10 Tips To Change Hydrangea Color

To change color, you will want to know that not all hydrangea types are going to respond to a change in the pH of the soil. Bigleaf hydrangeas, and Hydrangea macrophylla, are likely to be the ones that change color, so they are the best choices.

Specifically, 'Endless Summer' and 'Nikko Blue' cultivars are sensitive sports varieties, which will bloom anywhere from blue to pink, depending on the soil's acidity or alkalinity. Knowing the hydrangea type will help in determining whether or not soil condition alteration will work in changing flower colors.

An important part of determining the color of the flowers in your hydrangea is testing the pH of your soil. Blue flowers have been known to grow in acidic soils with a pH below 6, as aluminum becomes more available under such conditions.

On the other hand, pink flowers are more common in alkaline soils with a pH above 7 since the amount of aluminum reduces at higher pH levels. In neutral soils, hydrangeas can manifest in purple flowers, basically a mix of both the blue and pink shades. 

Acidifying the soil by adding soil amendments like aluminum sulfate or elemental sulfur will promote blue hydrangea flowers. In addition, aluminum sulfate reduces pH quickly and provides some aluminum, which intensifies the blue color.

Elemental sulfur, on the other hand, works more slowly by converting the soil to sulfuric acid. These substances should only be added in small quantities in a measured amount, according to the package instructions, lest they over-acidify the soil, causing harm to plants.

For pink hydrangea flowers, the soil pH must be raised using alkalinity. A garden lime increases the pH of the soil. It works by reducing acidity in the soil, hence making aluminum less available; aluminum can also give a blue color to the plant.

The more alkaline the soil gets, the more it shifts to produce pink blooms of hydrangeas. Application of garden lime must be done gradually to avoid sharp changes in the pH of the soil, which might directly impact the healthy growth of plants.

Using coffee grounds or pine needles can serve as a natural way to decrease soil pH and foster blue flowers on a hydrangea plant. Since coffee grounds are only slightly acidic, the mixing will have a gradual action on the soil, decreasing its pH.

As pine needles break down, they contribute to the acidity of the soil with the release of organic acids that act further to acidify it. Just mix them into the soil around your shrubs, and that is what will help to get the right bloom color for blue hydrangeas.

Crushed eggshells may be a natural method to raise the pH of the soil and produce pink hydrangea flowers. As they decompose, eggshells release calcium carbonate into the soil, raising its pH by counterbalancing acidity.

It is this shift toward a more alkaline environment that makes less aluminum available to the plant, hence pink flowers. Just crush the eggshells, mix them into the soil around your hydrangeas, and watch the magic unfold. 

Stable soil moisture enables healthy plants with good hydrangea colors. Hydrangeas want uniform moisture to stay fit. Large fluctuations in water availability tend to stress the plants out, and so their capability for nutrient uptake becomes reduced.

Be sure to keep the soil moist but not sogging wet because root rot may set in. Regular watering allows the plants to develop strong blooms that hold good color, mostly during dry seasons. Adequate moisture management promotes overall plant health.

If blue-colored hydrangea is the goal, one should avoid phosphorus-rich fertilizers since high phosphorus in the fertilizer may restrain the plant's absorption of aluminum. With ample phosphorus, it will compete with aluminum in uptake and result in less intensity of the blue hues.

Instead, choose low-phosphorus and high-potassium fertilizers. These fertilizers will provide the necessary nutrients without interfering with the availability of aluminum which maintains the correct blueness of color in your hydrangeas.

Additions of organic matter, such as compost or peat moss, can be mixed into the soil to acidify it, favoring blue blooms of the hydrangea. Organic matter is decomposed, releasing acids into the soil and improving its structure.

Through the regular addition of these natural amendments, it is possible to gradually bring down the soil pH over time, making more nutrients available for uptake and creating the ideal conditions for the hydrangea to achieve blue coloration.

One can grow companion plants that are acid-loving in the planting area to maintain a lower pH in the soil, thus providing favorable conditions for the hydrangea. Acid-loving plants that include blueberries, azaleas, and rhododendrons may contribute acidic soil through their roots and leaf litter.

While they grow, they can help sustain the desired acidic conditions by creating a perfect environment for hydrangeas and eliminating constant pH adjustments. The approach nurtures an acid condition for the soil, is stable, and is sure to offer bright blue hydrangea flowers.

Hydrangeas belong to the category of popular flowering plants with large, gorgeous flowers and different colors. Their origin is from Asia and the Americas; they belong to the family Hydrangeaceae and are quite famous in gardens and landscapes as merely decorative plants.

The flowers may be blue, pink, white, or purple, depending on the pH of the soil. They are usually in large conspicuous clusters. It is a varied-form plant, from small shrubs to large bushes, which prefers well-drained soil with a portion of shade; therefore, it is easy to grow and cultivate.

What Determines Hydrangea Color?

Two interdependent factors dictate whether hydrangea blooms are pink or blue: the availability of the micronutrient aluminum to the plant and the soil's pH level. The more aluminum the plant can absorb from the soil, the closer the pigment molecules in the bracts move together, resulting in a blue color.

Conversely, when less aluminum is absorbed, the pigment molecules spread out, turning the flowers pink. The amount of aluminum available to plants is controlled by the soil's pH. While most soils have sufficient aluminum, it may not be accessible to the plant if the soil pH is too high (alkaline).

Here's how it works;

• Acidic Soil: At pH below 6.0, the acidic soil increases the availability of aluminum, which is then absorbed by the plant to form blue or purple blooms.
• Neutral to Alkaline Soil: In neutral to alkaline soils, at pH 6-7 or higher, aluminum becomes less available to the plant, and the blooms are pink or red.

