Should You Use Epsom Salt for Hydrangeas

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Epsom salt, known scientifically as magnesium sulfate, is touted by many gardeners and horticulture enthusiasts for its supposed benefits to plant health, including for hydrangeas. This common household item is believed to aid in chlorophyll production, improve nutrient absorption, and enhance the overall vibrancy of flowers.

However, the effectiveness and necessity of using Epsom salt for hydrangeas (and plants in general) is a subject of debate among experts. This article explores the arguments for and against the use of Epsom salt for hydrangeas, backed by scientific understanding and horticultural practice.


What is Epsom Salt?

Epsom salt is a naturally occurring mineral compound composed of magnesium and sulfate, both of which are essential nutrients for plants. Magnesium plays a crucial role in chlorophyll production, the process by which plants convert sunlight into energy. Sulfate, on the other hand, is involved in the creation of proteins, in the process of photosynthesis, and in the activation of enzymes.

The Case for Using Epsom Salt on Hydrangeas

Advocates for using Epsom salt on hydrangeas argue that it provides several benefits:

  • Enhanced Color and Bloom: Magnesium can potentially enhance the color of hydrangea flowers, especially in varieties that produce blue and purple hues, by affecting the pH level of the soil.
  • Improved Photosynthesis: By contributing to chlorophyll production, magnesium from Epsom salt can enhance the plant’s ability to photosynthesize, leading to more robust growth.
  • Nutrient Absorption: It’s believed that Epsom salt can help plants absorb nitrogen, phosphorus, and potassium more efficiently, which are crucial nutrients for plant health.


The Skeptical View

However, many experts caution against the indiscriminate use of Epsom salt:

  • Soil Test First: Before adding any supplements to your garden, it’s advisable to conduct a soil test. A soil test can reveal if your soil actually lacks magnesium. Adding Epsom salt to a garden that doesn’t need it can disrupt the nutrient balance and potentially harm plants.
  • Specific Needs of Hydrangeas: Hydrangeas have specific soil pH requirements for color changes—adding magnesium without understanding its impact on soil pH can inadvertently alter flower colors in an undesired way.
  • Overuse Can Harm Plants: Excessive use of Epsom salt can lead to sulfate toxicity, which can harm the microbial balance of the soil and negatively affect plant health.


Best Practices for Using Epsom Salt

If you decide to use Epsom salt for your hydrangeas, follow these guidelines to minimize risks:

  1. Conduct a Soil Test: Ensure your soil lacks magnesium before adding Epsom salt.
  2. Use in Moderation: Apply Epsom salt sparingly. A recommended dose is about one tablespoon per foot of plant height, mixed with water, applied once a month during the growing season.
  3. Observe Plant Response: Monitor your hydrangeas for any signs of improvement or distress after application. Adjust your care routine based on your observations.


Care Tips for Hydrangeas

Hydrangeas are beloved for their large, showy blooms and are a staple in many gardens. Proper care is essential to get the most out of these beautiful plants. Here are some care tips to help your hydrangeas thrive:

1. Planting Location

  • Light: Most hydrangeas prefer morning sun and afternoon shade, especially in hotter climates. Some varieties can tolerate full sun, provided they get enough moisture.
  • Soil: Plant in rich, porous, slightly acidic soil. Hydrangeas thrive in soil with good drainage and plenty of organic matter.

2. Watering

  • Hydrangeas require plenty of water, especially during hot, dry spells. Water deeply 3 times a week rather than a little every day to encourage deep root growth.
  • Avoid overhead watering to reduce the risk of leaf diseases. Water at the base of the plant early in the day.

3. Mulching

  • Apply a thick layer of mulch (2-3 inches) around the base of the plant to help retain soil moisture, regulate soil temperature, and reduce weed growth.

4. Fertilizing

  • Fertilize hydrangeas once in early spring before the leaves begin to grow. Use a slow-release fertilizer formulated for flowering plants.
  • Avoid over-fertilizing, which can lead to lush foliage at the expense of blooms.

5. Pruning

  • Pruning requirements vary by variety. Generally, hydrangeas that bloom on old wood (last year’s growth) should be pruned just after flowering. Those that bloom on new wood (current year’s growth) can be pruned in late winter or early spring.
  • Remove dead wood and thin out crowded branches to improve air circulation.

