Blue Hydrangeas: Do Coffee Grounds Work?

The blue hydrangeas are in full bloom this week. The blooms always seem bluer the closer you get to the ocean. I’ve always thought the blue was partly due to our soil and we tend to have cooler, foggy nights.

This spring I decided to test a theory to make the flowers bluer by adding coffee grounds to the base of the roots. To obtain blue hydrangeas aluminum must be present in the soil. You can add aluminum sulfate if your soils lacks it…I’ve also heard theories of throwing a handful of old rusty nails in the soil before planting the shrubs. By adding organic matter such as coffee, vegetable peels, the pH is lowered which helps deliver the aluminum to the plant. (source:

Did I notice a difference? I think I’m lucky that my hydrangeas are naturally a beautiful blue which must mean we have a lot of natural aluminum in our soil. Do they look a tad darker with the introduction of coffee, maybe? I do have more blooms with pure blue rather then a mix of blue/purple tones.

The first and second photos are from this year and the bottom from summer 2011 (more photos here). I don’t notice much of a difference…but a good way to use up excess coffee grounds when you don’t have a compost heap. Either way I think the organic matter is good for the garden, right?

Summer 2012

Summer 2011 (more photos here)

Related Posts:
Blue Hydrangeas From My Garden
Flower School with Chelsea from {Frolic!}
Tip: Grow Mint In A Pot To Reduce Spreading

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