Updated: Mar 2, 2020
Epsom salt, magnesium sulfate, is an inexpensive measure to improve your garden. Epsom salt helps germinate seeds, makes plants grow bushier and produce more flowers (by increasing chlorophyll production), and also deters pests. Magnesium allows plants to absorb valuable nutrients from the soil, like nitrogen and phosphorous, which are both very important to plant growth.
Tests done by the National Gardening Association confirms that roses fertilized by epsom salt grow bushier and produce more flowers. It also makes pepper plants grow larger than those only treated with commercial fertilizer.
When to use epsom salt?
Take visual cues from your plants to recognize if the soil is being depleted of certain nutrients. If all the plant's leaves turn yellow, that might be a sign the plant needs more sulfate. If flower leaves turn yellow between the veins (veins stay green), the plant may need more magnesium. Some nutrient disorders display the same way, so if you want to be certain you can test the soil.
Improve seed germination
Add epsom salt to the soil as an amendment before seeding. This mineral will aid in seed germination as well as strengthen the plant's cell walls which means stronger seedlings.
1 cup of epsom salt per 100 sq. feet of tilled soil
Mix 1-2 tablespoons into the soil at the bottom of each hole before dropping the seed in.
Counter transplant shock
Sprinkle epsom salt into the bottom of transplant holes or make an epsom transplant solution.
Remember to add a layer of soil on top of the sprinkled salts so the roots don't come into direct contact with it.
Epsom transplant solution: 1 tablespoon epsom salt to 1 gallon of water. Remember to saturate the transplant hole with regular water before watering with the epsom transplant solution.
Adding epsom salt after plants are transplanted will help injured roots overcome transplant shock.
Prevent leaf curling
Leaf curling may be caused by a magnesium deficiency.
To apply, add epsom salt to the base of the plant.
Faster absorption, Mix 2 tablespoons of epsom salt to 1 gallon of water and apply directly to leaves.
The fruit to plant size ratio on tomato plants is higher than normal, which makes a magnesium deficiency more likely. Tomato vines are prone to calcium deficiency (blossom end rot), thus the majority of tomato fertilizers contain calcium, which will compete with magnesium for root absorption. Due to this fact, foliar application of epsom salt is more efficient.
Water tomato vines with epsom solution, 2 tablespoons to 1 gallon of water, every 2 weeks.
Feed tomatoes epsom salt 2x as often as other plants.
Improve your pepper plants
1 tablespoon of epsom salt for every foot of height around the drip line of the pepper plant, 1x week.
Grow sweeter fruit
Apply to fruit and nut trees, bushes and vines.
Other plant applications
Houseplants: 2 tablespoons per gallon of water; feed plants monthly.
Roses: 1 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 un-planted bushes in 1 cup of Epsom Salt per gallon of water to help roots recover. Add a tablespoon of Epsom Salt to each hole at planting time.
Shrubs (evergreens, azaleas, rhododendron): 1 tablespoon per 9 square feet. Apply over root zone every 2-4 weeks.
Lawns: Apply 3 pounds for every 1,250 square feet with a spreader, or dilute in water and apply with a sprayer.
Trees: Apply 2 tablespoons per 9 square feet. Apply over the root zone 3 times annually.
Garden Startup: Sprinkle 1 cup per 100 square feet. Mix into soil before planting
Routine amendments: Add epsom salts to fertilizer and to soil monthly, or mix 1 tablespoon to 1 gallon of water and spray directly on leaves every 2 weeks.
There are a multitude of recipes for epsom salt applications in the garden, find the ones that best suites your needs. If everything gets too confusing just remember - for maximum benefit apply epsom salts at the time of planting, again at first signs of growth, and when flowers are in full bloom.
It is almost impossible to use too much epsom salts since it has a neutral PH. The crystals break down into water, magnesium and sulfur. Those three chemicals are all beneficial in someway to most plants, unlike commercial chemical fertilizers which stay in the soil.
Epsom salts are recommended by master gardeners and commercial growers.