Yellow Flag

Iris pseudacorus

aquatic

Yellow Flag is a vigorous, tall iris species bearing striking golden-yellow flowers with darker veining and sword-shaped leaves reaching 3–5 feet in height. It thrives in shallow water, pond margins, and wetlands, spreading via thick, spreading rhizomes. While ornamentally valuable, it is highly invasive in some regions and requires containment.

Common Problems

Select the problem your Yellow Flag is experiencing to get a treatment guide.

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Slow Growthchevron_right

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Pale Leaveschevron_right

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Underwateringchevron_right

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Root Rotchevron_right

Care Guide

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Light

Full sun to partial shade; requires 5+ hours of direct sunlight; blooms best with abundant light

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Water

Shallow water (2–6 inches/5–15 cm depth) or wet bog soil; tolerates dry soils but prefers consistent moisture; hardy in standing water

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Soil

Rich, organic-matter-dense soil or aquatic sediment; tolerates poor, clayey substrates; neutral to slightly acidic pH optimal

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Fertiliser

Low to moderate fertilizer; thrives in nutrient-rich water or soil amended with compost; excess nitrogen promotes foliage over flowers

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Temperature

Very hardy; tolerates cold to 30°F (-1°C); dormant in winter; optimal growth 50–75°F (10–24°C)

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Humidity

Requires high moisture; not suitable for drought conditions; thrives near water sources

Toxicity

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Toxic; rhizomes and leaves contain irisin and iriflone glycosides; causes dermatitis, burning, nausea, and diarrhea if ingested; keep away from pets and children

Common Diseases

coronavirusLeaf Spotchevron_right coronavirusRoot Rotchevron_right coronavirusRustchevron_right

Common Pests

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Seasonal Care

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Resume regular watering and feeding as growth picks up.

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Peak growing season. Water and feed regularly.

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Reduce watering as growth slows. Stop heavy feeding.

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Minimal watering and feeding. Protect from frost if needed.