Yellow starthistle
Centaurea solstitialis · Asteraceae
The gardener's calendar
Ideal time to plant yellow starthistle: set it out when the soil is neither frozen nor waterlogged, and water generously as it establishes.
ID card
- Foliage
- Deciduous
- Flowering
- June to September (summer solstice)
- Adult size
- 60 to 100 cm tall
- Growth
- Fast
- Hardiness
- Very hardy (down to -15°C)
- Origin
- Mediterranean basin
- Soil type
- Well-drained, rather dry, calcareous
- Exposure
- Full sun
Care
Exposure
Place your solstice centaury in full sun, as it loves direct light and flowers more abundantly in these conditions. At least 6 to 8 hours of daily sunlight ensures generous flowering and intense colors.
Watering
Once established, this plant is very drought-resistant and requires little watering. Water moderately during the growth phase, then reduce considerably after establishment. Avoid standing moisture that could promote root rot.
Soil
Prefer well-drained, dry and calcareous soil, or slightly gravelly soil. Poor soil works better than overly rich soil, which would encourage foliage at the expense of flowering. Improve drainage by adding sand or gravel if needed.
Pruning and deadheading
Pinch young plants in spring to encourage a bushy, dense habit. At the end of the season, you can leave spent flowers to allow self-seeding, or cut them off to extend flowering. Cut back the plant in spring if it becomes too invasive.
Fertilizer
This plant is not nutrient-demanding. Light fertilization in spring is more than enough. Avoid overly rich fertilizers that would slow flowering; if possible, use a balanced formula or one slightly deficient in nitrogen.
Diseases and pests
Solstice centaury is generally very robust. It can be affected by powdery mildew in humid conditions (encourage air circulation), or by rare aphid attacks. A well-drained and airy environment prevents most health problems.
Did you know?
The solstice centaury gets its scientific name 'solstitialis' from its flowering which peaks at the summer solstice. Native to the Mediterranean basin, it has naturalized in many arid regions of the world and is considered an indicator plant of degraded or overgrazed areas.
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.