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Epsom Salt Controversy

GardenWise has received a number of differing opinions on the subject of using Epsom salt in the garden.

There seem two schools of thought: do use it in moderation and don’t use it except in very specific circumstances.

After further research, we are inclined to no longer recommend the use of Epsom salt in single-family gardens.

Before applying any treatment to soil, it’s important to first test your soil. Magnesium deficiency is usually only found in cases of intensive cropping or during extended periods of rainfall, as it can leech away quickly from top soil.

Since tree roots are an important source of magnesium, mulching with leaves will offer soil a good source of the mineral along with complementary nitrogen, which aides in a plant’s absorption of magnesium.

Find more information about magnesium deficiency in soil in the excellent research paper by Dr. Linda Chalker-Scott, PhD, associate professor and extension urban horticulturist at Washington State University Puyallup Research and Extension Center.

Are the leaves on your tomato or pepper plants turning yellow? Want more blooms on your rose bushes? Wondering why your lawn is looking brown? These problems may be the result of a lack of magnesium in soil, prohibiting roots from absorbing much needed nutrients. Give your foliage and flowers a boost by using Epsom salt.

Magnesium and sulfur, the main components of Epsom salt, can help to restore essential nutrients to soil. Although magnesium and sulfur occur naturally in soil, they can be depleted over time. Epsom salt can also help with seed germination and the production of chlorophyll, which plants use to transform sunlight into food. In addition, Epsom salt can aid in the absorption of phosphorus and nitrogen, two of the most important fertilizer components.

Epsom salt's advantage over other soil additives is its high solubility. When distilled, and especially when applied as a spray, Epsom salt can be quickly absorbed by the roots. But unlike most commercial fertilizers, which build up in the soil over time, Epsom salt is not persistent so it can't be overused. 

Eight ways to use Epsom salt in the garden:

  1. Lawns: Apply three pounds for every 1,250 square feet with a spreader or dilute in water and apply with a sprayer.
  2. Houseplants: Use two tablespoons per gallon of water; feed plants monthly.
  3. Tomatoes and Peppers: Use one tablespoon per foot of plant height per plant; apply every two weeks to keep the leaves from yellowing.
  4. Roses: Use one tablespoon per foot of plant height per plant; apply every two weeks. Also scratch 1/2 cup into soil at base to encourage flowering canes and healthy new basal cane growth. Soak unplanted bushes in one cup of Epsom Salt per gallon of water to help roots recover. Add one tablespoon of Epsom Salt to each hole at planting time.
  5. Shrubs (evergreens, azaleas, rhododendron): Use one tablespoon per nine square feet. Apply over root zone every 2-4 weeks.
  6. Trees: Apply two tablespoons per nine square feet. Apply over the root zone 3 times annually.
  7. Garden Startup: Sprinkle one cup per 100 square feet. Mix into soil before planting.
  8. Flowering plants: Put one tablespoon of Epsom Salt into one gallon of water. This mixture helps to force blooms.

For more information on Epsom salt and its many uses go to