Photo: Oleg KosterinCC BY 4.0via iNaturalistresized / cropped
Red Onion Plant Care
Allium atrosanguineum Schrenk
Updated · Sources · How we source care data
This plant's striking deep purple flowers are its most distinctive visual feature, contrasting beautifully against its bright green foliage. Originating from the Caucasus region, Allium atrosanguineum is highly sought after by plant collectors for its unique coloration and ability to attract pollinators to the garden.
Every 7–14 days
Full sun to partial shade
50–75°F
40–60%
At a glance
How do you care for Red Onion?
Water Red Onion 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 50–75°F (10–24°C) and 40–60% humidity. Fertilize it every 6 months during the growing season. It is reported as toxic to pets, so keep it out of reach of pets.
Where Is the Red Onion Native To?
What Is the Red Onion?
Red Onion (Allium atrosanguineum) belongs to the Amaryllidaceae family within the Allium genus. Red Onion is native to China, Siberia, Mongolia, and Central Asia.
Red Onion displays an upright, clumping perennial growth habit, reaching up to 2 ft tall with a spread of approximately 0.5 ft. Red Onion produces spherical clusters of small purple, white, or pink flowers.
Leaf size: approximately 12 inches.
How Often Should You Water a Red Onion?
Allium atrosanguineum 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 Red Onion Need?
Red Onion thrives in full sun to partial shade.
Light Requirement
Full sun to partial shade
What Temperature and Humidity Does the Red Onion Prefer?
Allium atrosanguineum grows best at temperatures of 50–75°F. Red Onion prefers humidity levels of 40–60%.
Temperature
50–75°F
Humidity
40–60%
What Soil Mix Works Best for a Red Onion?
Well-draining sandy loam with added compost for nutrients. Good drainage is essential for Red Onion to prevent waterlogging, which leads to root rot and fungal issues.
How Often Should You Fertilize a Red Onion?
Feed Red Onion 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 Red Onion?
Divide and repot every 3-4 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 Red Onion?
Red Onion can be propagated through division of bulbs, offsets, seeds. Similar propagation techniques also apply to onion plant care, which shares the same genus.
Is the Red Onion Toxic to Pets and Children?
Toxic (caution)
Reported as toxic in our plant data. Not verified by the ASPCA.
Toxic to dogs, cats, and horses if ingested
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 Red Onion?
Red Onion is susceptible to onion thrips, onion maggots. 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 Red Onion Need?
Red Onion grows outdoors in USDA Zone 4a – 8b. It survives winters down to planting zone 4a. Red Onion is native to China, Siberia, Mongolia, and Central Asia.
Hardiness Zone
Zone 4a – 8b
Keep exploring plants
Red Onion 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 Allium genus — compare its care with other Allium species on PlantoScan.
Allium is part of the Amaryllidaceae plant family — browse all Amaryllidaceae genera and species.
Red Onion thrives in bright light and direct sun — see other bright-light plants.
More Allium Species
Other Allium species in PlantoScan's care catalogue share similar watering, light, and soil preferences:
Sources
- Scientific name & taxonomy: Allium atrosanguineum Schrenk, family Amaryllidaceae (first published in Bull. Sci. Acad. Imp. Sci. Saint-Pétersbourg 10: 355 (1842)) — World Flora Online record, IPNI name record.
- Pet toxicity: Red Onion is reported as toxic to pets in our plant data (not verified by the ASPCA), so treat it with caution. Checked against the ASPCA plant list; any other toxicity note on this page comes from PlantoScan's plant database.
- Photo: Oleg Kosterin, CC BY 4.0, iNaturalist — original.
- Hardiness zone: USDA Zone 4a – 8b, estimated from the plant's typical growing conditions.
- 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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