Van Veen Nursery in Portland, Oregon, reported after using coffee grinds
from Starbucks Coffee House for about 18 months that they were very
satisfied with the results. 1) it helps to aerate their clay soil. 2)
slugs don't like to go through. (So you can see they have both mixed in
and put on top.) It does help to make the soil more acidic. But it does
not replace fertilizer.

They suspect that by making the soil more acidic you are actually
helping the uptake of magnesium. This in turn helps iron uptake and that
helps to make the plant green. So really you are starting a process not
fertilizing. Combine the coffee with horse mature and organic mulch and
watch the amount of fertilizer you use decrease dramatically. As for how
they apply it, when the plant is dry and just before it rains they
sprinkle it on and around. The rain takes it from there. Otherwise they
incorporate into the new beds. No exact rate just cover the top and work
it in. (Courtesy of Vicki at Van Veen Nursery)
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