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St John's Wort

Hypericum perforatum

herb

verifiedReviewed by the GreenScout Team

St John's Wort is a hardy perennial herb with small, narrow leaves and bright yellow, five-petaled flowers that bloom profusely in summer. It is an extremely vigorous, drought-tolerant plant that has been used for centuries in traditional herbal medicine. The plant contains compounds that are photosensitizing and can interact with medications.

Common Problems

Select the problem your St John's Wort is experiencing to get a treatment guide.

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Overwateringchevron_right

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Root Rotchevron_right

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Yellow Leaveschevron_right

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Slow Growthchevron_right

Care Guide

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Light

Full sun (6–8 hours daily); requires bright light for optimal flowering and compound development.

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Water

Low water needs; water moderately when young; once established, very drought-tolerant. Minimal watering needed.

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Soil

Well-draining soil; tolerates poor, sandy, rocky, or clay soils; neutral to slightly alkaline pH (6.0–7.5) preferred.

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Fertiliser

Minimal fertilizer; generally thrives without supplemental feeding; avoid overfertilizing.

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Temperature

Very cold-hardy; tolerates a wide temperature range (40–85°F); thrives in cool to warm climates.

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Humidity

Low humidity preferred; does not require misting; tolerates dry air well.

Toxicity

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Non-toxic but photosensitizing; excessive skin contact followed by sun exposure can cause dermatitis. Interacts with many medications; consult healthcare provider before ingestion.

Common Diseases

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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.

Frequently Asked Questions

Is St John's Wort safe to take with other medications?

Use caution — the plant contains compounds that interact with many medications, so consult a healthcare provider before ingestion; it's also photosensitizing, meaning excessive skin contact followed by sun exposure can cause dermatitis.

How much care does St John's Wort actually need?

Very little — it's an extremely vigorous, drought-tolerant perennial once established, needing only minimal watering and no supplemental feeding to thrive.