Too Much Iron in Your Lawn (How to Tell + Fix)

Too much iron on your lawn could come from a spill or accidental over-application. Either way, the signs of too much iron in your lawn are often easy to spot and the condition is typically diagnosed with just one test. Below you can learn how to figure out if your lawn has an iron problem and what the most effective treatment method is.

What Happens When You Have Too Much Iron in Your Lawn?

Too much iron in your lawn often causes the grass to turn so dark green that it’s almost black due to an interruption in the chlorophyll production and storage process. If this condition persists for too long, the lawn will begin to die. Heavy iron concentrations cause the most damage in hot weather and even if your lawn’s iron levels are high in the Spring, you may not see many signs until the beginning of summer.

Signs That Your Lawn Has Too Much Iron

Applying more iron than necessary to your lawn can have unpredictable results. Below are a few of the things that could be happening if your lawn’s iron levels are too high. However, be sure you rule out any other cause of the same symptom before deciding that the cause of this undesirable outcome is iron as most other causes are much more harmful than high iron levels.

Dark Green to Black Lawn or Patches of Lawn

Iron is typically added to a lawn to help the grass out-compete weeds. Iron can also kill moss and molds virtually on contact. When it kills moss, the iron interrupts the ability of the moss to control chlorophyll production.

In sufficient quantity, the same thing can happen to your lawn. This means that the grass will temporarily turn dark green or even black or purple due to the amount of chlorophyll stored in the blades of grass. In most situations, this color will begin to fade in 3 to 4 days and the grass will resume its usual appearance, as long as the soil’s pH is still within an acceptable range.

Your Soil pH is Low

Low soil pH can result in your grass turning brown and a bit sludgy or wet in appearance within weeks. Too much iron, especially from a recent application of an iron product, can result in the pH of your lawn dropping as many as 3 points (from 7.5 to 4.5, for example) almost immediately. A low pH also compounds the problem of high iron as if the pH of your soil is too low, the grass will have an even harder time absorbing and getting rid of the excess iron.

The Tips of Your Grass are Light Brown or White

While not a common presentation compared to the above options, the lightening of the lawn can happen under specific circumstances. Too much iron in your lawn can cause the ends of your blades of grass to “burn” or dry out suddenly, especially in hot weather (above 80F) and during periods of heavy summer rain. It may be counter-intuitive, but adding more water in high iron conditions, including rain, can result in grass that appears scorched and brittle.

How to Confirm That Your Lawn’s Iron Level Is Too High

There are two ways to test your lawn and determine, with a high degree of certainty, if your lawn is suffering from high iron. First, you want to do a soil pH test. Chemical test kits and strips are often more accurate than less expensive probe-based meters. If you do use a probe-based meter, damp soil will often produce more accurate results. Whichever test you choose, if the pH is less than 5.5, your lawn probably has high iron as few other conditions can cause a pH drop this severe.

If the pH of your soil is above 5.5 but below 7 (or the ideal pH of your particular grass type), you may have high iron and it can be beneficial to correct this pH problem but the problem may also correct itself over time. A pH in this range does not immediately suggest a high iron problem.

If you still suspect high iron or your lawn is showing signs like those described above, contacting your local agriculture extension office could connect you with a lab that would be willing to conduct a more in-depth soil content test or foliar test. These tests, however, can be expensive and the collection process and delivery of the samples can take quite a bit of time and care.

How To Lower Your Lawn’s Iron Levels

When your lawn has been given too much iron, it can be difficult to lower these iron levels directly. What you can do is add one or two substances that can support the health of your grass and soil while the iron is dealt with naturally. Below are the best 3 options for soil amendments while your grass is recovering from an overdose of iron.

Treat the Lawn by Adding Lime to Even Out Iron Levels

Adding lime to your soil can help solve the acidity problem that the iron has introduced. Try to add lime if your pH has fallen below 6 and attempt to get your lawn’s pH back up to 6 or a little above. This can make it so that your lawn can absorb the excess iron and eventually use it up. When adding lime, always follow the manufacturer’s directions. Adding too much lime to your lawn, even to course-correct an iron problem, can be fatal for your lawn.

Treat the Lawn by Adding Bicarbonates to Even Out Iron Levels

Adding a specialty bicarbonate product specifically designed for lawn use is less ideal than lime but can save your lawn in an emergency (such as an iron solution spill). The bicarbonate should be added according to the directions on the packaging for specialty products. The use of household baking soda is discouraged as it may further damage or stress your lawn.

Treat the Lawn by Adding Zinc to Lower Iron Levels

One of the best things to do, after adding lime to solve the pH issue, is to add some zinc to your lawn. Always follow the recommended dosage instructions on the packaging of any zinc lawn product and do not increase the dosage just because you are using it to treat the iron.

Zinc will interrupt the uptake of iron by the grass, though the iron will interrupt the uptake of the zinc, too. Overall, this means that your lawn will uptake these substances slowly or they will have a chance to be washed away by water and rain without being absorbed at all.

Improve Drainage to Lower Your Lawn’s Iron Levels

Any standing water will increase the damage the iron can do to your lawn. If there are any wet spots on your lawn, work to improve the drainage in these areas to prevent permanent damage and decrease the local concentration of iron.

How to Adjust the Levels of Iron in Your Lawn in the Future

If you happen to over-correct the iron levels or if you ever intend to add more iron to your lawn in the future, choosing a chelated iron product is recommended. Chelated iron has a much higher safe range for application and is far less likely to cause iron levels that are too high, even if you accidentally add a bit more than the safe range calls for. While ferrous sulfate may be the old gold standard due to price and availability, chelated products are now widely available and the cost difference should be very small.