Iron Sulfate for Plants: What It Is And How to Use It

All plants do not have the same type of requirements and, when we talk about soil pH, we are dealing with one of the most difficult problems to solve or one that causes the most discomfort, especially for less experienced gardeners. Learn all about iron sulfate for plants in this article.

Iron sulfate is one of the most commonly used products in this type of situation, although to get the most out of it, it is necessary to know it well. If you want to learn what is iron sulfate for plants and how to use it, or even how to make homemade iron sulfate for plants, join us in this article.

What Is Iron Sulfate

When we talk about iron sulfate for gardening we are always referring to iron (II) sulfate, a chemical compound obtained by reacting sulfuric acid with metallic iron.

It is very easy to find in gardening stores and other specialized surfaces, usually in two large formats: as a powder, bluish-green in color, or the form of white or brown granules. The powder is more rapidly absorbed, while the granules act much more gradually.

What Is Iron Sulfate Used for Plants?

The main use of this substance in gardening is to lower the pH of the soil. Plants need to absorb a multitude of nutrients from the soil, but when the soil is too alkaline, the roots can no longer get the iron they need and symptoms of iron chlorosis appear. When the leaves of the plant seem to lose color and only the nerves look green, it is a clear sign of chlorosis, and it usually does not mean that the substrate or soil does not have iron, but that the roots of the plant cannot absorb it because the pH is too high.

This happens especially often with plants such as hydrangeas, camellias, gardenias, or azaleas, among many others. These are acidophilic plant species, which need acidic soils to develop well, i.e. low pH. Hydrangeas deserve a special mention here, as they are often forced to produce pink flowers by inducing chlorosis, a practice that stresses and seriously threatens the health of the plant. If you are going to get a hydrangea with pink flowers, make sure they are pink by variety, and that their leaves are a healthy green and not yellow or white.

It is also common to find plants suffering from iron chlorosis in areas where tap water has a lot of lime in it. Watering plants with tap water is a very common practice, and there is nothing wrong with it when we are not dealing with acidophilic species. However, when the water is heavily laden with lime, continuous watering ends up altering the pH of the soil in depth, raising it and making it alkaline. If you start using iron sulfate for your plants because they need it, be sure to start watering with neutral water, or let it stand for 24 hours before using it, and do not use the last few inches of the container.

To learn more about the subject, we recommend you to read about How to measure soil pH. We also advise you to learn more about this problem by reading this other post about Chlorosis in plants: what it is and how to eliminate it.

homemade iron sulfate for plants

How To Make Homemade Iron Sulfate

It is possible to prepare homemade iron sulfate, although we recommend doing so only in extreme cases in which you cannot get it on specialized surfaces. The reasons are that the prepared iron sulfate is not expensive, and with the one, we will make at home there is no way to calculate exact doses, besides being a tedious and slow process. Even so, we show you how to do it:

  1. Prepare a container with water, which can be simply a plastic bottle.
  2. Add some iron materials such as nails or nuts, submerged in water along with a small amount of sulfur.
  3. It is important to stir it two or three times a day so that the sulfur reacts with the iron.
  4. After about 15 days, it will have taken on the characteristic color of iron oxide, and the mixture will be ready to be used in small quantities in the irrigation water and applied if necessary.

Where to Buy Iron Sulfate for Plants?

If you want to buy iron sulfate for plants and do not know where to get a quality one here are the best.

How To Use Iron Sulfate for Plants

It is most commonly applied diluted in the irrigation water or added to the soil of plants in the garden. In pots, it is more common to simply change the substrate for a specific one for acidophilic plants, which already have a suitable pH.

In irrigation water, the proportion tends to be 0.8 tsp (3 grams) per liter, while in the soil it is usual to use about 10 tsp 40 grams per square meter. The application will not work in both cases if we do not stop watering with running water or if we do not rest it beforehand. Even so, it is important to read the specifications and specific indications of each product and make sure to follow them. If iron chlorosis is not stopped quickly, the health of the plant will get worse and worse until it ends up having fatal results, so you must always act quickly.

yellow leave plant iron
About Henry Morgan

We are the Morgan family, Henry, and Morgan, both agronomists from the University of Michigan, where we met. We are experts in putting our hands in the soil and developing organic foods and improving production processes for decades. Likewise, we have worked for companies such as Mondelez International, BASF, Monsanto, etc. currently in our role as science writers for as well as advisors in promoting large scale food growing in urbanized areas. In this website, we share what we are most passionate about, gardening and farming. Enjoy and see real photos on our website.