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Blue boneset

Conoclinium coelestinum · Asteraceae

The gardener's calendar

The right move for September

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

JFMAMJJASOND Planting

ID card

Scientific name
Conoclinium coelestinum
Family
Asteraceae
Type
Perennial herbaceous plant
Flowering
August to October
Flower color
Sky blue to pale violet
Adult size
60 to 90 cm in height
Hardiness
-10 to -15 °C
Origin
Central and North America

Care

Light Exposure

Place your mistflower in full sun or partial shade for optimal flowering. It tolerates partial shade, but will flower more generously in a sunny location. Avoid overly shaded spots that would reduce flower production.

Watering

Keep the soil regularly moist, especially during growth and flowering. Water deeply once or twice a week depending on climate conditions. Reduce watering in winter after the plant goes dormant.

Soil

This plant prefers fertile, well-draining soil rich in organic matter. Amend the soil with compost or potting soil before planting. It tolerates slightly acidic to neutral soils.

Fertilizing

Apply a balanced fertilizer in spring when vegetative growth resumes. A second application in early summer supports abundant flowering. A slow-release fertilizer works particularly well.

Pruning and Cleaning

Pinch back young stems in spring to encourage branching and a more compact shape. Remove spent flowers regularly to extend blooming. Cut the plant back to ground level in fall or early spring.

Health and Diseases

Mistflower is generally robust. Watch for powdery mildew in case of excessive humidity and poor air circulation. Regular, well-spaced watering limits fungal problems. Few significant insect attacks.

Did you know?

Mistflower was historically called 'fleabane' in English because it was once hung in homes to repel fleas and other parasites. Its Latin name 'Conoclinium' comes from Greek and literally means 'united cone,' referring to the structure of its flower. It is highly appreciated by butterflies and pollinators in late summer.

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.