Yellow Flag Plant Care

Yellow Flag (Iris pseudacorus) belongs to the Iridaceae family within the Iris genus. Yellow Flag is native to Europe, western Asia and northwest Africa. Yellow Flag is also known as Yellow Iris, Water Flag, Pale Yellow Iris.

Yellow Flag displays an upright, clumping perennial growth habit, reaching up to 2 ft tall with a spread of approximately 1 ft. Yellow Flag produces showy, colorful blooms with intricate patterns.

Leaf size: approximately 12 inches.

Iris pseudacorus 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.

Yellow Flag thrives in full sun to part shade.

Iris pseudacorus grows best at temperatures of 50–80°F. Yellow Flag prefers humidity levels of 40–70%.

Well-draining sandy loam with added compost for nutrients. Good drainage is essential for Yellow Flag to prevent waterlogging, which leads to root rot and fungal issues.

Feed Yellow Flag 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.

The PlantoScan app can remind you when to water and when to fertilize each plant.

Divide and repot every 3-4 years in late summer. Choose a pot one size larger than the current container, and ensure it has drainage holes to allow excess water to escape.

Yellow Flag can be propagated through division of rhizomes, seeds. Similar propagation techniques also apply to japanese iris plant care, which shares the same genus.

See all plants toxic to cats and plants toxic to dogs.

Yellow Flag is susceptible to aphids, iris borers, thrips. 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.

Yellow Flag grows outdoors in USDA Zone 4a – 9b. It survives winters down to planting zone 4a. Yellow Flag is native to Europe, western Asia and northwest Africa.