Epsom salt, also known as magnesium sulfate, is a mineral compound that some gardeners use to help plants grow. While it may seem like an easy way to give your plants a boost, there are several reasons why you should avoid using Epsom salt in your garden.
What is Epsom Salt?
Epsom salt gets its name from the mineral springs in Epsom, England, where it was originally discovered. Its chemical makeup is magnesium sulfate heptahydrate. In its purest form, Epsom salt appears as a white crystalline powder and dissolves easily in water.
For gardening purposes, Epsom salt is sometimes touted as a “magic elixir” that can help produce healthier, more abundant vegetables, flowers, shrubs and even lawn grass. It is also said to deter pests. However, science-based evidence for these claims is limited and the benefits of using Epsom salt in the garden remain unproven.
Reasons to Avoid Using Epsom Salt in the Garden
1. Minimal Impact on Plant Growth
Manufacturers of Epsom salt products for gardening often claim that it provides vital nutrients that boost plant growth and yields. However, research does not back up these assertions.
While magnesium is an essential nutrient for plant growth, calcium and sulfur levels typically have a much bigger influence on plant development. Most soils already contain adequate magnesium supplies for healthy plant growth. As such, applying additional magnesium in the form of Epsom salt does not translate into any measurable improvements in plant size, crop yield, or quality.
The exceptions are acidic soils and soils with very high levels of calcium. In these cases, magnesium may be less available to plants. Even then, however, adding magnesium amendments based on soil test results is a more targeted approach than general Epsom salt applications.
The bottom line is that Epsom salt may help if your soil is deficient in magnesium, but for most gardens its impact on plant growth is negligible.
2. Raises Salt Levels in Soil
Excess salt in soil can damage plants and reduce yields. While Epsom salt contains valuable magnesium, it is still essentially just a soluble salt. When you apply it to your garden, the salts get left behind as the water evaporates or gets used by plants.
Over time, heavy or repeated use of Epsom salt can cause unhealthy salt accumulation in the soil. This is especially problematic for plants that are sensitive to high soil salt levels, like beans, carrots, onions and many perennials.
Frequent magnesium sulfate applications can also alter soil chemistry by raising the pH and displacing other minerals, like calcium, that plants need.
To avoid negative impacts, you should limit Epsom salt use, only apply it to magnesium-deficient soils as determined by testing, and flush soils with extra water after application.
3. Magnesium Levels Difficult to Control
One of the main difficulties with using Epsom salt in the garden is controlling the amount of magnesium plants receive.
If soils are truly deficient in magnesium, identifying and correcting that deficiency with supplemental magnesium can be helpful. However, accurately determining how much Epsom salt to apply to meet the exact needs of your soil and plants is not easy.
Application rates on Epsom salt packages are very general. More precision requires thoroughly testing your soil and carefully calculating amendments based on those results. Even then, it is hard to control how rapidly plants absorb the magnesium and how it moves through the soil.
Too much magnesium from Epsom salt can inhibit calcium uptake. Excess magnesium application to soils that are not deficient can hinder plant growth and damage soil structure.
4. Questionable Pest Control
Epsom salt is often said to control pests like slugs in the garden. The logic behind this claim is that the abrasive salt crystals will deter soft-bodied slugs from traversing areas where Epsom salt is spread.
Research has shown, however, that Epsom salt does not provide effective or long-lasting slug control. The slugs are temporarily irritated by the salt but soon recover and return to treated areas. Salt damage to plants is a bigger risk.
For slug control, baits and traps are more effective solutions that pose less risk of unintended plant harm. There are also many organic options for repelling slugs, like diatomaceous earth, crushed eggshells, and coffee grounds.
Are There Any Benefits to Epsom Salt in Gardens?
While Epsom salt is not the magical garden cure-all that some claim, it does offer a few niche benefits when used properly:
- As a supplemental magnesium source for confirmed magnesium-deficient soils
- As an occasional soil flush to prevent salt buildup
- In small doses to help transplant shock
- As a foliar spray to boost magnesium intake through leaves
It may also help produce slightly thicker foliage and greener leaves, but the impacts are generally mild.
Better Alternatives for Garden Success
Instead of reaching for Epsom salt to boost your garden, try these more effective and sustainable options:
- Get a soil test – This is the best way to identify any nutrient deficiencies that should be addressed.
