...This year I知 looking at the wide varieties and just getting confused.
Do I need all of the different varieties?
There can be a lot of prices differences - does it make a difference?
Should I use seed compost and then pot out into no1 type etc.
So many questions!
Mark
Hi Mark,
As has already been mentioned, commercially produced compost is just used as a growing medium. Some use it to fill entire beds or mix it with the existing soil to use it as a soil conditioner, but its main use is for sowing seed and potting on.
Now, being an old fud who has been doing this for well over forty years, I remember the days when the choice was not so overwhelming. All the books and magazines talked about John Innis composts and the odd mention of the newfangled (to me at the time) multi-purpose compost.
My view of them was somewhat skewed by the fact that the multi-purpose compost of the day had no soil in it and was almost 100% peat with some "added nutrients". I could never find out exactly what those nutrients were (are?) as there was no mention of exactly what quantities have been added. It would also be very hard to re-wet if it dried out. It does not seem to be any different today. I suspect that batches vary, even from the same producers. What I do know is that it usually produces good fast growth for the first few weeks, and then it is up to the grower to top up the nutrients as the plant requires, usually by adding liquid feed. Nothing wrong with all that, but you do need to be aware of what nutrients the plants need and more importantly; how much to apply and at what interval. You can of course just keep repotting into new compost as your plants grow, but you are repotting into compost that contains the same level of nutrient as the seed was sown in. Nothing wrong with that, as long as it works for you.
John Innis is actually a formula, not a brand name. It is a staged growing programme that takes plants from seed to mature plant by increasing the amount of nutrient in each potting on mix. The base soil mix is also formulated to keep everything constant.
JI seed compost is just the base mix with added phosphate to promote root growth once the seed has germinated.
JI No.1 is the base mix plus one measure of the nutrient mix.
JI No.2 is the base mix plus two measures of the nutrient mix.
JI No.3 is the base mix plus three measures of the nutrient mix.
The formula is readily available on the internet, but the simplest explanation I can find is here:
https://www.rhs.org.uk/advice/profile?pid=952I hope this helps,
Ralph.