One of the most popular garden hacks to reuse coffee grounds for plants and flowers is by adding it to your compost
The grounds decompose quickly, providing nitrogen to the soil and improving aeration
Aim for no more than 10 to 20 percent ground coffee in the composition of your compost.
Too much acid in the compost can prevent it from heating up enough to properly decompose.
To keep a good balance, add four times the amount of dry material, such as leaves, each time you add coffee grounds to the compost pile.
Don't forget the vermicompost! Worms, such as red wigglers, love used coffee grounds, and the grounds also help to keep the moisture up in the environment.
While not plants, but rather part of the fungi kingdom, growing mushrooms is an out-of-the-box garden hack to use up your coffee grounds.
Considered agricultural waste, mixed with either straw or hardwood chips, used ground coffee is a fantastic substrate