How To Make Hydrangeas Blue With Pennies

If you’ve ever wondered how to make hydrangeas blue with pennies, you’re in the right place. This simple and effective method is a favorite old-time gardening trick that many swear by. It’s a budget-friendly way to try and influence the stunning color of your bigleaf hydrangeas. Let’s look at how it works and the steps to try it in your own garden.

First, it’s crucial to know that not all hydrangeas can change color. This trick only works on Hydrangea macrophylla, the bigleaf variety. These are the shrubs that produce those classic, round mophead or lacecap blooms. If your hydrangea is white, no amount of pennies will change it. The color change is all about soil chemistry.

Why Hydrangeas Turn Blue: It’s All About Aluminum

Blue hydrangea blooms need two things: acidic soil and available aluminum. In acidic soil (low pH), aluminum is released from the soil particles. The plant’s roots can then absorb this aluminum. Once inside the plant, it interacts with the pigments in the blooms, creating those beautiful blue and purple shades.

If your soil is more alkaline (high pH), the aluminum stays locked up. The plant can’t absorb it. In that case, even a hydrangea with the genetic potential for blue will bloom in pink or red tones. So, our goal is to gently acidify the soil and provide a bit of aluminum.

This is where the penny method comes into play. The idea is that old pre-1982 pennies, which are made of 95% copper, can help. As the penny oxidizes in the damp soil, it releases tiny amounts of copper ions. This can slightly lower the soil pH over a very long time. However, the effect is minimal and incredibly slow. The real helper in this method isn’t the penny itself—it’s what you add with it.

What You’ll Need for This Method

30-50 old, dull pennies (minted before 1982).
A handful of used coffee grounds.
Some organic matter like peat moss or composted oak leaves.
A small trowel or garden shovel.
A bucket for mixing.
Watering can.

Step-by-Step Guide to Using Pennies

Follow these steps carefully for the best chance of success. Timing matters, so it’s best to start in early spring as the plant wakes up.

Identify Your Hydrangea: Make absolutely sure you have a bigleaf hydrangea (Hydrangea macrophylla). Check the leaves and bloom shape if your unsure.
Gather Your Pennies: Collect older, copper pennies. You can tell them apart because they are a darker, duller brown color compared to the shiny, zinc-based pennies made after 1982.
Prepare the Area: Gently loosen the soil around the base of your hydrangea. Go out to the “drip line,” which is where the outermost leaves reach. Be careful not to damage any major surface roots.
Mix Your Amendments: In your bucket, combine the coffee grounds and organic matter. Coffee grounds are slightly acidic and can help lower pH a tiny bit while adding organic material.
Add the Pennies: Scatter your old pennies evenly around the loosened soil area. Then, sprinkle your coffee ground mixture over the top of them.
Cover and Water: Lightly cover everything with a thin layer of soil or compost. Then, give the area a thorough, deep watering. This helps start the process of integrating the materials into the soil.

What to Expect After Applying the Penny Method

Patience is key. You will not see a change overnight. The penny method is a very gradual, mild approach. It might contribute to soil acidity over many months or even years. You may notice a slight shift in bloom color toward the violet or lavender spectrum after a full growing cycle. For a more pronounced and reliable blue, most gardeners need to take additional steps.

Boosting Your Results for Vibrant Blue Blooms

To truly make your hydrangeas a vibrant blue, you need to support the penny method with proven techniques. Here’s what you can do alongside it.

Test Your Soil pH: This is the most important step. Buy a cheap soil test kit from a garden center. You need to know your starting point. For blue blooms, you’re aiming for a soil pH between 5.2 and 5.5.
Apply Aluminum Sulfate: This is the most effective product for blue blooms. It acidifies the soil and adds aluminum. Follow the package directions carefully, usually applying in spring and again in fall. Never over-apply, as it can harm roots.
Use Acidifying Fertilizers: Choose a fertilizer labeled for acid-loving plants like azaleas, rhododendrons, or blueberries. These help maintain the lower pH your hydrangea needs.
Mulch with Acidic Materials: Use pine needles, shredded oak leaves, or peat moss as mulch around your plant. As they break down, they can gently help acidify the soil.

Common Mistakes to Avoid

When trying to change hydrangea color, a few errors can set you back or hurt your plant. Avoid these common pitfalls.

Using Only Pennies: Relying solely on pennies will likely lead to dissapointment. They are a supplemental trick, not a complete solution.
Changing Soil Too Quickly: Dramatic pH swings stress the plant. Always make adjustments gradually over seasons.
Applying Near the Trunk: Always apply amendments out at the drip line, where the feeder roots are. Putting material right against the stem can cause rot.
Forgetting to Water: Consistent moisture is vital for hydrangeas, especially when trying to move nutrients like aluminum through the soil.

Caring for Your Blue Hydrangeas

Once you start seeing those blue tones, maintenance is straightforward. Continue to test your soil pH every year or two. Reapply aluminum sulfate or an acidifying fertilizer as needed based on the test results. Keep the plant well-watered during dry spells, and prune it correctly—right after blooming—to ensure next year’s flower buds aren’t removed.

Will This Method Work on Potted Hydrangeas?

Yes, you can use a version of this method in containers. It’s actually easier to control the soil environment. Use a potting mix for acid-loving plants as your base. You can add a few pennies to the bottom of the pot or mix them into the top layer of soil. For potted plants, using an aluminum sulfate solution according to label directions is often the most effective and fastest route to blue blooms.

FAQ: Your Hydrangea Color Questions Answered

How long does it take to turn hydrangeas blue with pennies?

Using just pennies, it could take multiple growing seasons to see any slight change, if at all. It’s a very slow process. For faster results, combine pennies with aluminum sulfate.

Can I use new pennies instead of old ones?

New pennies (post-1982) are mostly zinc with a copper plating. They will not have the same potential effect as the solid copper old pennies and are not recommended for this method.

Why are my hydrangeas still pink after trying this?

If your soil pH is still too high (alkaline), the aluminum—whether from pennies or other sources—remains unavailable. Test your soil pH. You likely need a stronger acidifier like elemental sulfur or aluminum sulfate to lower the pH enough.

Do coffee grounds alone make hydrangeas blue?

Coffee grounds can slightly acidify soil, but they do not add aluminum. They can help create the right acidic conditions, but you usually need an aluminum source as well to achieve a true blue color.

Is the penny method safe for the soil?

In the small quantities used, old copper pennies are generally considered safe. They release copper extremely slowly. However, never use large amounts, as excessive copper can become toxic to plants and soil life.

The idea of learning how to make hydrangeas blue with pennies is a charming piece of garden folklore. While pennies alone are unlikely to create a dramatic shift, they can be part of a broader, natural approach to garden care. By understanding the science behind the blue—acidic soil plus aluminum—you can use the penny trick as a starting point. For the most stunning sapphire blooms, support it with a soil test and targeted amendments like aluminum sulfate. With a little patience and the right know-how, you can encourage your hydrangeas to show off their beautiful blue side.