Coffee grounds are a good source of nitrogen and are great to add to your compost pile, but if you put them on top of your mulch it can get crusty and block water from reaching your soil. That's probably a bigger risk than adding too many nutrients.

Go for it at any time of the year & it will enrich the soil without being too much from your 1 cup filters with grounds. Worms will find 'em & improve the soil for you! I've been teased for the huge quantity of used St*rbucks grounds smelling up the yard at times for weeks, but its made such a noticeable difference that my family forgives me and still brings home the St*rbucks bags. I never say no to coffee grounds.

Those 3 prong hand cultivators work great to work them into the soil surface to prevent crusting over or acquiring a moldy look. Any filters sticking out after the gentle cultivator action could be tucked in further by hand.

What doesn't work is using as mulch around lower growing plants like strawberries or leafy lettuces unless you also top dress them with dried grass clippings or straw. In our rainy climate the splashing up of coffee grounds is a bother.

If in the vegetable garden during growing season I prefer to tuck here & there under larger plants or mix it with the dried grass clippings before spreading.

Any empty garden space is fair game for the big bags of grounds plus shredded leaves from anytime after fall harvest through spring planting mixing it up now & then on nicer days to prevent rain puddling because on cold wet days I just dump the whole garbage bag spreading out just a bit as the bag empties.

In spring I just rake it back a bit before planting or if too thickly layered will remove to another garden location.

If I'm planning a lasagna garden project I will save up bags for a few weeks to add as just one part of the layer or layer it on as I acquire materials. It really works well!