I have been looking for a Magnesium additive for a few of my trees that I think have an issue. I have a maple in a garden pot and a Fuji cherry bonsai that last year had a yellowing of the leaves. A wise man once told me that feeding won’t necessarily help the tree. The tree needs magnesium to help it break down the fertiliser.
I searched the local garden centres for the old En-Mag product with no joy. I had actually given up when I went into a very local, pokey family plant and paint shop and found Chempak’s Magnesium product and, to make it even better, their Trace elements one as well! I’m not sure they make these any more, haven’t seen them for a long time, perhaps old stock, but they’ll do me.