What is Epsom salt used for plants? How (timing, quantity) should we use it?

Asked October 31, 2020, 11:33 PM EDT

What is Epsom salt used for plants? How (timing, quantity) should we use it?

Montgomery County Maryland

1 Response

Epsom Salt is magnesium sulfate, which can be useful if there is a magnesium deficiency in the soil as indicated by a laboratory soil test. Otherwise, it is not proven to be a beneficial general additive and, like any other nutrient supplement, can lead to harmful excess levels in soils if over-applied (or used in the absence of a deficiency).

Fertilizer recommendations depend greatly on the plants in question, the soil analysis and soil type, time of year, and how the plant is being grown (in containers, in the ground, etc.). If you are curious about the nutrient composition of your soil (in-ground; tests are not intended for potting soil), here is our page with information on soil testing which contains a link to area labs providing the service: https://extension.umd.edu/hgic/topics/soil-testing

For in-ground outdoor trees, shrubs, and many perennials, regular fertilization is usually not needed, recommended, or even measurably beneficial. For houseplants, edible crops, potted hardy plants, and annuals, fertilizer use can be more routine, but specific recommendations will depend on the conditions mentioned above.