A neat feature of hydrangeas is the ability to change the flower color. However, not all varieties of hydrangea change color. Some kinds of hydrangea only come in white. Other varieties can be blue, pink, red, or purple, and it’s possible to affect those colors by influencing the alkaline levels or acidic quality of the soil where the hydrangeas grow.
Which Varieties of Hydrangea Can Change Color?
Bigleaf hydrangeas, especially lacecap and mophead (H. macrophyllis) change color. Some bigleaf hydrangeas include Endless Summer Twist-n-Shout, Endless Summer BloomStruck, Endless Summer Crush, Cityline Paris, Cityline Berlin, and Cityline Rio. Additionally, mountain hydrangeas (H. Serrata) can have their color altered by the soil contents.
How To Change Hydrangea Color
Maybe you bought those blue hydrangeas you have always wanted, planted them, and the following year they bloomed, big beautiful...pink flowers. Huh? Why did this happen? Where did your BLUE flowers go? Can you get them back with the process of hydrangea color change?
Yes...if you’re patient, you can change hydrangeas from pink to blue or blue to pink.
Do You Want Blue Hydrangeas or Pink Hydrangeas?
Generally, it is more difficult to change pink hydrangea flowers to blue than it is to change blue flowers pink. So you blue lovers may require a bit more patience and dedication. Check out the huge selection of hydrangeas at our plant nursery.
The most basic thing to understand about changing hydrangea color from pink to blue or from blue to pink is soil pH. Acidic soil changes some hydrangeas so they grow blue flowers. Alkaline soil changes hydrangeas to pink. Neutral soil, on the other hand, will allow your hydrangea to revert to a color in the middle. If you want to know how to change your hydrangeas to purple, neutral soil is the answer.
How long does it take to change hydrangea color? It can take weeks or even months to years to adjust the soil pH and therefore adjust the color of your hydrangea plants. So, it takes careful planning and patience. But it’s worth the wait!
Follow these steps on how to change hydrangea color, to change your hydrangeas to blue or back to pink.
The first step in hydrangea color change is to check your soil pH to know where you stand. You can pick up a soil test at garden centers or home improvement stores. The ideal pH for pink blooms is around 6.0. The optimal pH for blue blooms is 4.5 to 5.5. If your pH is higher than 7.5 this may be a fight you won’t win. Soil this high in pH tends to have free calcium carbonate or marl which make it very difficult to lower the pH.
Turning your hydrangea flowers pink is achieved by adding lime to your soil. Apply garden/agricultural lime by following the recommended dose for the product you purchase. The dose can vary depending on your current pH and the type of soil you have. Sandy soils require less lime than clay soils. Generally applying about one cup per plant once per year is safe. Sprinkle the lime all around your plant on the soil as far out as the dripline. Use a rake to combine lime and the top layer of soil, but be gentle to avoid harming your plant’s roots. The optimal time to apply the initial dose of lime is in early spring or fall. However, you can add the lime anytime. Even if you are already seeing flowers you may be able to see a hydrangea color change before blooming season is over. Especially with the reblooming varieties of hydrangea that have a long flowering season.
Turning your hydrangea flowers blue can be as simple as applying aluminum sulfate, elemental sulfur, or our Espoma organic soil acidifier. Aluminum sulfate is a chemical compound that reduces the pH of your soil. Elemental sulfur is pure sulfur which is an element that acidifies your soil. You know - the periodic table from high school science class - yep, those elements. Both aluminum sulfate and elemental sulfur work by making aluminum available to your hydrangeas. This reaction acidifies the soil and your plant produces blue flowers. Elemental sulfur is the cheaper choice, but aluminum sulfate works faster so it is usually the preferred choice for most gardeners.
For established plants, apply 1lb (2 cups) of aluminum sulfate or 1/6lb (1/3c) elemental sulfur around your hydrangea bush. Be sure to check the directions on the package you choose as there can be variations in products and directions. A direct topdress to the soil around your hydrangea plant covering the entire rootzone out to the dripline seems to be the most effective and easiest method versus a water dilution. The optimal time to apply the initial dose is late winter or early spring.
Some people report success using coffee grounds to change the color of their hydrangeas. Coffee grounds, in theory, carry enough acid to increase the acid in your soil to change your hydrangeas to blue hydrangeas. This method may work, and coffee grounds break down into the soil well, so there’s no harm in trying it. However, if you want to give yourself better odds of results, you might consider a product specifically designed to increase the acidic balance of your soil.
Pat down the soil to ensure the incorporation of the lime or sulfur. Water deeply and thoroughly. This is key to getting the chemical processes going and encouraging the hydrangea color change to take hold. So don’t skip this step! Be sure to rinse any lime or sulfur off your plant. The leaves don’t love lime or sulfur.
Test your soil after a few months. You don’t want the soil pH to go above 6.4, if you’re trying to get pink flowers. At this pH, hydrangeas cannot absorb iron and may become chlorotic. You want it to be between 4.5 and 5.5 if you’re aiming for blue flowers. If your pH isn’t where you want it or the hydrangea color change hasn’t happened yet, don’t get discouraged. This isn’t unusual. Apply another dose of lime or sulfur depending on the result you’re aiming to achieve. If you need more acid because you want pink flowers, add more lime. If you need more alkaline soil to get blue flowers, add more sulfur.
Hopefully, you will see your soil pH in the appropriate range, but if not repeat the application again until you reach the desired acidity or alkalinity.
If you are seeing purple hydrangea flowers instead of pink flowers or blue flowers, you are on the right path and can just apply another dose.
Pink Perfection - Tips from the Pros
Hand watering may affect your efforts especially if you have soft water. Soft water tends to be low in pH or acidic. A good solution, if you have soft water, is to catch rainwater and use that to water your hydrangeas.
If your pH goes too high, add an iron supplement when you fertilize your plant in spring. If your soil test shows elevated aluminum choose a fertilizer with high phosphorus (the middle number). Phosphorus helps prevent the absorption of aluminum which is just what you need to achieve those pretty pink blooms.
If you have tried everything with no success, you can always grow your hydrangea bushes in pots. This controlled environment is an easy way to get your flowers the color you want. To adjust the pH of the planting mix cut the lime dose in half for container-grown hydrangeas.
Check out our large selection of hydrangeas in our online garden center. Learn more about hydrangea types and how to grow hydrangeas here.