Plant Doctor Archive

Can I use sphagnum in my potting mix?

Question A FRIEND of mine told me she uses chopped-up sphagnum moss mixed in with her potting mix for hanging baskets and containers because she believes water crystals, when they swell, can damage the plant’s roots. Is this true?

Answer THE best sphagnum to use is the pressed basket liners. As you line the basket, water the liner, which swells, and then plant up as per normal. Loose sphagnum is really hard to get evenly distributed around the basket and the birds have a field day picking at it, as they do coconut fibre, for their nests.

As far as mixing sphagnum with potting mix, you would need to keep the mix well watered and not let it dry out, as once sphagnum dries it repels water like peat does and is hard to wet again — this will do more damage than water crystals shrinking and expanding. Wetting agents and water storage crystals added to potting mix (Yates Hanging Basket Mix contains both) are the best way to go. Water crystals do not cause damage to plant roots.