How to Grow Scotch Thistle
Onopordum acanthium
Scotch Thistle is a hardy biennial — sow seed in late spring or early summer, let it form a large silver-woolly rosette in year one, then enjoy towering 2–3 m branching stems with purple thistle flowers in year two. Sow direct on well-drained, open ground in full sun; thin to 90 cm apart. No feeding needed on average soil. Drought-tolerant once established. Deadhead most spent heads to control spread, but leave a few to self-seed for a continuous succession. Wear gloves — all parts are spiny.
In your Leaftide garden - Hardiness
- Hardy
- Season
- Any Season
- Harvest
- Continuous Harvest
- Spacing
- 90 cm
- Height
- 250 cm
- Sow depth
- 1 cm
- Min. soil temperature
- 5°C+
- Start from
- Seed
- Light
- Full sun
- Water
- Low
When to Start
Sow from late spring to midsummer, in trays or where it is to flower. It only grows leaves in its first year and flowers the following spring or summer.
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Growth Stages
Approximate days from start
Care Essentials
- Onopordum is a lean feeder — no feeding is needed on average garden soil. On very poor or sandy soils, a single light balanced dressing at transplanting encourages strong first-year rosettes.
- A dramatic architectural biennial reaching 2–3 m in its second year, with huge silver-white woolly leaves and wings running up the branching stems. Purple thistle flower heads appear from midsummer. Hardy and drought-tolerant once established; self-seeds freely on bare or disturbed soil. Superb at the back of a border or as a specimen. Gloves recommended — all parts are spiny.
Growing Conditions
- Min. soil temperature
- 5°C+
- Germination temperature
- 10–20°C
- When to Start
- Sow from late spring to midsummer, in trays or where it is to flower. It only grows leaves in its first year and flowers the following spring or summer.
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Spacing & Planting
| Plant spacing | 90 cm |
| Row spacing | 100 cm |
| Sow depth | 1 cm |
| Mature height | 250 cm |
| Mature spread | 90 cm |
Growing Conditions
| Min. soil temperature | 5°C |
| Germination temperature | 10–20°C |
| Base growth temperature | 4°C |
| Min. daylength to start | 10h |
| Photoperiod sensitivity | day neutral |
Frequently Asked Questions
- How far apart should I plant Scotch Thistle?
- Plant Scotch Thistle 90cm apart with 100cm between rows.
- When does Scotch Thistle flower?
- Scotch Thistle flowers the year after sowing. It spends its first year growing leaves and flowers the following spring or summer.
- Is Scotch Thistle frost hardy?
- Scotch Thistle is classified as Hardy.