According to Paul Stamets' excellent and beautifully illustrated
Psilocybin Mushrooms of the World (IMHO Paul is the Shulgin of Psilocybes) the strongest species are, in order:
Azurescens 2.5
Baeocystis 1.6
Bohemica 1.5
Semilanceata 1.4
Cubensis 1.3
Cyanescens 1.3
This is not as simple as it seems though: There are 3 main psychoactives: (1)psilocybin, (2)psilocin (1 with OH instead of phosphoryloxy) and (3) baeocystin.
The effects of each is different and the different trips thereby had are often attributed to this, as well as the fact that the actual concentration in a single strain will vary considerably depedning on substrate, conditions etc.
so the above scale is only a guide. In particular note that these figures are from dried specimens, and unless care is excesised in the drying process a lot of goodies can be lost. Personally I bioassay a carpophore before making assesments about the potency of a particular flush, because I have encountered so much variation that one is really making educated guesses until one tastes..... I'll say this much though: I have handled shrooms so strong that I could actually feel the effects from the tiny amount absorbed through my skin, and while that's generally restricted to Azuresens, I have found cyanescens strong enough to do this as well. Conversely, one patch were less than half as strong as what was normally expected. This is typical of wild strains, and applies less to cultivars.
It also varies greatly between these species as to the proportions of each alkaloid.
Azurescens, by far my favourite (very clean, powerful) has over 80% of it's actives as psilocybin, and the remainder equal portions of psilocin and baeocystin.
Semilanceata has about the same proportion of psilcybbin, almost no psilocin, but a significant amount of baeocystin present.
Cubensis has almost equal proportions of psilocybin and psilocin and almost no baeocystin at all.
Cyanescens has about 65% psilocybin, 30% psilocin and 5% baeocystin.
Older mushrooms can give much less agreeable onsets than fresh, new ones, and leave you more exhausted and feeling trashed.
For home cultivation there are other factors to consider, and one important one is the aggressiveness of the mycelium of the cultivated strain. Cyanescens is probably the most forgiving in terms of tolerance of conditions; once it gets going this stuff is fast if he strain isn't too old- strains lose their growth aggression after a while, though this is less prevalent with mixed strains, as apposed to pure cultures.
Primordia formation- the precursor to pinheads- is stimulated by slightly different means in differnt shrooms. In general the CO
2 concentration needs to be kept lower along with that of other metabolite gases, so the airflow is increased, the humidity kept around 95% especially throughout the pinning, and possibly a temperature drop is needed as well.
Mycelium growth is generally done in darkness; some species of mushroom require light to stimulate primordia development, so a 12 hour lighted cycle may also be necessary.
If you're serious about this try and get hold of Paul Stamets and J.S. Chilton's Musgroom Cultivator (which has been mentioned before)- it is one of the best books on growing mushrooms, and specifically includes several Psilocybe species.
I guess yu already know this but the greatest enemy of mushroom cultivation is contamination: you need to get good with sterile technique and don't gamble with contaminated cultures- it could be anything, including some very nasty bacteria.
Psilocybin is so similar to serotonin (once described as the reality filter neurotransmitter, although that's probably more a mainstream bastardisation than anything) that there have been times when I have wondered if the brain works better on a very small dose.
Probably that's just me being crazy.
There's a story I was going to omit but I can't help myself now. Tee hee.
There was this one time when I was posessed by the peculiar notion that I should test this theory I had on the efficacy of psilocybin as a neurotransmitter- I was feeling pretty lethargic after a fairly long day but had to do an all-nighter, and I knew I had to be finished before 7am the next morning, and I was honestly ready for bed. So I stopped by a favourite spot on the way in to this particular locus of employ and under the half-moon and partly cloudy sky, ingested 4 lovely, juicy cyanescens. And went on to build a LAN in record time whilst tripping off my dial. What the fuck was I thinking? I'm not sure.... "This will be a great story I can tell my kids" perhaps?
Don't do this at home. I didn't