Do coffee grounds affect hydrangea color?

Many swear coffee grounds turn hydrangeas blue. They do acidify a bit. But coffee does not contain the aluminum ions that produce true blue blooms. I tested them for two seasons with minimal results, and dedicated amendments like aluminum sulfate outperform them hugely.

Coffee grounds aren't a substitute for the correct kind of soil amendments. Their effect on pH is short-term and very weak. Aluminum sulfate immediately lowers the pH and supplies aluminum, which hydrangeas crave. Mine shows a much deeper colored bloom since I quit using coffee and switched to aluminum.

Use them sparingly when making compost, mixing them with only a part of the brown material, such as leaves. Depending on what you are trying to avoid in the soil, it can prevent the soil from compacting and, to a certain extent, add brown organic matter at the same time. I add coffee to mine weekly, but my hydrangeas require strong coffee shavings to colour the flowers.

Common coffee grounds mistakes. A biggie! Do NOT put fresh grounds directly onto the soil!! First, compost them for six months. Additionally, restrict applications to a maximum of two cups per month per plant. I burned my gorgeous hydrangeas a few years ago, and they wouldn't budge for months. Finally, I played around with balanced amendments, and they slowly fell into place.

For authentic color changes, follow trusted methods. Aluminum sulfate for blues. Lime for pinks. Test every sixty days. My hydrangeas gleam with compliments from admirers. They didn't spring from coffee experiments but a proper recipe.

Read the full article: Soil pH for Hydrangeas: Color Control Guide