Photo: Walter SiegmundCC BY-SA 3.0via Wikimedia Commonsresized / cropped
Longest Agoseris Plant Care
Agoseris longissima Greene
Updated · Sources · How we source care data
This plant is easily distinguishable by its long, slender leaves that can reach up to 18 inches in length. Originating from the western United States, Agoseris longissima is highly sought after by plant collectors for its unique foliage and ability to add a striking vertical element to gardens and landscapes.
Every 7–14 days
Full sun to partial shade
65–75°F
40–60%
At a glance
How do you care for Longest Agoseris?
Water Longest Agoseris 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 65–75°F (18–24°C) and 40–60% humidity. Fertilize it every 2 months during the growing season.
Where Is the Longest Agoseris Native To?
What Is the Longest Agoseris?
Longest Agoseris (Agoseris longissima) belongs to the Asteraceae family within the Agoseris genus. Longest Agoseris is native to western North America. Longest Agoseris is also known as Longest False Dandelion, Agoseris lacera, Agoseris lapathifolia.
Longest Agoseris displays a low rosette, clumping growth habit, reaching up to 1 ft tall with a spread of approximately . Longest Agoseris produces bright yellow daisy-like flowers.
Leaf size: approximately 4 inches.
How Often Should You Water a Longest Agoseris?
Agoseris longissima 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 Longest Agoseris Need?
Longest Agoseris thrives in full sun to partial shade.
Light Requirement
Full sun to partial shade
What Temperature and Humidity Does the Longest Agoseris Prefer?
Agoseris longissima grows best at temperatures of 65–75°F. Longest Agoseris prefers humidity levels of 40–60%.
Temperature
65–75°F
Humidity
40–60%
What Soil Mix Works Best for a Longest Agoseris?
Well-draining sandy soil with some organic matter. Good drainage is essential for Longest Agoseris to prevent waterlogging, which leads to root rot and fungal issues.
How Often Should You Fertilize a Longest Agoseris?
Feed Longest Agoseris every 2 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 2 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 Longest Agoseris?
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 Longest Agoseris?
Longest Agoseris can be propagated through seeds, division of root clumps. Similar propagation techniques also apply to false dandelion plant care, which shares the same genus.
Is the Longest Agoseris Toxic to Pets and Children?
Pet safety not verified
The ASPCA does not list Longest Agoseris, 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 Longest Agoseris?
Longest Agoseris 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.
Keep exploring plants
Longest Agoseris 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 Agoseris genus — compare its care with other Agoseris species on PlantoScan.
Agoseris is part of the Asteraceae plant family — browse all Asteraceae genera and species.
Longest Agoseris 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: Agoseris longissima Greene, family Asteraceae (first published in Leafl. Bot. Observ. Crit. 2: 122 (1911)) — World Flora Online record, IPNI name record.
- Pet toxicity: Pet safety not verified: the ASPCA does not list Longest Agoseris, 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: Walter Siegmund, CC BY-SA 3.0, Wikimedia Commons — original.
- 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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