One article that was on our old website, concerned soil mixes. Unfortunately I was not able to save that post, so thought I would take the time to re-write and update it here, especially as it is the time of year when most of the germination is done.
Seed Sowing
For seed sowing we make our own mix based upon a peat base (from sustainable sources) with the addition of various components according to what we are doing with it.
Initially riddled at 7mm, in order to remove the larger pieces from the mix (these are not wasted, we use it to mulch round our garden plants). To this sieved mix we add 1 part sharp sand, 1 part vermiculte and 1 part perlite for every 7 parts of the peat base. This gives a 7:1:1:1 mix, which is open (for good root development of the seedlings) but also moisture retentive (to help with the intial germination). Unless we are dealing with finicky seeds, we no longer sterilise. Where we do sterilise, we do so after the seiving stage and only to the peat base as the other componenets are naturally sterile.
Growing On.
Same mix ratios, but we do not seive this mix, preferring to just pick out the larger unwanted twigs and branches so common in commercial peat based mixes (likely due to bulking out with coarse shredded material
Specialist Mixes
Cactus and Succulents get extra drainage material so the rations go down to 4 parts peat base to give a 4:1:1:1. For seed sowing here the riddle gets set at a much finer 4 mm.
Sterilising
To sterilise the mix, we use the oven tray method - basically put the mix in an oven proof tray (it must be damp for this to work quickly) and then place in an oven at least 150 Deg C (300 F) for an hour. The steam produced and the heating of the centre will serve to kill all weed seeds and pathogens in the mix. Allow it to cool covered, so no new pathogens are introduced, then re-wet it (so that it is damp) just prior to use. Small seeds, where the resultant seedlings could be swamped by weeds or other unwanted growth, will especially benefit from this. Dont be fooled into thinking that shop bought mixes will be free from problems, they never are. You have no idea where they were mixed or how long they were standing in the yard or shop - all would be a source of problems and the only way to be sure is to sterilise. Smaller amounts can be microwaved on 75 - 100 % power for around 15 minutes or so per 2 litres of mix.
