Joe Davison, an auricula grower in England, uses the following potting mixes.
8 pints John Innes No. 2
2 pints Rotted Beach Leaves
2 pints Perlite
1 pint Horticultural Sand
2 1/2″ pot of crushed Oyster Shell
2 1/2″ pot of crushed Charcoal
1 heaped desert-spoon Seaweed meal
1 heaped desert-spoon Nutrimate (organic growth
Same as above, but instead of Beach Leaves, I add
2 pints of Peat based Multi-purpose Compost,
and do not add Oyster shell.
I do not grow many Alpine Auriculas, so I use the same mix as I use for selfs, with good results.
Much hype and mystique is given to growing mixes. My advice is, if you find one that works for you, stick to it. The tricky bit is in the feeding of Auriculas, but that is another story!!!
I understand that store-bought John Innes is not available in North America, so for anyone who wants to try making some, here is the recipe.
John Innes No. 2
7 parts Loam (soil)
3 parts Peat
2 parts Horticultural Sand
to 8 gallon of the above mix, add:-
1 1/2 oz. of ground limestone
3 1/5 oz. of Superphosphate of lime
3 1/5 oz. of Hoof and Horn
1 3/5 oz. Sulphate of Potash
Virgin soil is to be prefered, from a meadow. Mole-hill soil is best. Garden soil makes a poor second.
The advantages of Nutrimate are debatable. It has a high content of Humate ( look up Humate, on the net)but I know there are products in America, containing Humate.
Good growing, and good health