Some gardeners report success in turning their hydrangeas blue by applying coffee grounds to the soil. The coffee grounds make the soil more acidic, allowing the hydrangea to more easily absorb aluminum.
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.
Start adding coffee grounds to the soil surrounding your hydrangeas in late fall. Sprinkle them around your hydrangeas, but be sure to work them into the soil to help eliminate any off-putting smell. You do not need to do this process often–just two to three times per year should be sufficient.
For true blue flowers, the hydrangeas need to be grown in acidic soil with a pH of 5.5 or lower. For pink flowers, the plants need neutral to alkaline soils (pH 6.5 and higher). For purple blooms (or a mix of blue and pink flowers on the same plant), the pH of the soil must be between pH 5.5 and 6.5.
Hydrangeas change colors based on the soil pH levels. Coffee grounds can change soil by making it more acidic, which causes hydrangeas to turn blue, while more alkaline soils make blooms pink.
Generally speaking, acidic soil, with a pH lower than 6.0, yields blue or lavender-blue hydrangea blooms. Alkaline soil, with a pH above 7.0, promotes pinks and reds. With a pH between 6 and 7, the blooms turn purple or bluish-pink.
There is one more trick up the apple cider vinegar sleeve: You can actually change the color of hydrangea flowers from pink to blue. Hydrangea flowers will be pink in alkaline soil, but change to blue in acidic soil. So, mix up some apple cider vinegar and water, and give all the acid-loving plants a treat.
However, many times it's easy to turn those pink imposters back to blue, should one so desire. Simply squeezing a few lemons or limes over the plant somewhat raises the acidity level of the soil, consequently turning the blooms from pink to blue.
Many gardeners add vinegar to their watering can to change the acidity of their soil and turn their hydrangeas blue.
In most cases, the grounds are too acidic to be used directly on soil, even for acid-loving plants like blueberries, azaleas and hollies. Coffee grounds inhibit the growth of some plants, including geranium, asparagus fern, Chinese mustard and Italian ryegrass.
Water at a rate of 1 inch per week throughout the growing season. Deeply water 3 times a week to encourage root growth. Bigleaf and smooth hydrangeas require more water, but all varieties benefit from consistent moisture.
Water your hydrangeas in the morning before the heat of the sun is strong enough to quickly evaporate soil moisture. Try to avoid watering at night, which can encourage mold and mildew as the moisture sits through the cool night. Water your hydrangeas through the growing season as well as in late fall.
If you're growing hydrangeas, use coffee grounds to affect their color. Coffee grounds add extra acidity to the soil around hydrangeas. On a chemical level, this increased acidity makes it easier for the plant to absorb naturally occurring aluminum in the dirt. The effect is pretty blue clusters of flowers.
This common household item is surprisingly effective at helping perk up plants and brighten blooms. For hydrangeas specifically, adding baking soda helps the plant retain more moisture in the roots. When this happens, the result is bigger blooms with more vibrant colors that last longer than they would otherwise.
No. Baking soda will not make any color changes to your hydrangeas and is safe for plants of all types, including those that you are trying to keep a specific hue on them (like blue flowers).
To change hydrangea flowers from blue to pink, you need to remove the aluminum from the soil. The only way to do this is to add garden lime to the soil to help raise the pH.
The color of the hydrangea is determined by the acidity level of the soil it's planted in. Soil with an acidic pH will typically produce blue flowers, while alkaline soil produces pink blooms. To ensure your hydrangeas turn out their most vibrant shade, you'll need to adjust your soil's pH to a strongly acidic level.
Large hydrangea plants can take months to convert their color, so you might not see the results until next year's bloom. Sometimes you'll see some flowers change color and others not, so be patient and amend the soil as needed.
Pink-and-red hydrangeas, however, perk up their color in a soil with a higher pH—one that's less acidic and more alkaline—of about six. To lower the aluminum or acid content in your soil, spread wood ashes or limestone over the ground and use a hoe or tiller to work it into the soil.
Add lime to the soil for pink blooms; add aluminum sulfate for blue blooms. The amount of lime or aluminum sulfate needed depends on the soil composition.