On Sat, 25 Apr 2009 07:49:32 +0100, Chris Hogg wrote:


Ericaceous plants grown on alkaline soil suffer from iron deficiency
which results in yellowing leaves, aka chlorosis. Manganese deficiency
can also be a problem. This is because iron and manganese are not
soluble in high-pH (alkaline) soils, so are not available to the
plants. I've not tried watering chlorotic plants with ferrous
sulphate. It would provide soluble iron for a limited period of time,
I guess, but it's almost impossible to acidify alkaline soil
permanently, so the effect wouldn't be permanent. Nor would it do
anything for manganese deficiency, although in general this is less of
a problem. Ferrous sulphate is in itself fairly acidic, so it would
help lower the pH of weakly alkaline soil for a period of time.

Better than ferrous sulphate is sequestered iron and manganese,
available in sachets from garden centres under the name Sequestrine.
This is iron and manganese in a form that is soluble in alkaline
soils, so remains available to the plants for longer, until it's all
used up or washed out. But if you've got ferrous sulphate for free,
I'd go ahead and try it. Just make sure you've got the dilution right
or you may damage the plants.

As to raising small heathers in areas of unsuitable soil, you could
make pockets of acid soil for them to grow in, but eventually these
would become alkaline over a year or so, or you could grow them in
pots of acid soil sunk into the beds, when they might stay acid for a
bit longer. Either way, you can always water with Sequestrine if they
show signs of chlorosis.

Thanks so much for that reply - I was wondering about the iron-pH link
and hadn't realised manganese was an issue too.

I'll do as you say, get the Sequestrine while trying the ferrous
sulphate too on a couple of areas.

Yes, good idea on the buried pots while the little heathers grow a
bit.

Much obliged.