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Hydrangeas are big leafy plants and are quite popular in gardens and landscapes. The plants produce bright flowers which add fragrance and aesthetic appeal to your home. The plants typically bloom in pink, purple, blue, or white colors.

The PH of the soil influences the coloration of the blooms. Pink or red blossoms typically appear in more alkaline or neutral soils, while blue blooms appear in acidic soils. One major way of achieving blue blooms is raising the PH of the soil by burying rusty nails near the roots of the hydrangea.

How do the Rusty Nails Turn Hydrangeas Blue?

Remember that the PH of the soil is the primary determinant of the color of your blooms. The soil PH is the measure of the acidic or alkaline content of the soil. Every plant has a unique PH that favors the growth of the plant. The Hydrangeas species blossom more in acidic soils, allowing the plants to absorb aluminum available in the soil which significantly influences the color change.

If the soil is alkaline with a PH averaging 7.5, the hydrangeas will not absorb the intrinsic nutrient, aluminum. In such a case, your plants will not turn blue.

How Does a Rusty Nail Work?

A rusty nail interferes with the PH of the soil and makes it more acidic. Thus, rusty nails buried near the roots of the plant will change the color of your plants. You can also achieve equivalent results when you add aluminum sulfate to the soil instead of rusty nails. But aluminum sulfate is quite expensive to purchase; rusty nails are the best cheaper alternative.

How to Bury Rusty Nails?

  1. The first step is removing any surrounding clutters, such as leaves that lie around the hydrangea plant.
  2. Ensure you dig the hole away from the roots of the plant. If you damage the roots, your plant will wilt. Once you identify that the area does not have any roots, use a trowel to dig a hole approximately six inches deep and an average of 10 inches from the plant.
  3. Place the rusted nail in the hole, then cover it with soil. The nail will gradually increase the soil’s acidity and help your plant take up aluminum from the soil with ease.
  4. For maximum results, dig other holes six inches apart and place other rusted nails. After that, cover the area with adequate mulch.

Key Points about Hydrangea Color Change

Pink hydrangea is most affected by soil PH and will rapidly change to beautiful blue hues. It is quite straightforward to turn pink blooms to blue than turning blue blooms to pink. Also, white hydrangeas such as the Oakleaf and Pee Gee are rarely affected by the soil PH and rarely turn to blue.

The best way to ensure that your plants retain the blue hues is by constantly measuring the PH of the soil. You can use a PH test strip to determine the PH of the soil. If you note your soil is alkaline, you can add more rusty nails, altering the PH.

Also, remember when you bury the rusty nails adjacent to the hydrangea, you should not expect instant results. The changing of PH from alkaline to acidic is insidious and will take a while before the blooms change to blue. However, the effects are long-lasting, and you should ensure you increase the soil’s acidity in the following year.

Changing the Color of Hydrangeas in Containers

The plants in containers are more manageable than those in the garden. When planting this plant, you can use soil with a lower PH by adding substances such as aluminum sulfate. Also, you can add rusty nails to the soil to increase the acidity of the soil. However, be very cautious so that you don’t damage the roots of the plants.


The best way to turn your hydrangeas blue is by burying rusty nails adjacent to the plant. To ensure your plants flourish maximumly, you must also incorporate other care and maintenance tips such as watering and growing the plants in partial shades. Lastly, ensure you regularly prune your plants to ensure they blossom to maximum and retain the right size and height without occupying a large part of your garden.