I sometimes recycle potting soil, but only after screening out the dust and fines through a 1/16" mesh. This gets rid of fine sand and the broken-down organics which pack and exclude air.
I'm always interested in hearing about a premium potting soil, because most bagged mixes are now made from shredded scrap wood and tree trimmings from landfill operations. As such, they're good for one season, and tend to be marginal at that. Check the labels; "Composted Forest Products" and "Aged Forest Products" are code for ground-up scrap wood.
Wood fibers (cellulose) break down quickly and support invasive fungal overgrowth (mushrooms, dry-rot). It's one of the worst things to grow in.
Ground bark is one of the best and most stable potting ingredients available. The function of bark in nature is to resist breakdown, and protect the relatively fragile wood fiber of the tree.
Peat of one sort or another is a classic, time-honored and common potting mix ingredient, and while superior to wood, it's fine-textured, and can pack down. When it's wet, it holds too much water with little air space, and when it's dry, it's difficult to re-wet.
My favorite potting mix is home blended, with ground bark as the primary component. I use fine orchid bark or landscape bark as the primary component. (Landscape bark is cheaper, but involves a little more work to screen out the dust, oversized chunks and other junk. Always use bark chunks, not shredded, fibrous, or 'hairy' bark)
Search the web for 5-1-1 container mix, there are a few YouTube videos on this subject as well. Briefly, it's:
5 parts 3/16"—1/2" bark
1 part 'medium' perlite (no dust)
1 part peat (or peat-based soil mix)
The bark will need lime. About a week before using the bark, moisten it well and add 1/2 to 1 tablespoon dolomitic lime per gallon of bark. Shake or stir, bag it up, and let it rest for a week or so.
Blend and moisten the ingredients just before use, and when potting up, add a time-release fertilizer. Thereafter, give regular feedings with Dyna-Gro Foliage Pro. It has an ideal nutrient balance (including micros) as well as calcium, important in soilless mixes. A dilution of 1/4 tsp/gallon is suitable for use at every watering.
This mix is stable, holds water well, and has plenty of air space to keep roots healthy. It will last for years. It's made a huge difference in the health of my container plants.
