There are benefits to using coffee grounds on plants and one of those includes using them as a fertilizer. Coffee grounds can add extra nitrogen to the soil so are useful as a supplemental feed when the vines are actively growing. Coffee grounds can either be sprinkled directly around the plants or diluted with water and added as a liquid feed. As well as being able to give pumpkins a nitrogen boost, coffee grounds also keep bugs away and can be used as a control method for slugs and snails.