Which Types of Hydrangeas Change Colors?

Before you decide on changing the color of your hydrangea you must ensure that they are the right fit because not all species of hydrangea can change color based on the pH of the soil and the availability of aluminum in the soil. The most common types of hydrangeas that have the color changing ability are: 

Bigleaf Hydrangea

This is the most common variety. It has two subcategories, mainly including:

• Mophead Hydrangeas: These plants have big, rounded clusters of flowers.
• Lacecap Hydrangeas: These are flat and feature delicate flower clusters with a central core of small, fertile flowers surrounded by larger sterile flowers.

Mountain Hydrangea (Hydrangea serrata)

This shrub is similar to bigleaf hydrangeas but is usually smaller and more cold-hardy. These hydrangeas will also alter color based on soil pH.

Other varieties of hydrangeas, including Hydrangea paniculata, or the panicle hydrangea, Hydrangea arborescens, or smooth hydrangea, and Hydrangea quercifolia, or oakleaf hydrangea, do not normally have a dramatic color change regarding soil pH.

Incorporate Dolomitic Lime 

To achieve hydrangeas' pink or blue flowers, one needs to change the pH levels in the soil. Add dolomitic lime to your soil, which will raise the pH and make it less acidic.

Not only does dolomitic lime adjust the pH in the soil, but it also applies these essential calcium and magnesium nutrients to create healthy plants, which might end up being color blooms. Be careful when you apply precisely per instructions and avoid excess application that might hurt plants.

Use Alkaline Fertilizers

Another approach would be to make use of the alkaline fertilizers formulated for raising or maintaining the soil pH in extremely alkaline soils. Such fertilizers are designed to foster an elevated level of pH—an ideal environment for hydrangeas that form pink flowers in more alkaline soil.

Their regular use will ensure the reaching and maintenance of the intended soiL levels of pH, which can lead to optimal flower color expression.

Add Wood Ash 

Wood ash is a natural material that is easily available to help raise the pH of your soil. You can dust a thin layer of wood ash around your hydrangea plants and mix it into the ground for this purpose.

Wood ash is especially beneficial since it is full of potassium and other nutrients that will work on improving the health of the plant while encouraging pink blooms.

Add Vinegar Solution 

If you prefer blue hydrangeas, you can make your soil more acidic by adding a solution with vinegar. Mix 1 cup of vinegar in 1 gallon of water and add it sparely to your plants. Do this a few times a year since its excessive use can result in extreme acidity, which is bad for your hydrangeas.

Use Sphagnum Moss 

Finally, adding sphagnum moss in the soil or for top-dressing acidifies the soil, hence creating favorable conditions for blue blooms. Sphagnum moss is naturally acidic but also acts in retaining moisture, hence favoring hydrangeas that do well in a little more acidic conditions.

These techniques, when applied rightly, will ensure control of the soil's pH to obtain the colors of blooms you want from your hydrangea.

Be patient after amending your soil, as changes in pH can take several weeks, months, or even up to a year to reflect in your hydrangeas' flower color. The more significant the adjustment needed to achieve your desired color, the longer and more challenging the process will be.

During this period, continue testing the soil and make further amendments if necessary. Adjusting soil pH is a gradual process and won't occur immediately, making the color change feel like an ongoing challenge.

For blue cultivars of bigleaf and mountain hydrangea, fertilize once in spring with a formulation for acid‐loving plants. Phosphorus in the soil tends to bind aluminum so that it isn’t readily available for the plant. Use a fertilizer low in phosphorous (the middle number in the content analysis) such as 12‐4‐8 to encourage the production of blue flowers.

For other types of hydrangeas, use a general-purpose fertilizer, at recommended rates on the package. Incorporate dry fertilizer into the top 2” – 3” of soil and water thoroughly.

When to Fertilize to Change Color?

To control hydrangea color, fertilize in early spring when the plant first shows signs of new growth. Use a fertilizer that is formulated to produce your preferred flower color. If pink blooms are desired, then a fertilizer high in phosphorus with a more alkaline pH should be used, or lime can be added to the soil to raise its pH.

If blue blooms are wanted, a fertilizer that acidifies the soil should be used or aluminum sulfate applied to lower the pH. A second application in mid-summer can further support color development. Do not fertilize late in the season to avoid stimulating new growth that may be damaged by frost. 

Fertilizers to Change Hydrangea Color

While choosing a fertilizer for hydrangea, one must take into consideration their needs and the color of bloom they desire. The following options will help in this matter:

• Balanced Fertilizer: This would be a fertilizer with equal parts nitrogen, phosphorus, and potassium, like 10-10-10 or 20-20-20. This type of fertilizer will support the general health of the plant and give rise to robust growth with good flowering.
• Hydrangea-Specific Fertilizer: There are hydrangea fertilizers especially designed to give this plant the appropriate balance of nutrients. These can often work more efficiently to bring out blooms and create overall good health in the plants.
• Phosphorus-Rich Fertilizer: For pink blooms, add fertilizer higher in phosphorus. This will increase the pH level of the soil, which pink hydrangea flowers prefer.
• Acid-Loving Fertilizer: If you want to induce blue blooms in plants, you need to look for fertilizers that are acid-loving, if not based on sulfur or ammonium sulfate. This type of fertilizer will reduce the pH of the soil to a more acidic level, favorable for blue flowers.
• Organic Options: Another such would be organic fertilizers like compost or well-rotting manure. These provide slow-release feeds and structural improvement to the soil, hence providing long-term health and bloom quality to plants.