Is Epsom Salt Good or Bad For Roses?

Whether you’re just starting to grow roses or are a seasoned expert, you’ve likely heard the claim that Epsom salt works miracles in the garden. Tutorials on using it for roses abound on Pinterest and YouTube. Many gardeners use it because the tip was passed on by parents or grandparents who swore by its efficacy.

Epsom salt is cheap, widely available, and easy to apply. It’s no wonder that many gardeners use it as a homemade gardening solution. But before you start pouring on the salt, is there truth behind the benefits of Epsom salt for roses?

While websites, friends, and family tout the benefits of Epsom salt as a cure for rose pests and diseases and an essential for big, productive plants, what does the science say? Are these benefits myth or fact? Let’s dive deeper into the use of Epsom salt for growing roses.

A Brief Overview

What is Epsom salt? Epsom salt, usually purchased in bags of dried crystals, is the mineral compound magnesium sulfate, or MgSO₄. It was accidentally discovered in Epsom, England by a cattle farmer over 400 years ago.

Epsom salt became popular for its health uses, namely for easing aching muscles and joints when added to a nice, warm bath. The specific origin of its use in the garden is unknown, but was encouraged and spread by the Epsom Salt Council.

Should you use Epsom salt in your garden? Will it help your roses bloom more? Opinions among gardeners vary, and Epsom salt folklore abounds. Let’s dig into what the research actually says about Epsom salt and roses.

The Long Answer

An internet search on the real role of Epsom salt in growing roses will result in an abundance of articles that contradict each other. Similar to other recommended DIY rose enhancements, most tips based on its benefits are anecdotal, rather than scientifically based.

One test, conducted by the National Gardening Association, asked 6 rose growers to use an Epsom salt foliar spray on one rosebush each and report back. The report doesn’t say how many gardeners noticed better results. However, one of the growers is quoted saying his treated rose was bigger, with better color.

Aside from this very small test, there is little scientific evidence that Epsom salt benefits our roses. Let’s examine common myths surrounding Epsom salts, and let you decide!

Myth or Fact: It Deters Pests

Epsom salt is touted as a weedkiller, a pest killer, and a fertilizer that grows stronger plants. Can it really do all these things? If so, let’s buy stock in the stuff!

The idea that Epsom salt might be effective homemade pest control may go back to a 1930 study. Subsequently refuted, that study said grasshoppers on bean plants were controlled by the compound.

Unfortunately, there is no scientific evidence that common rose pests are deterred by Epsom salt. In fact, more recent studies show no effect of Epsom salt on rose pests like aphids, caterpillars, and slugs.

Sadly for us gardeners, most rose pests have individual life cycles, sensitivities, and habits that require a specific approach. There’s no one size-fits-all pest solution in rose gardening. Most products that say they do it all often do more harm than good. When trying to control pests, you need to identify the pest correctly and treat specifically for that pest to be truly effective.

Myth or Fact: It Creates Stronger, More Productive Roses

The idea that Epsom salt results in bigger, more beautiful roses is a pervasive one. Relying on anecdotal evidence, gardeners apply Epsom salt as a fertilizer to their roses, just like they were told to by a well-meaning gardening friend.

However, there is little evidence to support this claim. No research has proven that Epsom salt is helpful for rose growth or bloom production. In fact, applying Epsom salt when your soil doesn’t need it can upset the balance of nutrients and micronutrients in your soil. This can actually negatively impact your roses.

Roses, like all plants, rely on the essential macronutrients to grow. They rely on nitrogen for strong foliage, phosphorus for flower production, and potassium for strong roots (along with other benefits). When you purchase fertilizer for your roses, you want a balance of these 3 nutrients, ideally in a 10-10-10 ratio.

Micronutrients like magnesium, sulfur, and calcium are also needed, but only in small amounts. Epsom salt is often applied by gardeners who believe they’re giving their roses a boost with additional magnesium.

The truth is, scientific evidence has shown that magnesium is rarely deficient in garden soil. More importantly, adding it can prevent the uptake of other important nutrients, like calcium.

If you already apply a balanced fertilizer or organic compost annually, your soil likely has plenty of the macro and micronutrients present to grow beautiful roses. Overdoing the amount of magnesium via Epsom salt application will only disturb this balance. This could potentially prevent your roses from getting other essential nutrients.

So, how do you know if your soil has adequate magnesium levels? The only way to be sure is to order a soil test. You can often do this for free through your local county extension office, but tests can also be ordered online.

If you have particularly sandy, acidic soil, there’s a chance of magnesium deficiency. However, you shouldn’t assume the risk of applying Epsom salts unless your soil test indicates the need for it.

Myth or Fact: It Prevents and Treats Rose Diseases

Browsing pinterest or instagram, you may come across homemade recipes containing Epsom salt for common rose diseases like Powdery Mildew.

Sadly, these solutions are unlikely to work. The magnesium in Epsom salt has been tested to reveal no effect on powdery mildew or black spot. It can even cause leaf-scorch when applied liberally.

Sulfur, however, can sometimes be an effective disease and pest treatment. However, the levels in Epsom salt lack enough sulfur to have an impact. Gardeners struggling with rose diseases will have more luck using horticultural sulfur and other proven remedies for their specific diseases than Epsom salt.

Myth or Fact: It Treats Yellowing Leaves

No one wants to see yellowing leaves on previously pretty green rose foliage. Before you reach for the Epsom salts, consider the myriad reasons it might be happening.

There are a variety of reasons your rose leaves may be yellowing. Yellow leaves can show up due to nitrogen or iron deficiency, over fertilization, over or underwatering, pests, or disease. You’ll want to correctly identify the problem before treating it with magnesium, which might be ineffective.

When magnesium deficiency is causing yellow leaves, a very specific yellowing pattern will show up. It will first appear on the older leaves of the rose. The veins of the leaf will stay green, while the remainder turns yellow, creating a particular arrow-head shape. This is also called interveinal chlorosis.

In this case only, magnesium delivered via Epsom salt can be a potential foliar treatment. Test your soil to be certain. If a magnesium deficiency shows up, mix a spray of one tablespoon dissolved Epsom salt to one gallon warm water. Mist the leaves, and see if color improves.

Spray in the early morning or evening to allow foliage to dry and prevent scorched leaves as it interacts with the sun.

Myth or Fact: Epsom Salt is Harmful to the Ecosystem

When unnecessary magnesium is applied to plants and soil, it’s not absorbed and must go somewhere. Epsom salt is highly soluble. This means it washes away into our waterways, potentially affecting aquatic life and impacting soil nutrient levels.

In addition, excess magnesium has been linked to reduced root colonization of beneficial microbes, and releases toxic aluminum into soil and water.

Very small amounts in your garden may be okay. But it’s not worth the risks without a soil test indicating a need for magnesium.