Mark wrote: wrote:

I know how to increase the soils PH. But what do i add to bring it
down.

Hi Mark,

There are several right ways and one wrong way.

Do not use Aluminum Sulfate. The aluminum builds up in the soil and is
toxic to many plants including rhododendrons and azaleas. There is one
exception. Aluminum Sulfate will normally make blue/pink hydrangeas
bloom blue since they require both aluminum and acidity to bloom blue.

The right ways include:

Ferric Sulfate
Flowers of Sulfur (powdered sulfur)

If the soil is too alkaline, acidity may be increased by adding flowers
of sulfur (powdered sulfur) or iron sulfate. I add 1 tablespoon of
sulfur powder around the base of any plant showing signs of chlorosis.
Around established rhododendrons and azaleas, do not disturb the shallow
roots. Sprinkle the sulfur under the mulch and then replace the mulch.
Do not use aluminum sulfate. Aluminum can build up in the soil to toxic
levels eventually. One very common source of chlorosis is when lime
leaches out of concrete, such as from a foundation or walkway, making
the nearby soil more alkaline. This problem decreases each year as the
concrete ages. An annual application of sulfur can compensate for this
problem.

For table on how much elemental sulfur is needed to lower soil pH, visit:

http://rhodyman.net/rarhodyho.html

and click on "Soil pH"

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Cheers, Steve Henning in Reading, PA USA - http://rhodyman.net