House plant soil formula

(Question)

I wish to make up my own soil for indoor and tropical plants.
I have available a compost pile, peat moss, pearlite and sand.
Is it easy to make your own? What do I need and how much of each?
Thanks

(Answer)

There are many different potting soil recipes available. There are a few things to keep in mind however. Soil will provide the nutrients, sand and perlite will provide drainage and compost and vermiculite will help retain moisture. You should not use garden soil without sterilizing it as it contains insects, pathogens and weeds that will affect your indoor plants. You can sterilize a small amount of soil by baking well moistened soil in a 180°F oven for 45 minutes.  A meat thermometer will be helpful to make sure the soil reaches a temperature of 175°F but don’t overheat it so that helpful soil microorganisms will be retained. Be aware however that this is a very stinky process! Make sure that you are using sharp builder’s sand in the recipe as beach sand is too fine to provide proper drainage.  Lastly the compost that you use should be made in a hot compost pile or alternatively as vermicomposting so that you don’t introduce any weeds into your potting soil from this.

Below are a few examples of soil recipes that are available from The New Seed-Starters Handbook by Nancy Bubel and from the University of Florida Extension Services.

Simple Potting Soil

  • 1 part compost; 1 part vermiculite

OR

  • 1 part compost; 1 part garden soil; 1 part sharp sand, vermiculite or perlite or a combination of the three

Lean Potting Soil (useful for plants that grow slowly)

  • 1 part soil; 1 part perlite; 1 part vermiculite; 1 part sphagnum moss; 1 part sharp sand

Foliage Plants

  • 2 parts peat; 1 part perlite; 1 part coarse sand

Succulents

  • 2 parts soil; 1 part peat moss; 1 part perlite; 1 part coarse sand

Bromeliads

  • 1 part peat; 1 part bark; 1 part coarse sand

Seedlings

  • 2 parts compost; 2 parts peat moss; 1 part vermiculite (pre-wet)