At the Botanic Gardens we stopped adding moss peat to our potting mixtures more than 15 years ago. Instead, we generally use ‘coco peat’ (or ‘coir’), made from the husk of a coconut and readily available as a by-product of the coconut industry, as well as composted pine bark.
A study just out from Italy gives the thumbs up to coco peat, although they still mixed in a little of the moss peat.
Classical peat is good addition to a potting mix - retaining water and adding extra nutrients – but its extraction from the wild is generally unsustainable. Note that I understand harvesting of living peat moss can be sustainable under certain circumstances. The dry moss peat is formed when the moss sphagnum and other bits and pieces partly decay in swampy land called peat bogs.
To extract the peat these wetlands are drained and destroyed. In addition to the environmental impacts, peat is now becoming difficult to source and expensive.
So the researchers from the University of Turin tested five different peat substitutes, mixed with some standard peat, and found that coconut fibre was the best.
They used camellias as their test plant because they grow well in acidic soils and are often grown in pots. (If you are interested, the cultivars were ‘Charles Cobb’s’, ‘Nuccio’s Pearl’ and ‘Dr Burnside’.)
They tested green compost (grass clippings and leaves), pumice, fibre from coconut husks – composted and uncomposted, and pine bark.
Each of the alternatives was as good as, or better, than straight moss peat, except for the green compost which raised the pH of the mix. Coco Peat was recommended, with some adjustment to fertilizing and watering compared to straight peat.
If you use coco peat straight, you would definitely need to add a little something for you plants to live on.
Image: Coco peat, from a supplier site