Are Mulch and Compost Safe for Your Garden? The Oleander Warning

Mulch (surface layer) and compost (soil amendment) are garden staples—but not all plant material is safe. Oleander (Nerium oleander) is highly toxic: all parts contain oleandrin, a cardiac glycoside. A few leaves can kill a child; sap causes skin irritation; dust from dry leaves is hazardous if inhaled.

Safe Handling of Oleander

• Prune only after heavy rain (reduces dust).
• Wear gloves, long sleeves, eye protection.
• Never burn—smoke is toxic.

Can Oleander Be Composted?

Research (Reclamation Calgary) shows oleandrin degrades after ~50 days in active compost. Finished compost tested on lettuce and tomatoes showed no detectable toxin. However, using oleander as mulch is riskier—less decomposition occurs on the surface. If mulching, restrict to ornamental beds, never vegetable gardens.

Best Practice

Compost oleander separately, ensure full decomposition (>50 days, unrecognizable), and always wash produce thoroughly. When in doubt, exclude it.