I'm trying the coffee grounds as mulch around plants that are prone to mealys and scale, but I have to wonder if those alkaloids Would also harm the bees and hummingbirds that feed on the nectar. It may be "organic", but it is still systemic, and the bugs still feed on the plant until it kills them. I'm thinking using it as a spray would be safer, though not nearly as convenient.
Has anybody studied this?
