Indoor Gardening and Houseplants: A Discussion about Houseplant Soils (long post), 1 by tapla

tapla wrote:
My intent in starting this thread was to let you know you needn't depend on a bagged soil for your plants. You can do much better by mixing your own soils, and in the long run, if you purchase larger bags of ingredients, the cost for a premium soil will be less than what you pay for the bagged media most of you are using.

I grow virtually all my houseplants, including cacti and succulents in a very coarse mix of equal portions by volume, of a baked clay granule called Turface, crushed granite (chicken or turkey grit), and either pine or fir bark. The mix will retain its structure, guaranteeing excellent aeration, and stability long after peat and even bark based soils have collapsed.

I so often say that it's not too important what soils are made from, as long as they retain the right proportions of air and water for the life of the planting. The soil you see below will do that. Because it drains freely, you need to water and fertilize more frequently, so you need to decide if you're willing to trade convenience for considerable improvement in vitality.

This particular soil is my basic mix for houseplants. I've grown in it for more than 10 years, and I can attest to the fact that it is far superior to any bagged soil I've ever used. I'm not trying to sell you on "my mix" or any particular mix of ingredients. I'm trying to sell you on aeration and stability - two things you do not get from a bagged soil.

1 part pine or fir bark (appropriate size)
1 part Turface (baked clay granules)
1 part crushed granite (chicken or turkey grit)
gypsum
controlled release fertilizer (if the season is appropriate)

I hope there are lots of questions or comments.

Al