If you’ve seen the gorgeous cover of the summer issue of Garden Making, you’ll know why roses are on my mind. I’ve already been out to purchase Epsom salt from the drugstore (and my supermarket carries it, too); now I’ll head into the garden with a measuring cup to deliver treats to these stunningly beautiful plants.
It’s still too early to fertilize roses that haven’t yet sprouted new stems and leaves. Feeding plant nutrients (nitrogen, phosphorus, and potassium) to roses before they have the means to process the foods into carbohydrate energy can burn tender roots and cause shock. But this is an ideal time to provide a dose of Epsom salt to strengthen the shrubs and encourage them to grow more woody canes, which will result in increased flowering potential and better winter hardiness.
Epsom salt is a natural mineral compound containing magnesium and sulfur, two natural elements roses use to trigger new wood (called basal breaks), sprouting low down near the shrub crown. This new wood adds to the structure of the plant, increasing its capacity to carry flowers, and benefiting the health and durability of woody canes.
Before planting a bareroot rose, soak its roots in a bucket of one-half cup of Epsom salt per gallon of water overnight. Use the soaking water to water the shrubs into their holes. When planting a potted rose, work one-quarter cup (60 mL) of Epsom salt into the soil in the planting hole, and scratch another one-quarter cup in the soil over the root zone in midsummer. Established roses should receive one-half cup (125 mL) spread in a circle around the shrub and lightly scratched into the soil over their roots. (For more information about gardening with Epsom salt, see this article from the National Gardening Association: garden.org/articles/articles.php?q=show&id=68&page=1.
And whatever Epsom salt is left over from feeding to roses can, of course, go into your bath water!