Materials to use in Grow-Boxes and Seedling Trays

Here's the basic information you need to acquire and mix your organic soil mix for use in Grow-Boxes or seedling trays.

1) Soil mix percentages are figured by volume, and sand should be between 25% and 35%. The other ingredients, both type and amount, are your choice from the list below, based on cost and availability.

2) Extremely fine sand isn't the best, but you don't want anything too coarse either. It should be clean (no seeds, bugs, diseases, or dirt). In the USA we request "concrete sand".

3) The best soil mix alternatives are generally whichever are the least expensive among the following. Sawdust lasts longer than peat-moss, and perlite lasts longer than vermiculite, but sawdust takes some nitrogen while it is fresh (rarely enough to be a problem, if you are feeding properly), and vermiculite is
preferred by some growers over perlite because of the smaller particles.

4) Other materials to consider, in the order of our preference, include pine needles, coconut husks, rice hulls, coffee hulls, Bagass (sugar cane refuse), and the last choice would be leaves (but avoid scrub oak below 5,000 feet elevation and black walnuts).

These may be available free or at very low cost in many places. You should find a hammer mill or good chipper/shredder to chop the materials finely, and any of the above will work for you.