Yellow Oleander (Cascabela thevetia)

Yellow Oleander

Cascabela thevetia

Vibrant yellow blooms hide lethal toxicity, a striking but dangerous ornamental. Evergreen shrub or small tree; common names: yellow oleander, be-still tree.

Full sun
1–2/week
Moderate
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Plant Needs

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Sunlight Full sun to partial shade; requires at least 6 hours of direct sunlight for abundant flowering; avoid deep shade
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Watering Allow the top 2–3 cm of soil to dry between waterings; drought-tolerant once established; avoid waterlogged conditions
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Temperature Prefers warm tropical or subtropical climates; sensitive to frost, with severe damage occurring below 10°C
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Characteristics

  • Leaf: Linear-lanceolate, glossy green, arranged in whorls of 3–4
  • Flower: Trumpet-shaped, bright yellow, 5–7 cm long, fragrant in evening
  • Stem: Smooth, grayish-brown bark; milky toxic sap present in all plant parts
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Care Guide

Watering

Keep soil evenly moist but not waterlogged; increase frequency during prolonged heatwaves

Fertilization

Apply diluted balanced liquid fertilizer every 2 weeks. Discontinue fertilization in autumn and winter to support dormancy

Composted banana peel tea:Compost banana peels for 2–3 weeks to break down nutrients; steep in water for 24 hours, dilute 1:20 for root drenching; avoid using raw peels to prevent pest infestations
Pruning
  • Remove spent blooms regularly to encourage continuous flowering throughout the growing season
  • Thin crowded inner branches to improve airflow and reduce fungal disease risk
  • Prune to maintain desired shape in late winter before new spring growth emerges
  • Remove any dead, damaged, or diseased stems promptly to prevent spread of pathogens
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Toxicity

Warning: this plant may be toxic.

Pets & Humans

Pets: ASPCA: Highly toxic; ingestion leads to life-threatening cardiac and neurological symptoms

Humans: Contains cardiac glycosides; ingestion can cause fatal cardiac arrhythmias, even in small amounts

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Garden Uses & Culture

Culture: N/A

Usage: Ornamental landscaping; toxic sap historically used in traditional medicine (not recommended for home use)