Myth or Fact: Can Vinegar Make Hydrangeas Turn Blue?

Blue hydrangea flowers are the envy of gardeners everywhere. There are so few plants out there that produce true blue flowers. Luckily we have the hydrangea that not only produces blue flowers but very large blue flowers as well.

Unfortunately, not everyone’s true blue hydrangea dreams come true. This could be for a number of reasons. Most likely, you’ve not chosen the right type of hydrangea, but it could have to do with your soil pH. 

Because this soothing hue is so sought after, the internet is flooded with myths and tricks about how to achieve the bluest of the blues. So, can you successfully use vinegar to turn your hydrangea flowers blue? If you enjoy these D.I.Y.  life hacks, read along to find out if this nifty trick is truly all it’s hyped up to be. 

The Short Answer

Diluted apple cider vinegar has been known to acidify garden soil, which in turn will turn your hydrangeas blue. Of course, with any home gardening remedy, it is not quite black and white. There are some risks, and hitches along the way. I believe that this remedy could work, but I also believe that it would not be permanent and could be potentially damaging if it is overused.

The Long Answer

Hydrangea macrophylla, or bigleaf hydrangeas, are sensitive to the pH of garden soil. If your garden soil is alkaline (pH of 6.5 or higher), your hydrangeas will have pink flowers. Where if your soil is acidic (pH of 5.5 or lower), the blooms will be blue. 

Aluminum is the element that is responsible for turning your flowers blue, and it is readily found in most soils. However, the more acidic the soil is, the easier it is for your plants to absorb the aluminum. When soil is sweet or alkaline, the aluminum will not be as available to be taken up by the roots of your hydrangeas. This is why people often use aluminum sulfate to help turn flowers blue; the sulfur component reduces the soil pH and makes it absorb the aluminum better.

Before adding a soil additive, it is really important to test your soil to make sure you aren’t adding anything that is unnecessary to your gardens. Doing so could damage your plants. 

Vinegar itself is an acidic solution with a very low pH of 2.5. The addition of vinegar to soil has been shown to lower its pH. 

Know Your Species

Before you try adding anything to your soil, make sure you are growing the right species of hydrangea. Hydrangea macrophylla or bigleaf hydrangeas are the only type of hydrangea that are sensitive to the pH of the soil. When growing any other species, your flowers cannot change colors. 

If you are certain you are growing a bigleaf hydrangea, there is one small speed bump you need to cross before you can begin your color-changing journey. If the variety you’ve chosen is white, you cannot alter these flowers. White hydrangeas will always be white hydrangeas. 

Vinegar Soil Test

This is a fun science project with kiddos, but it is just as fun and informative to do by yourself. You will need some vinegar, water, baking soda, and two clear containers, such as mason jars.

Collect a scoop of garden soil and dump it into your containers. It is helpful to take this soil sample from the garden where you hope to blue your hydrangeas. You will have the best results if you take this soil sample from a few inches below the soil surface. 

Add soil to both of your containers. In the first container, add ½ cup distilled water to your soil and mix it around. Next, add ½ cup vinegar to the mixture. If your soil mixture begins to bubble or fizz, you have alkaline soil.

In the next container, add ½ cup of distilled water and ½ cup of baking soda to your soil. Mix these ingredients around. If this mixture bubbles, the soil is acidic. The stronger the bubbling, the more acidic the soil is.

Of course, the results of this test will not give you specific results the way that a lab would, but it is enough information to get you headed in the right direction. 

How To Do It

Fill a large watering can with water from your hose and apple cider vinegar to the watering can. You are looking for a ratio of 20 parts water to 1 part vinegar. Just eyeball it. Remember, less is more. Mix it around.

Use the watering can to apply the mixture. Water the plant as you normally would. Make sure you are applying this mixture to the soil around your plant and not on top of the plant. Diluted vinegar may be safe, but undiluted vinegar can harm your plants. Better to be safe than sorry!

Be Careful!

Be very slow while adding this mixture to your garden. Start with a low rate. If you notice that you are having some success, you can always go back and apply it again. 

Vinegar can damage the leaves of your hydrangea. It is really important to make sure that this mixture is diluted enough to avoid any damage. Take your time and make sure that the mixture is only hitting the roots of the plant. 

Over time, too much vinegar may damage your gardens. Horticultural vinegar, with its high levels of acidity (15% or higher), has been known for a long time to be an excellent natural weed killer. This works by spraying vinegar onto the green herbaceous surface of your weeds.

While household vinegar is much less potent at 3% to 5%, imagine what could happen if you suddenly have a bunch of vinegar building up in your soil over time. While the vinegar will eventually neutralize, you might have a problem for quite a while until it does!

What Else Can I Do?

Many products on the market are specifically meant to acidify the soil and blue up your hydrangea blossoms. These products usually contain the main ingredient of aluminum sulfate. If you are opting to use a ready-made product, use the application rate found on the product label to ensure your plants are getting the right amount!

There are many other methods of turning your hydrangeas blue, and many of them are anecdotal at best and harmful at worst. Garden myths like using pennies or rusty nails to change bloom colors are just that, garden myths.