The Kitchen Scrap That Could Turn Hydrangea Flowers Blue On A Budget

If you've got pretty pink hydrangeas but you're in more of a blue era and want your flowers to match, fear not. You might be able to change hydrangea flowers blue with coffee grounds from your kitchen. There are different varieties of hydrangeas and only some will change the color of their flowers. That's because some varieties are sensitive to changing pH levels in the soil. If you've got bigleaf, mopheads, or French hydrangeas, then you can change the colors from pink or red to blue or purple by making the soil more acidic. Other kinds of hydrangeas are more fixed and less versatile — especially white oakleaf varieties, which won't change colors no matter how acidic the soil.

How does it work? Well, technically, the color of certain hydrangeas depends on how much aluminum the plant absorbs while it's forming the flowers. The more acidic the soil, the more aluminum the plant can take in, and the bluer the flowers get. The less acidic the soil, the less aluminum, and the more likely the flowers remain pink. In order to get blue or purple blooms, you'll likely need to lower the pH below 6, since neutral or alkaline leaning soils will likely produce warm colors like red or pink. Coffee grounds might help lower the soil pH in some cases, so grab some coffee grounds and let's head to the garden to turn those pink blooms blue.

Before sprinkling coffee grounds, it's a good idea to test your soil first to see where the current pH level is. Then, you can work on adjusting it. Fresh coffee grounds tend to have higher acidity levels (with a pH around 5.5) than brewed grounds, which are closer to 6.5. So keep that in mind. Coffee as plant food isn't new, and it can have other benefits as well. These include carbon and nitrogen, two beneficial nutrients to add to the soil.

In order to change the pH of your soil, the best time is before you plant your hydrangeas. Add in fresh coffee grounds in the soil, and then turn it. While adding coffee can temporarily boost acidity in your soil, it'll be harder to maintain long term, as most changes to the soil will be temporary. If you want more of a longer term fix, try adding aluminum sulfate or sulfur to the soil. Keep testing the soil to see if your additions are making a long term difference. Also, remember that if the soil contains a mixture of pH levels, you might end up with several different colors of blooms all in one plant.

Keep in mind, it'll likely take a while for hydrangea flowers to change color, so you may need to be patient and wait several months. Once you make a flower bed more acidic, check out the list of acid-loving plants and shrubs that might be good companion plants for your now-blue hydrangeas.