Photo: Oceancetaceen - Alice ChoduraPublic domainvia Wikimedia Commons
Cotton Thistle Plant Care
Onopordum tauricum Willd.
Updated · Sources · How we source care data
Onopordum tauricum, the Taurian thistle or bull cottonthistle, is a species of thistle. It is native to Eurasia and is known in Australia and the western United States as an introduced species. It easily becomes a noxious weed, similar to its relative, Onopordum acanthium.
Every 10–14 days
Full sun
50–80°F
40–60%
At a glance
How do you care for Cotton Thistle?
Water Cotton Thistle every 10–14 days, letting the top layer of soil dry out between waterings, and give it full sun. It prefers temperatures of 50–80°F (10–27°C) and 40–60% humidity. Fertilize it every 8 months during the growing season.
What Is the Cotton Thistle?
Cotton Thistle (Onopordum tauricum) belongs to the Asteraceae family within the Onopordum genus. Cotton Thistle is native to Eurasia. Cotton Thistle is also known as Taurian Scotch Thistle, Bull Thistle, Onopordum argolicum.
Cotton Thistle displays a tall, spiky biennial growth habit, reaching up to 6 ft tall with a spread of approximately 2 ft. Cotton Thistle produces large purple thistle-like flowers.
Leaf size: approximately 12 inches.
How Often Should You Water a Cotton Thistle?
Onopordum tauricum requires watering every 10–14 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 10–14 days
Let soil partially dry between waterings
What Light Does the Cotton Thistle Need?
Cotton Thistle thrives in full sun.
Light Requirement
Full sun
What Temperature and Humidity Does the Cotton Thistle Prefer?
Onopordum tauricum grows best at temperatures of 50–80°F. Cotton Thistle prefers humidity levels of 40–60%.
Temperature
50–80°F
Humidity
40–60%
What Soil Mix Works Best for a Cotton Thistle?
Well-draining sandy soil with good aeration. Good drainage is essential for Cotton Thistle to prevent waterlogging, which leads to root rot and fungal issues.
How Often Should You Fertilize a Cotton Thistle?
Feed Cotton Thistle every 8 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 8 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 Cotton Thistle?
Repot every 1-2 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 Cotton Thistle?
Cotton Thistle can be propagated through seeds. Similar propagation techniques also apply to onopordum × brevicaule plant care, which shares the same genus.
Is the Cotton Thistle Toxic to Pets and Children?
Pet safety not verified
The ASPCA does not list Cotton 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 Cotton Thistle?
Cotton Thistle is susceptible to aphids, caterpillars. 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 Cotton Thistle Need?
Cotton Thistle grows outdoors in USDA Zone 12a. It survives winters down to planting zone 12a. Cotton Thistle is native to Eurasia. In cooler regions, grow Cotton Thistle as a houseplant or bring it indoors before the first frost.
Hardiness Zone
Zone 12a
Keep exploring plants
Cotton 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 Onopordum genus — compare its care with other Onopordum species on PlantoScan.
Onopordum is part of the Asteraceae plant family — browse all Asteraceae genera and species.
Cotton Thistle thrives in bright light and direct sun — see other bright-light plants.
Related Plant Care Guides
Closely related plants with similar care requirements:
Sources
- Scientific name & taxonomy: Onopordum tauricum Willd., family Asteraceae (first published in Sp. Pl., ed. 4 , 3: 1687 (1803)) — World Flora Online record, IPNI name record.
- Pet toxicity: Pet safety not verified: the ASPCA does not list Cotton 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: Oceancetaceen - Alice Chodura, Public domain, 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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