Question
Hello Will,

A post elsewhere on this site suggests that magnesium sulfate found in Epsom salts aids flowering plants to bloom. Is there any truth to this and, if so, how to apply? Thanks for your response.

Sabine


Answer
Hi Sabine,

I am not responsible for the posts of other experts on this site. In fact, I frequently disagree with some of the outdated, unprofessional advice that is offered up here. Each expert posts independently.

There is some truth to Epsom salts aiding flower development, but there is much more to it than that. Magnesium is a minor element that must be present in order to make phosphorous available to the plant. Phosphorous is a major element that is important to flower development. So therein lies the truth of the statement that was posted.

However, whether one should use Epsom salts to aid flowers in your potted plants is a different question. Most potting mixes have enough of the very minute quantities of magnesium that plants need. In plant nutrition, adding more than the necessary amount of elements can be toxic. So if you add more of any one element than is desirable, you may create more problems than if you had added none.

Determining the correct proportion of magnesium or any of the other elements is quite difficult, particularly since magnesium is used in such small quantities. Quality commercial fertilizer manufacturers produce complete fertilizers that have all of the major, minor and trace elements in the correct proportions. Although it is theoretically possible for you to this this on their own, it is highly improbable that you will get it right. If you are determined to add Epsom salts to your plants, then use only a very small quantity - maybe a quarter tsp. per pot.

In the old days when chemical analysis of nutrients was not understood and commercial fertilizers not readily available, folks had to rely on what they had around the house. Epsom salts was one of those products and it was helpful especially in areas where soil was deficient in magnesium. I think that is the origin of the advice to use Epsom salts on your flowering plants, but it is outdated.

Finally, I will note that there are other factors in flower development that are far more important than nutrients of any kind. Having adequate light is the most critical factor. Keeping your potted plants quite potbound is another very important factor. Proper watering is essential for any plant. And some flowering plants require dormant or semi-dormant periods or periods of extended darkness to flower. Using fertilizers to promote flowering is often a distraction from these other more important considerations.

I hope I haven't gone on too much here, but your question is a good one and raises a number of important issues that I wanted to address.

If you want more specific information about fertilizing plants, send an email request to my address below and I will send you my article on this topic.

Please let me know if any of this is unclear or if you have any additional questions.

Visit my website at  www.HorticulturalHelp.com

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Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

You can E-mail me directly at: [email protected]