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Coffee Tips

Will Coffee Grounds Turn Hydrangeas Blue?

If you brew coffee every day, you know it adds up to a lot of grounds. That’s because most coffee drinkers take at least 3 or 4 cups of coffee a day. Most coffee drinkers have now found ways of recycling, upcycling, and downcycling these coffee grounds.

coffee grounds blue hydrangeas

A common use for coffee grounds is gardening, particularly in growing flowers such as Hydrangeas and Roses. They are often used by flower farmers to encourage the growth of blooms and to brighten or change their color as in the case of Hydrangeas.

Coffee grounds are also added to compost heaps to make organic fertilizer. Some farmers also use them to feed worms which are essential for boosting soil value in worm bins.


Why Do We Use Coffee Grounds in Gardening?

A significant reason for recycling coffee grounds is to keep them away from dumps where they can contribute to global warming. If we allow coffee grounds to get to landfills, they will contribute to greenhouse gas emissions by releasing methane into the atmosphere.

Using coffee grounds in gardening is a much better option. They are rich in minerals such as nitrogen, chromium, potassium, and phosphorus that can improve the quality of your flowers and plants. Coffee grounds also;

  • Attract worms that aerate the soil and decompose organic soil matter.
  • Acidify neutral or alkaline soil to benefit plants that thrive in such environments.
  • Keep ants that transport dangerous aphids away from your garden.
  • Discourage slugs from feeding on the flowers, bulbs, and leaves of your plants.
  • Prevent cats and other pets from digging into flowerbeds.
  • Encourage plants to absorb minerals such as Aluminum from the soil


Do Coffee Grounds Affect the Color of Flowers?

One of the best-kept secrets about coffee that applies to gardening is how it can change the color of flowers. Of particular interest is its ability to turn Hydrangeas blue. How does this happen?

Hydrangeas are globe-like flowers that pop up in gardens during late spring and early summer. These flowers are usually white, pink, or blue in color. Their color depends on the pH level of the soil they grow in.

Coffee grounds can change the color of Hydrangeas due to their acid content. The increased acidity helps hydrangeas to absorb aluminum from the soil, which prompts the plants to grow blue-colored flowers. Some hydrangeas even turn purple.

Soil with a pH of less than 6 will encourage hydrangeas to produce deep blue flowers, while that with a pH of more than 7 will result in pinkish blossoms.


How to Add Coffee Grounds to Your Garden Soil

Before you use coffee grounds to fertilize your garden soil, measure its pH. That will enable you to check whether using coffee grounds will enhance the soil’s pH to a level ideal for turning your hydrangeas blue or not.

You can test your garden soil pH by using a store-bought soil pH kit. If that is not available, try the DIY method, which only requires the use of baking soda, vinegar, and two containers.

Pour a handful of your garden soil into each container and add half a cup of water. Next, add a half cup of baking soda into one container and a half cup of vinegar into the other.

If the soil in the container with vinegar fizzes, your soil is alkaline. You can boost its acidity with coffee grounds to encourage your Hydrangeas to produce blue blooms.

But if the soil in the container with baking soda fizzes, your soil is acidic. Showing there is no need to fertilize your soil with coffee grounds. The acidity in the soil will boost the growth of blue Hydrangeas even without augmentation.

Lack of or little fizzing in both containers signifies that your soil is neutral. That kind of soil is likely to produce a mix of pink and blue flowers or purple flowers. But using coffee grounds to make it acidic will increase the chances of turning your hydrangea flowers blue.

You should also plant the right Hydrangeas in your garden for your color-changing experiment. French Hydrangeas and Mountain Hydrangeas are best for this experiment.

The color of your Hydrangeas also matters. Generally, purple, pink, or blue Hydrangeas can change color. But, if you use white or ivory-colored Hydrangeas like Peegees, Oakleafs, and Annabelles, your experiment will fail. The most they can turn is a little pinkish when they age.


How to Use Coffee Grounds to Change the Color of Your Hydrangeas

Using coffee grounds as a natural fertilizer is as easy as making fertilizer tea. That requires you to scoop 2 handfuls of grounds in five gallons of water and leave them to soak overnight. It’s similar to creating cold brew but for your plants.

You can also use leftover coffee straight from your coffee maker as Hydrangea fertilizer. Just dilute the coffee and drench your soils with it to encourage the growth of healthy blue flowers. Some people also sprinkle dry coffee grounds over their garden soil for the same effect.

The ideal time to augment your soil with coffee grounds or fertilizer tea made using coffee grounds is in late fall. Sprinkle or irrigate the area around the flowers and then work the fertilizer into the soil by mixing it in with a gardening trowel. Avoid using too much coffee in your fertilizer to keep from burning your plants.

It takes some time for coffee grounds to encourage hydrangeas to produce blue flowers. But if you patiently fertilize your soil with coffee grounds 2 or 3 times a year, your flowers will grow the bluest Hydrangeas in due season.



Using coffee grounds as an organic fertilizer is much better than using commercial fertilizers. Coffee grounds are organic materials that are unlikely to damage your soil unless used in excess.

Take the use of coffee grounds in your garden as an experiment. It may boost the growth of your flowers or not.

But there is a general consensus among gardeners that coffee grounds can turn hydrangeas blue. Try adding them to some of your flowers and see how it goes.

If it doesn’t work, you can always throw your grounds into the compost bin for use in other parts of your garden.


Also read How Do Coffee Grounds Help Hydrangeas?