6. Managing pH for Color Varieties

  • The color of some hydrangeas (especially H. macrophylla) can be altered by changing the soil pH. Acidic soil (pH below 6) produces blue flowers, while alkaline soil (pH above 7) produces pink flowers. You can adjust the soil pH with aluminum sulfate for blue flowers or lime for pink flowers.

7. Winter Protection

  • In colder climates, protect the roots in winter by applying a thicker layer of mulch. Cover plants with burlap or a frost cloth to shield them from harsh winds and freezing temperatures.

8. Pest and Disease Management

  • Keep an eye out for common pests like aphids and spider mites, as well as diseases like powdery mildew and leaf spot. Treat with appropriate organic or chemical solutions as needed.
  • Ensure good air circulation around the plants to reduce the risk of diseases.

9. Hydration During Blooming

  • Ensure consistent moisture to prevent wilting, especially during the blooming period. Hydrangeas can drink a lot of water when they are in bloom.

10. Patience with Transplants

  • Hydrangeas can take some time to settle after being transplanted. Don’t be discouraged if they don’t bloom prolifically right away. It may take a year or two for them to adjust and begin blooming abundantly.

By following these care tips, you can help your hydrangeas grow healthy and strong, producing beautiful blooms for you to enjoy. Remember, each variety may have its own specific needs, so it’s always a good idea to research the particular needs of your hydrangea type.



What plant should you not use Epsom salt in?

Epsom salt should not be used indiscriminately on all plants, especially those that are sensitive to magnesium or sulfate, or in soils that already have high levels of these elements. Plants that prefer acidic soil conditions or are specifically adapted to low-magnesium environments may not respond well to Epsom salt. Some examples include:

  • Certain Native Plants: Species adapted to specific regional soils with particular nutrient compositions may be negatively affected by the addition of magnesium sulfate.
  • Plants in Magnesium-rich Soils: If your soil test indicates high levels of magnesium, adding Epsom salt can exacerbate the imbalance and potentially harm plants.
  • Sodium-sensitive Plants: While not directly related to magnesium or sulfate, plants sensitive to sodium should not be exposed to softened water often used to dissolve Epsom salt, as it can introduce sodium into the soil.

Always conduct a soil test before applying Epsom salt to determine if your plants actually need it.


How do you mix Epsom salt for hydrangeas?

To mix Epsom salt for hydrangeas, follow these steps to ensure safe and effective application:

  1. Dilution Rate: A general guideline is to dissolve about 1 tablespoon of Epsom salt in 1 gallon of water. This dilution is suitable for small to medium-sized hydrangea plants.
  2. Application Frequency: Apply the solution monthly during the growing season. Early morning is the best time for application to avoid rapid evaporation and to ensure that plants have time to absorb the solution throughout the day.
  3. Method of Application: Pour the diluted Epsom salt solution directly onto the soil around the base of the hydrangea, ensuring it doesn’t splash onto the leaves to prevent potential leaf burn. Alternatively, you can use a foliar spray for a more direct application of magnesium to the plant, which can be absorbed through the leaves. For foliar sprays, use a finer mist and apply in the cooler part of the day.


Does Epsom salt change the color of hydrangeas?

Epsom salt can indirectly affect the color of hydrangea flowers, but it is not the primary agent for color change. The color of hydrangea flowers, especially in varieties like H. macrophylla, is influenced primarily by the pH level of the soil. Acidic soils (pH below 6) tend to produce blue flowers, while alkaline soils (pH above 7) lead to pink flowers. The presence of aluminum ions, more available in acidic conditions, also plays a significant role.



While Epsom salt can be beneficial for hydrangeas in specific circumstances, its use should be informed by a clear understanding of your garden’s soil conditions and the specific needs of your plants. The key to healthy hydrangeas lies not in a single remedy but in a holistic approach to gardening that includes proper soil management, adequate watering, and appropriate fertilization. Before reaching for Epsom salt or any other supplement, consider whether it is truly needed and beneficial for your garden’s unique conditions.


Read More

  1. When to Transplant Hydrangeas? And How to Do It?
  2. How Much and How Often to Water Hydrangeas?
  3. Wilting and Dropping Hydrangeas: Causes and Cures
  4. Transplanting Peonies: Everything You Need to Know
  5. How to Cut Hydrangeas for Vase


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