Q: About designing planting mixes.


Special mixes A: When creating a planting mix, think about what you want to achieve. Do you want an acidic mix or a neutral one? Do you want plenty of aeration or a dense, waterlogged mix? Do you want a coarse or a fine mix? Review the attributes of each of these in the previous FAQ pages, then select your ingredients to provide the desired effects. This is where the art is, and where things get interesting!

Charcoal may have some chemically active properties, but I do not really believe it. In terms of its physical structure, it is an aggregate.
Gravel is similar to perlite, but is much denser.
Peat provides water retention, but not much aeration. It is very acidic, but eventually breaks down.
Perlite provides excellent drainage and an airy mix. Large chunk perlite it is too coarse for tiny plants, so select the grain size wisely.
Pumice is similar to perlite, but heavier.
Sand (Silica-based) provides good drainage, but smooth-grained kinds can lock out air.
Sand (Calcium carbonate-based) creates a well-drained, alkaline medium.
Sphagnum (live) provides water retention and is very acidic, but most species are coarsely grained and not suitable for tiny plants. It is excellent for rooting plants, and tempermental Nepenthes and Darlingtonia, but can be tempermental itself!
Sphagnum (long-fiber) provides water retention and is very acidic, but is coarsely grained and not suitable for tiny plants. It is also expensive (financially and environmentally).
Sphagnum (milled) is like long-fiber Sphagnum, but is fine grained.
Vermiculite is similar to peat but is not acidic. It breaks down.

Combine your ingredients to achieve the goals you desire. A tuberous Drosera will want a sandy mix (perhaps 2 or 3 sand: 1 peat). Sarracenia like pure Sphagnum or sand & peat. Mexican Pinguicula like a number of compounds---my usual mix for them is 3 perlite: 2 vermiculite, but I'm not very happy with it.

Some carnivorous plants (or at least their growers!) prefer quite complicated planting mixes that involving any number of the elements profiled in this FAQ in combination with compost, Osmunda fiber, pine needles, oak leaves, or other additives. Feel free to experiment and by all means report your findings. Sadly, there are no solid, reliable recipes that seem to work for everyone. I mention some of these mixes in the section of the FAQ where I discuss each genus.

Page citations: Rice, B.A. 2006a; personal observation.