It’s been about two weeks now, and the results are pretty conclusive.  Coffee grounds just don’t work well as potting soil on their own.  I guess the people that put together the commercial potting soil really do have a decent product.

I’ve been saving my coffee grounds for a couple of weeks now and have quite a lot of this stuff.

Even if coffee doesn’t make good potting soil, maybe it can be a good additive.  I’ll have to think up a new experiment to test it.