Why Are My Blue Hydrangeas Turning Purple

This traditional favorite is a must-have in any garden, and new cultivars have made hydrangea cultivation simpler than ever.

Generally speaking, blue or lavender-blue hydrangea flowers are produced by acidic soil, which has a pH lower than 6.0. Pinks and reds are encouraged by alkaline soil, which has a pH above 7.0. The blossoms turn purple or bluish-pink at a pH of 6 to 7.

Add aluminum sulfate or garden sulfur to your soil to reduce pH levels. Use ground lime to increase the pH. To ensure that the pH of your soil is within the desired range, retest it according to the instructions on the product you’re using.

Fungal Disease

Cercospora leaf spot, a prevalent leaf fungus in these plants, can be identified by the presence of purple dots on hydrangea leaves. Although spotted leaves can shed early, weakening the plant and limiting the number of viable buds, plants are rarely killed. Usually beginning at the plant’s base, the tiny purple to brown patches grow outward and upward when water splashes the spores onto adjacent leaves. The type of hydrangea involved determines the specific spotting patterns.

By removing fallen leaves and hydrating your hydrangea at the base, you can stop cercospora from spreading. In a densely packed hydrangea bush, opening the canopy by pruning up to one-third of the branches will improve air circulation and hinder the spores’ ability to germinate. Azoxystrobin, chlorothalonil, mancozeb, myclobutanil, or thiophanate-methyl should be used at intervals of 14 days if cercospora is severe and pervasive.

Phosphorus Deficiency

When hydrangea leaves become purple, the plant may be trying to notify you that there isn’t enough phosphorus in the area to support it. In their haste to alter the hue of their hydrangeas’ flowers, gardeners occasionally unintentionally cause the pH to go so low that other chemical substances bind phosphorus. The inability of bound phosphorus to be utilized by plants deprives them of essential nutrients.

Examine your soil. Alkali soils with pH levels above 7.0 may bind phosphorus with calcium or magnesium, while acidic soils with pH levels below 6.0 frequently allow aluminum to bind the element. The initial step in releasing phosphorus from your soil is to adjust the pH, but if this doesn’t work after a few weeks, you’ll need to fertilize your hydrangea with phosphorus.

Weather’s Influence

The color of hydrangea leaves can also be affected by the weather, resulting in extensive purple discolouration. When the growing season is about to finish, cool conditions may cause the plant to go into dormancy early, allowing the purple color of the leaves to emerge as the green chlorophyll factories stop producing them for the year.

Purple discolouration might also result from frost damage. When the leaves are dry, remove the severely harmed ones, but keep the somewhat harmed ones until new leaves emerge.

How are blue hydrangeas kept that color?

Although most plants may grow in a variety of soils, others require particular kinds of soil to thrive. Rhododendrons, azaleas, and other ericaceous plants require acidic soils in order to thrive. The soil in your garden must be acidic if they flourish there or in the gardens nearby. Rhododendron leaves turning yellow or disappearing from the area indicate that your soil is likely alkaline. In addition to affecting what you may grow, your soil type can also affect some plants’ leaf and blossom colors; hydrangeas are a well-known example.

Some hydrangea cultivars grow pink or red in alkaline soil and blue or purple in acidic soil. Therefore, if you plant a beautiful blue lacecap or mophead hydrangea in your garden and your soil is neutral to acidic, it will continue to produce blue flowers every year. Even if it was clear blue when you got it, it will flower purple-red or pink if you plant it in alkaline soil the next year.

It is challenging to keep beautiful blue blossoms alive in the open ground, but it is doable if you grow it in a pot; hydrangeas make wonderful topics for pots and containers. Select a pot that is attractive and big, at least 40 cm (15 cm) in diameter. Vitax Ericaceous Compost is the best growing medium for it; plant it there. If you consistently feed your hydrangea, it will thrive on this fertilizer that is specifically made for rhododendrons, azaleas, and other lime-hating plants.

Even though the growing medium begins out being free of lime, repeated watering in places with hard water tends to make it more alkaline. Therefore, add Vitax Hydrangea Colourant, a powder containing aluminum that you may mix with the compost, to ensure that your hydrangea stays truly blue. Each spring, you can also incorporate a small amount into the soil’s top layer and add it to the can when watering your plant.

White hydrangeas, incidentally, don’t change color depending on the type of soil, but they can blush pink in the light.

Feeding and watering

In pots, containers, and during dry spells in the open ground, regular watering is necessary since hydrangeas detest dry environments. When you plant your hydrangea in a bed or border, add lots of garden compost or farmyard manure, and make sure to water well both before and after planting.

