Nitrogen not only helps keep the cut flowers vibrant and lush for longer but also discourages the growth of microbes that can foul the water and create an unpleasant odor.
For optimal results, change the water every other day as the grounds will eventually dissolve. Monitor the water quality closely, and if it becomes cloudy, it's best to start anew.
You can also mix coffee grounds with sugar and lemon juice to create a homemade flower food that functions just like commercial packets, ensuring the flowers stay fresh for longer.