Coffee grounds are acidic, and roses just so happen to thrive best in slightly acidic soil, but that’s not the only benefit this kitchen ingredient can bring to roses.
Coffee grounds also contain high quantities of nitrogen — one of the main components of fertiliser. They are a natural way to enrich and fertilise plants.
Being a coffee-loving household, we go through a lot of coffee grounds. I would normally just collect them and add them to my compost bin; however, this time I tried adding them straight to my roses.
I sprinkled no more than an inch of coffee grounds directly on the soil around my roses and used a small garden spade to mix them in with the mulch and soil that’s already surrounding the plant.
Working the coffee grounds into the soil is important because if you leave more than a very thin layer on the soil surface, the particles will lock together and form a water-resistant barrier. Rain or irrigation water will simply run off while your roses remain thirsty.
On another one of my roses, I mixed one part coffee grounds in with five parts water before pouring that near the base of my roses.
I avoided getting any of the liquid on the rose leaves, as this can increase the risk of black spot disease.
Once or twice a month is best for spreading leftover coffee grounds beneath roses. Any more frequently and you can risk increasing the soil’s acidic levels and reducing the plant’s ability to absorb essential nutrients.
Gardeners also need to bear in mind that these fine coffee ground particles will wash into the soil during watering or heavy rainstorms, so it’s well worth keeping a note of where they were last added.
Having applied coffee grounds to my roses twice a month since May, I’ve been impressed with the results I’ve seen so far from the flowers.