Coir is ground up coconut shells and fibre, great for the producers in the developing world as they can get money for what would otherwise be a worthless waste product. I go through about eight coir bricks a year. But it contains scarcely any nutrients for plants. Some suppliers, eg the Organic Gardening Catalogue, sell sachets of nutrient powder to add. I also add a double handful of seaweed meal to each brick, to help with water retention. I don't know if it's suitable for bonsai, I'll leave that for someone else to answer. It's great for seeds because there are no weed seeds in it, so you know that whatever comes up is what you've sown. I don't find it so useful for growing bigger plants in pots because it's so light they fall over.
And I don't think it was a silly question.
Last edited: 09 August 2017 23:37:38