What will Epsom salts do to hydrangeas?

Answered by Tom Adger

Epsom salts, also known as magnesium sulfate, can have several effects on hydrangeas. One of the main effects is an increase in the amount of magnesium in the soil. Magnesium is an essential nutrient for plants, and it plays a crucial role in various physiological processes.

When it comes to hydrangeas, the pH of the soil determines the color of the flowers. As mentioned earlier, a pH below 6 is ideal for blue flowers, while a pH above 6 encourages pink ones. The addition of Epsom salts can indirectly influence the flower color by affecting the pH of the soil.

Epsom salts are water-soluble, and when they dissolve in water, they release magnesium and sulfate ions. The magnesium ions can compete with other cations in the soil, such as calcium and potassium. This competition can lower the pH of the soil, making it more acidic. As a result, the soil becomes more suitable for blue hydrangea flowers.

However, it’s important to note that the effect of Epsom salts on flower color is not immediate. It takes time for the soil pH to change, and the plant needs to take up the magnesium ions and transport them to the flower petals. This means that if you want to change the color of your hydrangeas using Epsom salts, you need to apply them well in advance, preferably in the fall or early spring before the growing season.

In addition to affecting flower color, magnesium also plays a role in overall plant health. It is an essential component of chlorophyll, the pigment responsible for photosynthesis. Magnesium deficiency can lead to yellowing of the leaves and poor plant growth. By adding Epsom salts, you can supply the plant with an extra source of magnesium, potentially improving its overall health and vigor.

It’s worth mentioning that while Epsom salts can be beneficial for hydrangeas, they should be used in moderation. Excessive use of Epsom salts can lead to an imbalance of nutrients in the soil and may have negative effects on plant growth. It’s always best to conduct a soil test to determine the nutrient levels and pH of your soil before adding any amendments.

To summarize, Epsom salts can increase the amount of magnesium in the soil, which can indirectly influence the color of hydrangea flowers by affecting the soil pH. They can also provide a supplemental source of magnesium, promoting overall plant health. However, it’s important to use Epsom salts in moderation and consider the specific needs of your hydrangeas and soil conditions.