Rose Guide
How to Use Epsom Salt on Roses
Epsom salt (magnesium sulfate) can encourage new basal canes and greener foliage in magnesium-poor soils. Apply about a tablespoon around the base in spring — but only if your soil actually needs magnesium.
Epsom salt supplies magnesium, a nutrient roses use in chlorophyll and cane production. Where soil is genuinely low in magnesium, a spring application of about a tablespoon scratched in around each plant — or dissolved in water — can promote fresh basal breaks and deeper green leaves.
It is not a cure-all. If your soil already has enough magnesium, adding more does nothing and can unbalance other nutrients. A soil test tells you whether it is worth using at all.