Photo: Greg HumeCC BY-SA 4.0via Wikimedia Commonsresized / cropped
Tall Ironweed Plant Care
Vernonia altissima Nutt.
Updated · Sources · How we source care data
Vernonia gigantea (also known as giant ironweed, tall ironweed or ironweed) is a species of perennial plant from family Asteraceae found in United States and Canada. The plant is native to the eastern United States, north to New York state and Ontario, and southwest to Texas.
Every 7–10 days
Full sun to partial shade
60–80°F
40–70%
At a glance
How do you care for Tall Ironweed?
Water Tall Ironweed every 7–10 days, letting the top layer of soil dry out between waterings, and give it full sun to partial shade. It prefers temperatures of 60–80°F (16–27°C) and 40–70% humidity. Fertilize it every 6 months during the growing season.
Where Is the Tall Ironweed Native To?
What Is the Tall Ironweed?
Tall Ironweed (Vernonia altissima) belongs to the Asteraceae family within the Vernonia genus. Tall Ironweed is native to the eastern United States, north to New York state and Ontario, and southwest to Texas. Tall Ironweed is also known as Tall Vernonia, Cacalia gigantea, Chrysocoma gigantea.
Tall Ironweed displays an upright, bushy perennial growth habit, reaching up to 3 ft tall with a spread of approximately 2 ft. Tall Ironweed produces small purple composite flowers in clusters.
Leaf size: approximately 6 inches.
How Often Should You Water a Tall Ironweed?
Vernonia altissima requires watering every 7–10 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 7–10 days
Let soil partially dry between waterings
What Light Does the Tall Ironweed Need?
Tall Ironweed thrives in full sun to partial shade.
Light Requirement
Full sun to partial shade
What Temperature and Humidity Does the Tall Ironweed Prefer?
Vernonia altissima grows best at temperatures of 60–80°F. Tall Ironweed prefers humidity levels of 40–70%.
Temperature
60–80°F
Humidity
40–70%
What Soil Mix Works Best for a Tall Ironweed?
Well-draining loamy soil with added compost for nutrients. Good drainage is essential for Tall Ironweed to prevent waterlogging, which leads to root rot and fungal issues.
How Often Should You Fertilize a Tall Ironweed?
Feed Tall Ironweed 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 Tall Ironweed?
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 Tall Ironweed?
Tall Ironweed can be propagated through seeds, division of root ball. Similar propagation techniques also apply to narrowleaf ironweed plant care, which shares the same genus.
Is the Tall Ironweed Toxic to Pets and Children?
Pet safety not verified
The ASPCA does not list Tall Ironweed, 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 Tall Ironweed?
Tall Ironweed is susceptible to aphids, spider mites, whiteflies. 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 Tall Ironweed Need?
Tall Ironweed grows outdoors in USDA Zone 5a – 9b. It survives winters down to planting zone 5a. Tall Ironweed is native to the eastern United States, north to New York state and Ontario, and southwest to Texas.
Hardiness Zone
Zone 5a – 9b
Keep exploring plants
Tall Ironweed 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 Vernonia genus — compare its care with other Vernonia species on PlantoScan.
Vernonia is part of the Asteraceae plant family — browse all Asteraceae genera and species.
Tall Ironweed thrives in bright light and direct sun — see other bright-light plants.
More Vernonia Species
Other Vernonia species in PlantoScan's care catalogue share similar watering, light, and soil preferences:
Sources
- Scientific name & taxonomy: Vernonia altissima Nutt., family Asteraceae (first published in Gen. N. Amer. Pl. 2: 134 (1818)) — World Flora Online record, IPNI name record.
- Pet toxicity: Pet safety not verified: the ASPCA does not list Tall Ironweed, 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: Greg Hume, CC BY-SA 4.0, Wikimedia Commons — original.
- Hardiness zone: USDA Zone 5a – 9b, 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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