The origin of these “research based” recommendations is unclear. It helps plants grow bushier. Here are some specific ways it helps with plants: Improves flower blooming. Mix the Epsom salt … Mix into In the soil-Prepare the soil with Epsom salt before planting roses. Epsom Salt per gallon of water to help roots recover. Add a tablespoon of Epsom Salt to each hole at planting time.” There is no published, scientific research on Epsom salts effects upon roses. You need to add a cup of Epsom salt for every 100 square feet of soil. Benefits of Using Epsom Salt on Roses The benefits of Epsom Salt on plants are many including that it’s organic, it’s gentle on plants and it’s cheap! Epsom Salt For Roses. They get a nice new layer of compost on the soil as mulch each spring and fall. It enhances a plant’s green color. You can also use Epsom salt whenever you see your rose bushes getting weaker. Epsom Salt for Tomatoes & Roses. Roses are no exception. I feed my roses with a nice top-dressing of homemade compost! It’ll make them lush and improve flower production. Do not use epsom salt to fertilizer roses in your garden. INSTRUCTION: “Garden Startup: Sprinkle 1 cup per 100 square feet. Epsom salt, a natural mineral, contains magnesium and sulfur.