How to Bury Rusty Nails in Soil Around Hydrangea Plants

Hydrangea macrophylla, also known as hydrangea, are very sensitive plants. They are one of the few types of plants that change the colors of their blooms based on the acid content in their surrounding soil. Burying rusty nails near the roots of the plant will turn hydrangea flowers gradually from pink to blue. When you tire of the blue flowers, removing the nails and placing lime in the soil will change them back to pink.

Soil pH probe tester
Gardening gloves
Trowel
Rusty nails

Instructions

- 1
  Insert the probe of the soil pH tester into the ground about 6 inches from your hydrangea plant. Follow the instructions to get an accurate reading of the pH levels in the soil. Hydrangea flowers turn blue in soil that measures between 5.2 and 5.5 on the scale. Soil that is between 5.6 and 6.0 will only require two to three nails to reach the desired level, while a measurement of more than 6.0 requires five to six nails.
- 2
  Put on your gardening gloves to protect your hands. Dig a 6-inch deep hole 4 to 5 inches from the base of the hydrangea on one side, being careful not to slice any of the root system in two. Deposit half of the nails in the bottom of the hole and cover with soil. Repeat on the other side of the plant with the rest of the nails.
- 3
  Test the soil again two weeks later to ensure that the soil is at the desired level of acidity. If the soil is too acidic and measures below 5.2, the plant may be damaged. Remove half of the nails from each side of the plant. Add more nails to soil that is still too alkaline to change the flower color.

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