Photo: Greg HumeCC BY-SA 4.0via Wikimedia Commonsresized / cropped
Giant Ironweed Plant Care
Vernonia gigantea (Walter) Trel.
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 Giant Ironweed?
Water Giant 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 Giant Ironweed Native To?
What Is the Giant Ironweed?
Giant Ironweed (Vernonia gigantea) belongs to the Asteraceae family within the Vernonia genus. Giant Ironweed is native to the eastern United States, north to New York state and Ontario, and southwest to Texas. Giant Ironweed is also known as Tall Ironweed, Ironweed, Cacalia gigantea.
Giant Ironweed displays an upright, bushy perennial growth habit, reaching up to 3 ft tall with a spread of approximately 2 ft. Giant Ironweed produces small purple composite flowers in clusters.
Leaf size: approximately 6 inches.
How Often Should You Water a Giant Ironweed?
Vernonia gigantea 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 Giant Ironweed Need?
Giant Ironweed thrives in full sun to partial shade.
Light Requirement
Full sun to partial shade
What Temperature and Humidity Does the Giant Ironweed Prefer?
Vernonia gigantea grows best at temperatures of 60–80°F. Giant Ironweed prefers humidity levels of 40–70%.
Temperature
60–80°F
Humidity
40–70%
What Soil Mix Works Best for a Giant Ironweed?
Well-draining loamy soil with added compost for nutrients. Good drainage is essential for Giant Ironweed to prevent waterlogging, which leads to root rot and fungal issues.
How Often Should You Fertilize a Giant Ironweed?
Feed Giant 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 Giant 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 Giant Ironweed?
Giant 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 Giant Ironweed Toxic to Pets and Children?
Pet safety not verified
The ASPCA does not list Giant 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 Giant Ironweed?
Giant 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 Giant Ironweed Need?
Giant Ironweed grows outdoors in USDA Zone 13a. It survives winters down to planting zone 13a. Giant Ironweed is native to the eastern United States, north to New York state and Ontario, and southwest to Texas. In cooler regions, grow Giant Ironweed as a houseplant or bring it indoors before the first frost.
Hardiness Zone
Zone 13a
Keep exploring plants
Giant 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.
Giant 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 gigantea (Walter) Trel., family Asteraceae (first published in Rep. (Annual) Arkansas Geol. Surv. 1888(4): 189 (1891)) — World Flora Online record, IPNI name record.
- Pet toxicity: Pet safety not verified: the ASPCA does not list Giant 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 13a, 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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