- Add compost – Compost introduces a broad spectrum of nutrients while improving soil structure and drainage.
- Use slow-release fertilizer – Look for organic slow-release products that provide steady nourishment.
- Apply only nutrients needed – Target any amendments to what soils tests indicate is lacking.
- Rotate crops – Varying what gets planted in each spot avoids nutrient depletion.
- Mulch beds – Mulch insulates soil, conserves moisture and replenishes organic matter.
The Bottom Line on Epsom Salt
While Epsom salt might help correct a confirmed magnesium deficiency, research does not support the myriad claims of its benefits for most gardens. Routine Epsom salt use carries risks of unwanted salt buildup, nutrient imbalances, and plant damage.
For prolific gardens and healthy plants, focus instead on building properly amended, well-drained soil with plenty of organic matter. Follow fertilizer guidelines carefully and have soil tested periodically to pinpoint any nutrient shortages. With smart practices, Epsom salt is generally not necessary.
In most cases, Epsom salt does more harm than good. It is best to avoid using it in your garden unless soil tests confirm a need for magnesium. Even then, amendments tailored specifically to soil test results are preferable.
The minimal yields and growth improvements offered by Epsom salt are simply not worth the potential soil damage and poor plant health it can cause through salt buildup and nutrient imbalances.
Frequently Asked Questions
Does Epsom salt keep pests away?
No, Epsom salt does not effectively deter most pests from gardens. It may provide very brief and mild irritation to soft-bodied pests like slugs, but it does not provide lasting pest control. There are far more effective organic pest solutions that do not pose risks to plants.
Should I use Epsom salt every time I plant something?
No, Epsom salt should not be applied routinely when planting. Excessive Epsom salt applications can build up unwanted salts in the soil, cause nutrient imbalances, and even damage plants. It should only be used occasionally and based on soil test recommendations for confirmed magnesium deficiencies.
How much Epsom salt should I use in my garden?
There is no single recommended Epsom salt application rate, as needs vary by the specific soil composition, plants grown, and other factors in each garden. Soil testing is the only accurate way to determine if magnesium levels are deficient and any appropriate Epsom salt application rate. When in doubt, it is better to avoid Epsom salt altogether rather than over-applying it.
When should I apply Epsom salt to plants?
The optimal timing for Epsom salt application depends on the intended purpose:
- To correct magnesium deficiency – Apply early in the growing season before magnesium needs peak.
- As transplant shock relief – Water in a dilute solution at planting time.
- As a foliar spray – Spray leaves 1-2 months after planting or when deficiency symptoms appear.
However, the best approach is to avoid Epsom salt altogether and instead build healthy, balanced soil. Amend and fertilize appropriately based on soil testing results.
What vegetables benefit from Epsom salt?
No vegetables inherently “benefit” from direct applications of Epsom salt. Small doses may help relieve transplant shock or provide supplemental magnesium in confirmed deficient soils. Some plants like tomatoes, peppers, and roses may show mildly enhanced foliage and greener leaves.
However, the risks of soil salt buildup, nutrient imbalances, and potential plant damage outweigh any unproven advantages. For prolific vegetable gardens, balanced soil fertility through compost, organic matter, and targeted fertilization is preferable to Epsom salt applications.
Does Epsom salt keep squirrels out of garden?
No, Epsom salt does not effectively repel squirrels or other wildlife from gardens. While it may initially irritate soft paws, squirrels will quickly ignore and recover from any discomfort. Salt accumulation in soil can also hinder healthy plant growth over time. There are much better humane options for deterring squirrels, like fencing, repellents, and removing food attractants.
Conclusion
Epsom salt is frequently touted as a miracle cure for gardens. However, scientific evidence does not support most of the claimed benefits. Indiscriminate use often does more harm than good by building up soil salts, causing nutrient imbalances, and potentially damaging plants.
The best practices for a thriving garden include building soil organic matter, testing soil periodically, and making amendments only as needed based on results. With a few exceptions like occasional magnesium supplementation in deficient soils, Epsom salt is generally an unnecessary garden additive.
For the healthiest plants and most productive gardens, avoid relying on Epsom salt applications. Instead, focus your efforts on creating balanced, fertile soil through organic practices.