Is It Actually Possible to Change the Color of Hydrangeas Using Coffee?

Gardening may not seem like an art form to the uninitiated, but truly clever gardeners understand that there are many tricks to achieving success in this often tricky trade. While some flowers require more care and precision, others, like hydrangeas, present many different opportunities for customization. They can be crossbred into different colors through advanced techniques, but can you really change the color of hydrangeas with coffee?

According to Garden Design, there is some truth to the rumors that say coffee can change the color of hydrangeas. We’re not suggesting that you go and pour coffee on your plant's roots or anything, but some gardeners have reportedly used coffee grounds in the soil to help change their hydrangeas to a bluer hue.

Coffee grounds have been used as a successful fertilizer and composting component for many years. According to HGTV, coffee grounds make the soil more acidic, which raises the pH of soil. They also possess a high nitrogen content, which makes them ideal for composting. Once broken down, this added nitrogen ultimately improves soil’s ability to hold water. 

According to Gardenista, most species of hydrangea will change color depending on the pH level of their soil, though it appears as though white hydrangeas are the exception to this rule. If the soil is more acidic, then the hydrangeas can more easily absorb aluminum from the soil. This added aluminum will make pink hydrangeas turn blue. It will also keep your blue hydrangeas from turning pink.

If your soil is more alkaline, your hydrangeas will be pink or even purple. According to Garden Design, adding lime or eggshells to the soil will ensure a pinker color, while adding aluminum sulfate, pine needles, or coffee grounds can give your hydrangeas the blues. 

Garden Therapy recommends using both pine needles and coffee grounds in your compost to raise the pH of your soil. Like coffee grounds, pine needles will raise the overall acidity of your soil, but usually not enough to make any noticeable change if applied directly. Your best bet is to incorporate them into your backyard compost and use the resultant fertilizer to improve soil health all-around. 

According to World of Garden Plants, eggshells don’t just make it more difficult for your hydrangeas to absorb aluminum and turn blue; they also provide an added dose of nitrogen and calcium to improve growth overall. Like coffee grounds, the best way to ensure absorption is to crush the eggshells into a fine powder and spread them around the soil at the base of your hydrangeas’ roots. 

Ultimately, we can't tell you how to color your hydrangeas. What we can do is suggest that if you are going to incorporate coffee, eggshells, or pine needles into your gardening routine, you try doing it the right way. Creating a backyard or kitchen compost bin is a great way to become more zero waste. Composting will enable you to repurpose your food scraps into something meaningful, and perhaps within the space of a season, something beautiful.