The presence of food in the soil is necessary for hydrangeas to grow and produce flowers, even if they are not very demanding plants. In the open ground and in pots and containers, Vitax Conifer and Shrub Fertilizer should be used annually. This is ideal for acid-loving plants and won’t change the hydrangea’s color.

Do hydrangeas turn blue from coffee grounds?

  • Maintain low amounts of phosphorus, moderate levels of nitrogen, and high levels of potassium in the soil in order to make sepals bluer.
  • Maintain high levels of nitrogen and moderate amounts of phosphorus while adding garden lime to the soil to give sepals a pinker hue.
  • This should be completed in late autumn or early spring, well before flowering.

Can coffee grounds be used to change the color of hydrangeas?

Some gardeners claim that adding coffee grounds to the soil helped them successfully dye their hydrangeas blue. The soil becomes more acidic thanks to the coffee grounds, which makes it easier for the hydrangea to absorb metal. Fruit peels, grass clippings, peat moss, and pine needles are also believed to have a comparable impact.

Can eggshells be used to change the color of hydrangeas?

Crushed eggshells might be a good approach to grow pink hydrangeas. Eggshells will gradually degrade and lessen the acidity of your soil, which will make it more difficult for hydrangeas to absorb metal.

How do I make blue hydrangeas with vinegar?

To adjust the soil’s acidity and colour their hydrangeas blue, many gardeners add vinegar to their watering can. However, if you use Hydrangea Blue, a liquid fertilizer that yields blue flowers, you’ll probably get greater results.

Will hydrangeas become blue in vinegar?

In alkaline soil, hydrangea blossoms will be pink; in acidic soil, they will turn blue.

If great French wine is not properly stored, it will turn into vinagre, which we translated into vinegar in English. Vinagre is a combination of the Old French words “vin” (wine) and “aigre” (sour).

There are certain advantages to using vinegar in gardening, especially apple cider vinegar. A few vitamins and minerals are present in apple cider vinegar because it is only fermented apple juice. However, vinegar’s 5% acidity makes it an excellent remedy for any acid-loving plants, including rhododendrons, azaleas, northern bayberries (Myrica pensylvanica), blueberries, and cranberries. Conifers and pecans are two examples of trees that favor acidic soil.

Along with feeding your garden plants, you may use apple cider vinegar on houseplants that prefer acidic soil, such gardenias and camellias. Some houseplants thrive in acidic soil.

You must measure the pH of your soil before fertilizing it or adding any amendments. The soil pH test determines how acidic or alkaline the soil is.

A very acidic pH of 3 corresponds to a very alkaline pH of 10. Seven is regarded as the neutral pH. Your soil’s acidity or alkalinity has an impact on a number of chemical processes, including which nutrients are locked up in the soil and which nutrients are available to your plants.

There are several garden plants that do well in acidic soil, despite the fact that the ideal pH range for most plants is between 5.5 and 7.5. It is not surprising that many plants that thrive near pine trees, such as blueberries, azaleas, and rhododendrons, also prefer acidic soil because pine needles make soil acidic.

The best apple cider vinegar to put on plants is raw, organic apple cider vinegar that hasn’t been filtered. Ensure “with the mother” is written on the label.

The mother is a brown mass that is composed of yeast and bacteria that were left behind during fermentation.

Apple cider vinegar should never be poured directly over plants since it will damage them. Of course, undiluted vinegar will work well if your purpose is to kill plants like weeds in walkways, sidewalks, or driveways.

Use apple cider vinegar diluted with water (20 parts water to 1 part vinegar). Water the plants at the base of them. The vinegar-and-water mixture might burn the leaves, so try to avoid getting it on them.

The ability to transform the color of hydrangea blossoms from pink to blue is another trick apple cider vinegar has up its sleeve. In alkaline soil, hydrangea blossoms will be pink; in acidic soil, they will turn blue.

Give the acid-loving plants a treat by combining apple cider vinegar and water. Or abruptly switch the hue of your hydrangeas from pink to blue. Oh, and what about pearls dissolved in vinegar?

Pearls were dissolved in vinegar and consumed by Cleopatra to display her wealth, likely making the acidic beverage the most expensive beverage ever. Speaking of bittersweet.

Paul Barbano, who lives at Rehoboth Beach, writes about gardening there. You can write to him at PO Box 213 in Lewes, Delaware 19958.

Will the color of my blue hydrangea last?

First off, like rhododendrons, azaleas, Japanese maples, pieris, etc., hydrangeas prefer and thrive in acidic soil. Your hydrangea’s change in color is caused by the pH of your soil. There are several levels of soil acidity and alkalinity in between.

