Epsom salt has a cult-like following among tomato growers, for a good reason.
However, too much of a “good thing” could harm your tomato plants’ health, ultimately causing stunted growth, poor yields, and failing plants.
Like fertilizer, you need to apply epsom salt on a schedule to ensure that your plants are safe, healthy, and happy!
The Ideal Application Schedule for Epsom Salt
The primary time to apply Epsom salt is at planting. Place a single tablespoon in the planting hole, cover it with compost, then plant your tomato and back fill the hole.
You may decide to apply Epsom salt once more through the growing season, to help protect the plants from magnesium deficiency.
If you have a known magnesium deficiency within your soil, you may need more; instead of over-applying, watch your plants for symptoms of magnesium deficiency. The key to healthy, productive plants is listening closely to their needs- whether that be a particular nutrient that isn’t found in abundance, or help with controlling pests. We’ll list the symptoms further along in this post.
The Epsom Salt Myth: Does Epsom Salt Prevent Blossom End Rot?
Many, many gardeners swear by Epsom salt as a cure-all for blossom end rot. However, these gardeners are mistaken.
Epsom salt does not protect plants from blossom end rot in any way; it actually provides additional magnesium. A lack of magnesium can result in problems with plant growth and fruit production. If you have poor soil, it’s possible to have multiple deficiencies; the increased amount of watering following the application of Epsom salt may lead to this belief as well, as BER is directly related to watering; if BER occurs, more frequent watering will solve the problem in most cases.
Therefore, while these salts can definitely benefit your plants, you should not consider them to be a remedy for blossom end rot in tomatoes (or peppers, or melons…)
How to Recognize the Signs of Magnesium Deficiency in Tomato Plants
Magnesium deficiency in tomato plants is commonly identified by a form of chlorosis, called interveinal chlorosis.
This means that you will see a loss of healthy, green coloration between the veins of the tomato plant’s leaves. Rather than being focused in particular spots (like fungal infections or pest damage), the spots will be dispersed among the leaves. The older leaves will be the first ones affected, as the plant will move magnesium from the older leaves to the newer, younger leaves.
If you apply a treatment of epsom solution to the plants, you’ll see that newer growth will appear without discoloration, resulting in healthier green leaves being produced. You’ll also see that green, older leaves do not undergo chlorosis. You cannot repair older leaves that exhibit magnesium deficiency induced chlorosis, but your plants will quickly produce more foliage.