Photo: PhilmarinCC BY-SA 3.0via Wikimedia Commonsresized / cropped
Common Star-thistle Plant Care
Centaurea calcitrapa M.Bieb.
Updated · Sources · How we source care data
Centaurea calcitrapa is a species of flowering plant known by several common names, including red star-thistle and purple starthistle. It is native to Europe but is rarely found there, it is known across the globe as an introduced species and often a noxious weed. The species name calcitrapa comes from the word caltrop, a type of weapon covered in sharp spikes.
Every 7–14 days
Full sun to partial shade
50–80°F
40–70%
At a glance
How do you care for Common Star-thistle?
Water Common Star-thistle every 7–14 days, letting the top layer of soil dry out between waterings, and give it full sun to partial shade. It prefers temperatures of 50–80°F (10–27°C) and 40–70% humidity. Fertilize it every 6 months during the growing season.
Where Is the Common Star-thistle Native To?
- Albania
- Austria
- Belarus
- Belgium
- Bosnia and Herzegovina
- Bulgaria
- Croatia
- Cyprus
- Czechia
- Denmark
- Estonia
- Finland
- France
- Germany
- Greece
- Hungary
- Iceland
- Ireland
- Italy
- Latvia
- Lithuania
- Luxembourg
- Malta
- Moldova
- Montenegro
- North Macedonia
- Norway
- Poland
- Portugal
- Romania
- Russia
- Serbia
- Slovakia
- Slovenia
- Spain
- Sweden
- Switzerland
- The Netherlands
- Ukraine
- United Kingdom
What Is the Common Star-thistle?
Common Star-thistle (Centaurea calcitrapa) belongs to the Asteraceae family within the Centaurea genus. Common Star-thistle is native to Europe. Common Star-thistle is also known as Star-thistle, Purple Star-thistle, St. Barnaby's Thistle.
Common Star-thistle displays an upright, branching perennial growth habit, reaching up to 3 ft tall with a spread of approximately 2 ft. Common Star-thistle produces showy, thistle-like flower heads in various colors.
Leaf size: approximately 6 inches.
How Often Should You Water a Common Star-thistle?
Centaurea calcitrapa requires watering every 7–14 days. Allow the top layer of soil to dry between waterings to prevent root rot. Reduce watering frequency during winter when growth slows.
Watering Frequency
Every 7–14 days
Let soil partially dry between waterings
What Light Does the Common Star-thistle Need?
Common Star-thistle thrives in full sun to partial shade.
Light Requirement
Full sun to partial shade
What Temperature and Humidity Does the Common Star-thistle Prefer?
Centaurea calcitrapa grows best at temperatures of 50–80°F. Common Star-thistle prefers humidity levels of 40–70%.
Temperature
50–80°F
Humidity
40–70%
What Soil Mix Works Best for a Common Star-thistle?
Well-draining sandy loam with added organic matter for moisture retention. Good drainage is essential for Common Star-thistle to prevent waterlogging, which leads to root rot and fungal issues.
How Often Should You Fertilize a Common Star-thistle?
Feed Common Star-thistle every 6 months during the growing season (spring and summer) with a balanced fertilizer diluted to the strength on the label.
Pause feeding in autumn and winter, when growth slows, and never fertilize dry soil — water first.
Fertilizing
Every 6 months
During the growing season
The PlantoScan app can remind you when to water and when to fertilize each plant.
How Do You Repot a Common Star-thistle?
Repot every 2-3 years in early spring. Choose a pot one size larger than the current container, and ensure it has drainage holes to allow excess water to escape.
How Do You Propagate a Common Star-thistle?
Common Star-thistle can be propagated through seeds, division of clumps. Similar propagation techniques also apply to blue cornflower plant care, which shares the same genus.
Is the Common Star-thistle Toxic to Pets and Children?
Pet safety not verified
The ASPCA does not list Common Star-thistle, so we can't confirm whether it is safe for cats and dogs. Keep pets from chewing it as a precaution.
This is a general caution, not veterinary or medical advice. If your pet ate a plant, contact your vet or animal poison control.
See all plants toxic to cats and plants toxic to dogs.
What Pests and Diseases Affect the Common Star-thistle?
Common Star-thistle is susceptible to aphids, spider mites, powdery mildew. Inspect the foliage regularly, especially along leaf undersides and stems. Treat infestations promptly with insecticidal soap or neem oil to prevent spread.
Yellow leaves, brown tips or drooping? See common plant problems and how to fix them.
What USDA Hardiness Zone Does the Common Star-thistle Need?
Common Star-thistle grows outdoors in USDA Zone 12a. It survives winters down to planting zone 12a. Common Star-thistle is native to Europe. In cooler regions, grow Common Star-thistle as a houseplant or bring it indoors before the first frost.
Hardiness Zone
Zone 12a
Keep exploring plants
Common Star-thistle is one of many species covered in the complete plant care and identification guide, which groups plants by genus, attribute, and popularity.
It belongs to the Centaurea genus — compare its care with other Centaurea species on PlantoScan.
Centaurea is part of the Asteraceae plant family — browse all Asteraceae genera and species.
Common Star-thistle thrives in bright light and direct sun — see other bright-light plants.
More Centaurea Species
Other Centaurea species in PlantoScan's care catalogue share similar watering, light, and soil preferences:
Sources
- Scientific name & taxonomy: Centaurea calcitrapa M.Bieb., family Asteraceae (first published in Fl. Taur.-Caucas. 3: 594 (Dec 1819 or early 182) — World Flora Online record, IPNI name record.
- Pet toxicity: Pet safety not verified: the ASPCA does not list Common Star-thistle, so we can't confirm whether it is safe for cats and dogs. Checked against the ASPCA plant list; any other toxicity note on this page comes from PlantoScan's plant database.
- Photo: Philmarin, CC BY-SA 3.0, Wikimedia Commons — original.
- Hardiness zone: USDA Zone 12a, calculated from the plant's minimum temperature.
- Care values(watering, light, temperature, humidity, soil, fertilizing): PlantoScan's plant database, filtered by automatic plausibility checks — values that fail them are hidden. How we source and check plant data.
Spotted a mistake? Email info@upvision.media with the page link — we check and correct reported errors.
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