As fertilizer. Coffee grounds placed in the planting hole encourage acid-forming bacteria, boosting the growth of such acid-loving plants as blueberries and evergreens. But take note: once added to compost, the grounds no longer provide acid, as finished compost generally has a neutral pH.
Mix with mulch. Don't use coffee grounds alone as a mulch. Because they tend to cake up, your leftover grounds should always be mixed with dry materials like pine litter or dead leaves.
Use drip grounds instead of boiled grounds; they are richer in nitrogen.
Add heft to tiny seeds, such as those of carrots, lettuce, and radishes. When planting, mix the seeds with a small portion of dried coffee grounds. This will help keep the seeds from clumping, add weight, and give you a better "feel" in your hand.
Grass aid. Repair bare spots on the lawn with a teabag patch. Place a moist used teabag on the spot and sow with grass seed; the bag provides moisture and gradually decomposes. Some gardeners also soak grass seed in liquid tea before sowing it.
Tea mulch. Dump used tea leaves or teabags on the soil in pots or window boxes and cover with a mulch of pebbles or shredded bark. As you water, nutrients from the decomposing leaves will leach down into the soil.
A tea party for plants. Leave a used teabag or tea dregs in water overnight and serve the brew to azaleas, ferns, hydrangeas, and other acid-loving plants. Use only tea that hasn't been mixed with sugar or cream.
Root reservoirs. Put two or three used teabags in the bottom of a pot, placing them on top of the drainage layer of pebbles or shards. The bags will retain water and keep roots moist.