservatory Greenhouse, Herbaceous Perennial, Annual Biennial
- Habit
- Bushy
- Foliage
- Deciduous
- Suggested uses
- City and courtyard gardens, Patio and container plants, Cottage and informal garden, Flower borders and beds, Cut flowers, Wall side borders
Care notes
Pruning and caring for Trachelium caeruleum 'Black Knight'
- Propagation
- Seed sown at 16°C in spring
- Pest resistance
- Generally pest-free
- Disease resistance
- Generally disease-free
Frequently asked questions
Where is the best place to plant Trachelium caeruleum 'Black Knight'?
Trachelium caeruleum 'Black Knight' prefers full sun. It suits exposed and sheltered positions.
What soil does Trachelium caeruleum 'Black Knight' need?
Trachelium caeruleum 'Black Knight' grows best in loam and sand soil. It is happy in soil of any pH. Aim for soil that stays moist but well-drained.
Is Trachelium caeruleum 'Black Knight' hardy in the UK?
Trachelium caeruleum 'Black Knight' has an RHS hardiness rating of H2, meaning it is tender, tolerating 1–5°C, and needs frost-free protection over winter.
How do I propagate Trachelium caeruleum 'Black Knight'?
Seed sown at 16°C in spring.