Hi

I use John inns no 3 or 2 loam/soil based compost and add xtra grit for good drainage (mix it in) , dont use multi-purpose compost as it hold too much water over winter which is not good for the roots of acers and quickly runs out of food after a short period of time , I know its cheaper to buy but in the long run its a waste of money.

Most acers dont like lime but if growing in a pot it quickly washes out with regular watering and I have never had a problem using John innes.

Gg