Improving Peat Free Media

Vermiculite, perlite, horticultural grit and sharp sand
are all used variously to improve the water retention, drainage and aeration of growing media.

Which to choose?

Vermiculite

• naturally occurring mineral
• lightweight, absorbent brown/gold flakes
• can absorb 3 – 4 times its weight in water
• attracts plant nutrients eg potassium, calcium and magnesium
• aerates while retaining water and nutrients

Perlite

• made from volcanic glass
• lightweight, porous white granules
• improves drainage
• aerates

Horticultural/potting grit

• washed and lime-free.
• improves drainage
• attractive cover for exposed compost, reducing water loss by evaporation.

Recommendations;

Sowing seeds, pricking out seedlings.
Add vermiculite to peat-free compost in approximately a ratio of 1:4 by volume. A layer of vermiculite on top of seeds reduces water loss by evaporation.
Striking cuttings.
Add perlite or grit to peat-free composts in a ratio of 1:8 by volume.
Alpines, succulents or bulbs.
Add approximately one handful (50g) of potting/horticultural grit or perlite to one litre of peat free compost. A topping of grit 1 – 2 cm deep aids drainage and helps keep foliage dry
House plants
Be guided by what sort of plant it is. If it needs moisture retentive compost add vermiculite, or if it needs free draining compost add perlite or grit.
Hanging baskets
Add perlite to make the compost lighter. Add water retaining gel such as Swellgel will improve water retention (follow instructions on the packet).