(paghat) wrote:

"Correcting" soil with peat, sphagnum, or acidifying fertilizers does more
harm than good even in the short run.

Actually the correct way to raise a broad spectrum of acid loving
rhododendron and azalea plants in an alkaline area is to use a raised
bed. You build up a raised bed with landscape timbers (nontoxic treated
wood or wood substitute). Then you get acidic or neutral soil and mix
it with good organic material. Since rhododendrons and azaleas have
shallow roots, if the raised bed is at least 10 to 12 inches high with a
gravel layer on the bottom, the alkaline soil will have no effect on the
rhododendrons and azaleas.

I was at the Rhododendron Species Foundation in Federal Way, WA, last
week. They had a large, over 20' tall, rhododendron they were
transplanting. The roots ball was less than 8 inches thick. They had
the roots sandwiched between two shipping pallets. That is the first
time I saw how really shallow rhododendron roots are on a very large
plant.

The alkaline areas that I plant in are near the foundation of my home.
The mortar in the stone walls leaches out and tends to sweeten the soil.
I compensate for this as needed by using sulfur powder when I see
chlorotic leaves. It lasts for many years between treatments. On new
homes, the effect be more transient. The soil is OK, but the salts that
are passing through it are the problem. Sulphur is able to handle that
problem.

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