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.
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. To lower your pH, add garden sulfur or aluminum sulfate to your soil. To raise the pH, use ground lime.
A high pH makes the soil more alkaline, which will color the hydrangea blooms pink. A low pH makes the soil more acidic, which turns the hydrangea blooms blue. You can change the color of some varieties of hydrangea by adding aluminum sulfate to make the flowers more blue, or by adding dolomite to make them pink.
Baking soda is one of the recognised ways to change the color of hydrangeas. It will alter the pH level in the soil and therefore change the bloom color. White hydrangeas are primarily grown in a neutral soil and to keep them that way, you must transplant them into a soil similar to what your plant has been grown in.
It is easier to change blue flowers to pink than to change pink flowers to blue, and some cultivars are more prone to color variability than others. We recommend waiting until the plant is at least 2 years old to give it time to recover from the shock of its original planting.
Hydrangea Care Tips
- Water at a rate of 1 inch per week throughout the growing season.
- Add mulch underneath your hydrangeas to help keep the soil moist and cool.
- Apply fertilizer based on your specific hydrangeas.
- Protect against pests and disease by choosing cultivars with resistant traits.
If you're looking to harness the benefits of coffee grounds related to improving the quality of the soil, you can use them in composted form 2-3 times a year. If you want to alter the pH of the soil, you may need to use them more often, scattering them over the soil of your hydrangea.
You should deadhead throughout the blooming season to keep your hydrangeas looking their beast and encourage new flower growth. However, stop deadheading hydrangea shrubs in mid to late fall, leaving any spent blooms in place.
It is much easier to change a hydrangea from pink to blue than it is from blue to pink. Changing a hydrangea from pink to blue entails adding aluminum to the soil. Changing from blue to pink means subtracting aluminum from the soil or taking it out of reach of the hydrangea.
First of all, not all hydrangeas produce blue flowers. These types of hydrangeas have the interesting ability to change the color of their blooms based on the chemistry of the soil. When grown in alkaline soil, the bloom colors are pinker. When grown in acidic soil, the bloom colors are bluer.
If your soil is more acidic, pH around or less than 5.5, then your blue hydrangeas stay blue or bluer. White hydrangeas stay white. Don't even try to alter the soil pH to change the color.
"Too much direct sunlight, especially in the afternoon, will cause the flower color to fade quicker than normal," she explains. "Your hydrangea should be planted in a spot that is protected from the hot afternoon sun, but still receives the cool morning sun."
Simply layering the coffee grounds on top of the soil is quicker but may result in an ugly pile of mold that looks messy and smells unpleasant. Alternately, dump your coffee grounds into your compost bin and add the compost as part of your twice-yearly fertilizing ritual for your hydrangeas.
Sprinkle elemental sulfur over the soil.In order to keep your hydrangeas blooming in blue, elemental sulfur should be sprinkled over the soil around the shrub to lower the pH to below 5.5. The exact amount of elemental sulfur required will vary, depending on the soil type and how much the pH needs to be adjusted.
Best grown in rich, medium moisture, well-drained soils in part shade. Tolerates full sun only if grown in consistently moist soils. Soil pH affects the flower color of most cultivars except white (blue in highly acidic soils and lilac to pink in slightly acidic to alkaline soils).
Timing of Application. Changing the acidity of soil can take more than just one season, although if you want blue flowers on your hydrangea, the time to add soil acidifier for hydrangeas is in the spring before flower buds form.
Adding dried coffee grounds to the soil around hydrangeas increases the acidity of the soil, which boosts the blue-producing capabilities of the hydrangea and the ability to absorb aluminum from the soil. Monitor the pH level of the soil over time with a pH test kit; a range of 5.2 to 5.5 is best for blue blooms.
Or to transform established hydrangeas into blue beauties, apply 2½ cups of Organic Soil Acidifier. Spread evenly around the hydrangea out to its drip line, or the widest reaching branches. Then, water well. Repeat every 60 days until you've got the perfect color for you.
Banana peels also make a great fertilizer for hydrangeas. Use the peels from two or three bananas per plant. Chop the peels into small pieces and bury them around the base of each plant. Using banana peels as a fertilizer for your hydrangeas will also help to repel aphids.
So the answer is a definite maybe. The Epsom Salt Council () recommends one tablespoon per nine square feet, applied to the root zone of the shrubs at two- to four-week intervals.
