Scoria is a natural, locally sourced volcanic rock used to improve drainage, aeration, and structural integrity in growing media. Recognisable by its deep red to dark brown colouring—caused by naturally occurring iron-rich minerals—scoria is a dense, porous aggregate that stays firmly in place within your mix, providing long-lasting aeration and helping resist compaction over time.
Available in two grades—fine (1–6 mm average) and coarse (8–10 mm average)—to suit different applications. Fine grade is ideal for potting mixes and containers where consistent aeration is needed without creating large air spaces. Coarse grade delivers greater drainage and airflow for large containers, raised beds, bottom-of-pot drainage layers, or heavier mixes that benefit from improved structure. Both grades can also be blended to achieve a custom particle size distribution.
As a natural volcanic rock, scoria contains silica, iron-bearing minerals, and naturally occurring trace elements that weather only very slowly over time. It also has a modest cation exchange capacity (CEC), allowing it to retain small amounts of positively charged nutrients and help reduce nutrient leaching. Extremely durable and resistant to breakdown, scoria maintains its structure for many years and can be reused across multiple growing cycles. Being locally sourced also helps reduce transport distances compared with many imported volcanic aggregates.
