What should I do if bark mulch smells bad

A fresh heap of bark should carry the clean, resinous scent of woodland after rain. When instead it reeks of vinegar, sulphur or ammonia, the pile has turned anaerobic. Compaction and excess moisture starve microbes of oxygen, and fermentation sets in, brewing acids that can scorch roots and wrinkle noses.

First, resist the urge to tip the sour heap straight onto beds. Fork the bark onto a tarp or standing and fluff it up in shallow layers; the harsh odour usually softens as oxygen floods back. Turning the material each day for a week speeds recovery. If the smell lingers, sprinkle garden lime lightly while mixing: this neutralises acids and steadies pH.

Once the aroma resembles forest floor again, spread no more than five centimetres deep and keep the layer clear of plant crowns. Any residue of acidity will leach harmlessly with the next shower.

To avoid a repeat, store deliveries from AHS LTD on railway sleepers or pallets so rain can drain and air can circulate. Cover loosely with a breathable sheet rather than a tight tarpaulin, and aim to use the bark within six weeks of arrival. A living mulch should smell alive, not like a brewery gone wrong.