Whether it's used for outdoor containers or indoor houseplants, a soil mix that both drains well yet retains moisture is the basic goal of good potting soil.
The five varied recipes below are each lighter or heavier than the other. The indoor gardener should experiment with a couple to determine which type is preferred. These soil mixes recipes work well for outdoor as well as indoor plants.
Basic Potting Soil Mixes
There are many different recipes for making your own potting soil. The majority of indoor plants prefer their soils slightly into the acidic range on the pH scale. The potting mixes below will create general soils that reflect this preference, falling at about 6.5 - 7.0.
Soil mix #1: 1/3 topsoil
- 1/3 compost
- 1/3 builder's sand
- Soil mix #2: 1/4 compost
- 1/4 builder's sand
- 1/2 peat, coir, or rice hulls
Soil mix #3: 1/4 compost
- 1/4 topsoil
- 1/4 vermiculite
- 1/4 peat, coir, or rice hulls
Soil mix #4: 1/3 compost
- 1/3 garden soil
- 1/3 builder's sand
- Soil mix #5: 4 parts commercial potting soil
- 1 part compost
Special Houseplant Soil Additives
Worm castings are a valuable addition to any potting soil or soil-less potting mix is a tremendous advantage for houseplants. Vermicompost may be the single best extra additive because of it's high nutritional value. Leaf mold is another excellent soil stabilizer to consider adding to potting soils.
Why Not Peat Moss?
Peat has been one of the favorite soil additive for many years. Peat Moss capable of absorbing 10-20 times its weight in water. Along with beneficial bacteria it contains a natural fungicide that is a barrier to several troubling fungi including damping off, which is the bane of a seed-starter's existence. For this reason, using peat in special seeds-starting soil is optimal.
One of the favorite places for gardeners to use it in is potting soil. It's a natural product that's harvested from ancient cold-climate peat bogs in Canada, Europe and parts of the United States. Unfortunately, these bogs are being destroyed with all the harvesting or mining of the peat. This causes permanent and destructive changes in the eco-system including the loss of habitat for creatures whose lives depend on these peat bogs.
The use of peat (at least to excess) is no longer considered an environmentally sound practice. It's treated as a non-renewable resource because although it is technically renewable, peat moss takes about 1,000 years for a bog to grow 1 yard of peat. This makes it un-renewable in a lifetime or even a grandchild's lifetime.
The Peat Moss Alternatives
There are a couple of effective alternatives to using peat in our potting mixes.
Coir - (pronounced koy-er) is the hairy outside layer of husk that surrounds the coconut shell. You may have heard of it referred to as "coco-peat" or "coir-peat". What makes this product environmentally friendly is that it's simply a by-product of the coconuts that are grown for their meat. Husks that would be other wise disposed of as waste.
Coir comes in blocks that expend like crazy when soaked. Coir can be used as a planting medium, but it needs to be blended with a nutritional component such as compost. There's not much nutritional value in coir by itself. A slow-release fertilizer may also be added into the soil mix. Coir retains moisture extremely well and is more eco-friendly than it's peat counterpart It's shipped dehydrated making it lightweight.
Rice Hulls - Rice hulls are a good alternative to peat as they lighten the soil, absorb water well, and offer good drainage. Before rice grains are converted (parboiled) or polished, they are dried and the hulled. Hulls that would otherwise be tossed out, can be used as a soil-less medium just like coir or peat. They're very thin, and nearly weightless.
They can be added in potting mixes, but even on their own they have merit as a soil amendment by both aerating, and retaining water. Rice hulls are a nice alternative to peat as it's much cheaper (not to mention easier) to gather rice hulls as opposed to harvesting peat moss.
Commercially bagged potting soils are expensive, so mixing plant mediums at home saves money for the indoor gardener.
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