Chris Hogg wrote:

It's 95 % w/w ferrous sulphate heptahydrate and 1 % w/w suphuric acid.

You can use it on ericaceous plants (rhododendrons, azaleas, camellias
and heathers) if they are growing in alkaline soil and showing signs
of chlorosis (yellowing of the leaves). They grow best in acid soil.
Ferrous sulphate will go a little way to acidifying an alkaline soil,
at least for a few months, and also provide the iron that the plants
are lacking. Personally, I think Sequestrine is more effective.

Chris, thanks a lot. That's great news, as we have 15 rhodies growing
in soil that is only partly acidic and they need the extra help each
year.

You did notice the 1 % sulphuric acid, didn't you? Is it that that
amount is so slight it's no danger to plants?

And thanks for the warning re. black fingers! I used a little this
morning on a patch of moss that has developed within an aubretia plant
and I wondered about the slight stain on one of my fingers afterwards!

Eddy.