Al's gritty mix is a coarse and long-lasting potting mix that provides superior drainage and aeration, properties that are less than ideal in most commercially prepared soils. It is a carefully designed mix by Al (aka tapla) from Gardenweb.com website. Many members of Garden Web are using it and cannot praise it highly enough. Combining two inorganic materials and fine conifer bark, produces a soil mix that is extremely durable and resists breaking down between repots. The Gritty Mix is recommended for any plant material that will be in the same soil longer than a single growth cycle (one season). The ingredients for the gritty mix are 1 part Turface, 1 part Granite Grit, and 1 part Fine bark.
The ingredients are:
Turface (calcined high-fired clay). It is very porous and used in the soil to hold water and nutrients. Look for size "Turface MVP" or "Turface AllSport" at John Deere Landscapes dealers. The products are identical.
Granite grit. It holds no water or nutrient, except as a film on its surface. It is used to provide better drainage and reduce water retention. For brand “Gran-I-Grit” use 'grower size'. If you can find New Ulm cherrystone, use #2 size. For other brands, the ideal size is 1/8”.
Fine bark. It is used to hold water and nutrients. Use uncomposed “Fir” or “Pine” bark. Ideal size is 1/16” to 1/4”.
You should also add in gypsum as a CaSO4 source. Add 1 tbsp to every gallon. Because gypsum contains no Mg, use Epsom salt for MgSO4. Use 1/8 -1/4 tsp Epsom salts per gallon of fertilizer solution each time you fertilize.
Adjusting the mix
This mix can be adjustable to your needs. For better water retention add more turface, less granite grit, while keeping the amount of fine bark at 1/3 volume of the mix. EG. 4 part turface, 2 part granite grit, 2 part fine bark. For better drainage, aeration, and less water retention, you can use 4 part granite grit, 2 part turface, 2 part fine bark. I don’t recommend using too much granite grit, however, as you will have to water very often. The original 1:1:1 ratio already has much more aeration and drainage than any other potting mix out there.
Preparing the materials
It is recommended that all three ingredients be screened with a window insect screen (usually 1/16"). Fine bark should be screened with a 1/4 hardware cloth to get rid of the larger particles on top before screening the rest with the insect screen. It is also recommended that fine bark be left out to dry for easier shifting.
Windows screen over a 20 gallon rope tote 1/4" hardware cloth on top of the windows screen
Final product (1:1:1 ratio)
Finding The Materials
Turface: use this website - http://www.turface.com/distributors/state/
Granite Grit: Use google maps or MSN Yellow Pages. Use keywords such as : feed store, poultry feed, stone amendment
Fine Bark: Uncomposed Fine bark can be labeled as “soil conditioner”, “mini bark nuggets”, “bark mulch”, “Orchid Bark”.