Your soil’s health affects the health of your plants. The pH of the soil has an impact on and determines how hydrangeas change color.

Your hydrangeas will be pink or pinker if your soil is more alkaline. Clay is typically found in alkaline soils, which range in pH from to 79. Your blue hydrangeas will remain blue or get even bluer if your soil has a pH of around or less than 5.5.

If you know your soil is more alkaline than neutral, you should use soil acidifier or garden sulfur before planting blue hydrangeas. You’re unsure. If you’re unclear about the pH of your soil, you can search online for a soil lab in your state or purchase a cheap soil pH test kit or pH meter.

My blue hydrangeas are fading—why?

Enfield claims that placing hydrangea flowers in direct sunshine is a proven technique to hasten the natural fading of the colors of those flowers. The hue of the flowers will fade more quickly than usual if they are exposed to too much direct sunshine, especially in the afternoon, she says. “Your hydrangea should be placed in a spot that receives the cold morning sun while being shielded from the hot afternoon sun.”

Are hydrangeas kept blue by rusty nails?

I’ve heard a lot of misconceptions and partial truths regarding hydrangea colors throughout the years (this is for Hydrangea macrophylla i.e. Mophead and Lacecap Hydr.).

In our garden center, I frequently get asked why the blossoms on hydrangeas change blue or pink. The majority of gardeners prefer blue flowers, which might be more difficult to grow than pink flowers, especially if your soil is uncooperative.

Many people can claim that iron causes flowers to turn blue and that adding rusty nails to the soil will have the desired effect. But that is a fiction, and it is completely false! The problem is a little more intricate than that!

Which fertilizer is ideal for blue hydrangeas?

When purchasing fertilizer, check the labels to see how much nitrogen (N), phosphate (P), and potassium are present (K). A general-purpose, balanced fertilizer such a 10-10-10 N-P-K or 12-4-8 N-P-K is typically best for hydrangeas. Consider using a fertilizer with additional phosphorus if you want your hydrangea blossoms to be bigger and more numerous.

Since phosphorus is the middle element, fertilizer with the formula 10-20-10 will do. Choose a slow-release granular fertilizer with the designation “bloom boost” if you’re looking into it because it might also include more phosphorus.

Does blue hydrangea soil need to be acidic?

For hydrangeas to change from pink to blue, the soil must be acidic and contain salts of either aluminum or iron.

We all learned in chemistry classes in school that distilled water has a neutral pH of 7. However, in horticulture, a neutral pH is typically categorized as 6.5. Any soil with a pH below 6.5 is considered acidic, and any soil with a pH above 6.5 is considered alkaline. A pH testing kit can be used to check the pH of your soil, and Greenshutters Nurseries & Garden Centre has these on hand. The inexpensive pH meters that are available are often not precise, so I do not advise using them. Often, seeing surrounding gardens and the local plant life is a simpler approach. It’s likely that your soil is acidic if nearby Rhododendrons, Camellias, and Pieris are flourishing in the soil.

Peaty or sandy soils are typical of acidic soils. Clay soils are typically not highly acidic. Chalky soils have a high pH. By incorporating Irish moss peat or ericaceous compost, you can increase the acidity of your soil. Ericaceous compost has an acidic pH range of roughly 5.0 to 5.5, while regular multifunctional compost has a pH range of 6.0 to 6.5.

Irish moss peat is particularly useful for mulching since it has a pH of about 4.0, which is much too acidic for most plants to thrive in. However, when combined with neutral or alkaline soil, it lowers the pH of the soil. Once a year, mulch with Irish moss peat and let the worms to work the peat into the soil to maintain the acidity of the soil around a plant.

As an alternative, hydrangeas can be grown in containers. Although hydrangeas can thrive in both multifunctional and ericaceous compost, it is recommended to plant them in the latter if you want them to turn blue.

If your soil is deficient in aluminum or iron salts naturally, you can easily increase them by putting Hydrangea Colorant into the soil. People claim that adding rusty nails to the soil or compost will turn hydrangeas blue; however, as I have never tried it, I am unable to confirm if this is true or false. On the other hand, Hydrangea Colorant is a combination of Iron Salts and Aluminium Sulphate. When potting or planting, it can be added to the soil. For established plants, you can also dissolve the Hydrangea Colorant in water and give your hydrangeas a weekly drink during the growing season (March to September). Your light pink kinds will become blue if you do this, while your dark pink varieties will turn mauve-blue.

Grow your hydrangea in neutral or alkaline soil, though, if you want it to stay pink.