multipurpose with John Innes for cosmos?

[amoreoamicizia]

I bought some cosmos today at the garden centre and they said I should plant using multi-purpose with added John Innes. On the other hand, I've just read in another thread that they thrive in poor conditions which is the direct opposite of John Innes (added nutrients). I didn't buy the compost so which should I go for?

1. Very old compost from a bag that was left over from a couple of years ago (never opened so goodness knows how it is now!)
2. Bog-standard cheap multipurpose from a supermarket, most likely.
3. Multipurpose with added John Innes from the garden centre, more expensive.

Thanks🙏

IME they grow like weeds so plant in any old compost

Thanks, it would be good to save a few pounds at the moment 😊

multi-purpose with added John Innes is a rip-off.
It's either council recycled-garden waste or proper John Innes mixture, they are not the same.

I read quite recently that they grow ok in quite poor soil.

Yes, I googled a bit more after posting and it seems nutrients encourage foliage sometimes at the expense of flowering in cosmos. On the other hand, the soil/compost should be well-draining which is probably why they do well in the ground here where I live because we have sandy soil. So overall, neutral to poor sandy soil is wanted.

I planted a new raised bed full of cosmos after filling it with spent compost from various pots and they have grown super bushy and covered in buds. Will probably need to get rid of the spent compost over winter but has worked well for a temporary show.