On 12/2/2015 7:44 AM, Bob F wrote:
David E. Ross wrote:
Today, I went to buy gypsum to apply to my clay soil before the winter
rains begin. While I never buy plants at a hardware store or lumber
yard, I do buy tools and supplies at such stores.

I went to a nearby hardware store (about 3 miles from my house) and
took a 40-pound sack of gypsum to the register. With a senior-citizen
discount of 5%, the clerk said that it would be $12+change. I left
the sack at the register and drove to a favorite nursery about 12
miles away. There, I bought a 50-pound sack of gypsum for under $9.

That is correct: 25% more gypsum for 25% less money. Both were 92%
CaSO4 (calcium sulfate).

What effects do you see from applying gypsum? Is it anything obvious? Are repeat
application useful?



My soil is very heavy clay. Gypsum supposedly reacts with the clay to
make it porous and thus improve drainage and root growth. I apply a
generous amount annually in the late autumn around my camellias,
azaleas, and liquidambar tree, which seem to thrive. Every two years, I
apply it throughout my garden, using about 250 pounds. Also, when
planting a new plant or bulb, I stir a small amount of gypsum into the
planting hole.

--
David E. Ross
Climate: California Mediterranean, see
http://www.rossde.com/garden/climate.html
Gardening diary at http://www.rossde.com/garden/diary