Gardening glossary
Ericaceous (acid-loving)
Ericaceous is the gardener's shorthand for acid-loving plants and the compost they need. The name comes from Ericaceae, the heath family, which includes heathers, rhododendrons, azaleas, blueberries, cranberries, and pieris. Camellias, gardenias, magnolias, Japanese maples, and conifers are not technically in the family but share the same low-pH preference and are treated the same way.
Acid-loving plants need soil pH between 4.5 and 5.5 (some, like blueberries, are happiest down at 4.5–4.8). At higher pH, iron and manganese lock up in the soil and the plants develop lime-induced chlorosis: young leaves yellow between the veins while the veins themselves stay green. Left unfixed, the plant slows, drops leaves, and eventually dies.
Where this matters:
- **Hard-water tap water** typically runs at pH 7.5–8.5 and will gradually push pot pH up. Use collected rainwater for ericaceous container plants whenever possible. - **Most garden soils** in chalk or limestone regions are too alkaline for ericaceous plants in the ground — these plants must go in pots or raised beds filled with ericaceous compost. - **Standard multipurpose compost** is buffered to around pH 6.0–6.5, which is fine for most plants but slightly too high for ericaceous species in the long term.
Ericaceous compost is peat-based or peat-free compost amended to a pH of around 4.5–5.5 with sulphur, composted bracken, or pine bark. Use it neat in pots for camellias, rhododendrons, and blueberries, or mix half-and-half with garden soil for planting holes.
To keep pH down over time, mulch with pine needles or composted bark, water with rainwater, and feed with a dedicated ericaceous liquid feed (typically slightly acidic with chelated iron). A simple pH probe checked twice a year confirms the soil is staying in range.