When to Apply Iron to Your Lawn

Homeowners choose to plant grass like Bermuda, Fescue, and Kentucky Bluegrass for their deep greens, so a pale or yellowing lawn is never a welcome sight. However, when it’s due to an iron deficiency, it’s usually an easy fix.

If your yard is deficient in iron, or if it isn’t acidic enough, the grass isn’t able to produce chlorophyll. There are both liquid and solid forms of iron that you can use to supplement your yard, and these supplements can also be a great way to encourage the grass to be its greenest.

How Will Iron Green Up My Lawn?

Plants, including grass, use iron to support the chlorophyll production process, and low iron levels in the soil means the grass may not have enough of this mineral nutrient to produce its green color. Grass that is deficient in iron will green right up with an application of a liquid or granular supplement.

If you think your grass may not be getting enough iron, inspect the blades to be sure pests, disease aren’t stressing them, or over (or under) watering, then do a soil test to be sure the lawn isn’t nitrogen deficient.

How Do You Tell Between Iron and Nitrogen Deficiency?

Aside from a soil profile test, you can tell a nitrogen deficiency apart from an iron deficiency by looking closely at the grass blades: a yellowness throughout the leaf, from the bottom up, is a sign of nitrogen deficiency, but an iron deficient blade of grass will be an uneven pale color with some green still in the veins.

Testing For Iron

Luster Leaf 1601 Rapitest Test Kit for Soil pH, Nitrogen, Phosphorous and Potash, 1 Pack

While home soil tests will check for the primary 3 macronutrients (nitrogen [N], phosphorus [P], and potassium [K]), most DIY tests don’t show micronutrient levels. University extension programs can analyze soil samples for micronutrients, but there is another way to do it yourself. If your soil test shows that your yard has normal levels of nitrogen, a pH test will tell you if any potentially present iron is unable to be absorbed due to the low acidity level.

When soil is too alkaline, it limits the availability of iron for grass roots to absorb. Grasses generally like soil to be slightly acidic to neutral pH, around 6.5 to 7. Iron is best absorbed in acidic soils. If there is too much phosphorus, like lime or another fertilizer with high P levels, it can inhibit plants from absorbing the iron, even if the iron levels are adequate.

A soil acidity test will help you know how much correction is needed to lower the pH level from high alkalinity. A sulfur-based fertilizer or an iron sulfate application can help balance the soil acidity and help your plant start absorbing the nutrient again for a healthy green lawn.

How Do I Manage The Iron In My Yard?

There are multiple options when it comes to supplementing your soil to correct for an iron imbalance. Even when iron and acidity levels are good, you may want to give your grass a color boost. To achieve your color needs, there are liquid and granular options made with synthetic or organic formulas:

  • Synthetic – Synthetic iron fertilizers are produced with isolated nutrients that are more immediately available to your grass than organic sources of nutrients. For a quick delivery of iron, a synthetic formula will help your grass green up quickly, but it isn’t a permanent correction for a soil profile low in iron or high in alkalinity.
  • Organic – Organic fertilizer uses iron-rich ingredients to condition the soil and deliver the vitamins to the roots of the grass. This is a longer-term correction, although concentrations will be lower and results may take several weeks to be seen, although the effects will last longer as well.
  • Liquid – Liquid forms of iron supplement are available to plants immediately and don’t need time to break down. These formulas are usually foliar, sprayed across the lawn, and absorbed by the grass Liquid iron will help the grass stay as green as it can be for a few weeks and can then be reapplied.
  • Granular – Solid forms of iron supplement may take a couple of weeks to be used by the grass, since these have to be dissolved slowly and will be absorbed a little bit at a time. This more systemic solution adds iron and other nutrients to the soil for longer-term coverage.

Granular products like Dr. Iron and Ironite contain iron at a ratio of 20% to 22%, whereas liquid products like Southern Ag and LawnStar are in concentrations of 5% to 6%. Since the liquid formulas are absorbed immediately, too high of a concentration can damage the plant with excessive nutrients. However, this also means they can be applied more frequently throughout the year than a solid formula.

When Should Iron Be Applied During The Year?

Monterey LG7115 Dr Soil Acidifier Granules Iron and Elemental Sulfur Acidic Fertilizer, 7 lb

The best time to apply an iron supplement is during the grass’ growing season, although this will also depend on the formula you apply. Ironite, Dr. Iron, and other solid supplements contain a little fertilizer, and when putting them down in the spring, they can be applied with your typical macro fertilizer as well without over-applying any ingredients (double-check your products to be sure!)

Fertilizer-based iron shouldn’t be applied in the middle of summer when the grass will likely be stressed from heat and dryness. The grass may absorb more of the fertilizer than it would when it isn’t stressed and can further strain the lawn by encouraging growth despite stressful conditions. The middle of summer isn’t a period when you want to promote growth in your grass, but if you want it to green up, you can apply an iron supplement that doesn’t contain any fertilizer.

Liquid iron usually doesn’t contain any extra nutrients and can be applied to give your grass a boost of chlorophyll productivity without encouraging extra growth. These products use chelated iron, which means that the mineral molecules have been altered so they will be absorbed quickly through the leaf tissue of the grass.

How Often Can You Apply Iron To Your Lawn?

Ironite 100519460 1-0-1 Mineral Supplement/Fertilizer, 15 lb

You can spray a liquid iron on your lawn with 2 to 3 weeks between applications. The iron is absorbed and used quickly, and the effects will fade after a couple of weeks. This is great for a boost but isn’t a long-term solution to soil that is deficient in the nutrient.

How often to apply Dr. Iron or Ironite will be much lower since these products stray in the ground longer. They also contain an amount of sulfur, which will increase the acidity of the growing environment to make sure the iron will be absorbed. Too far on either side of acidic or alkaline isn’t good for the health of the grass.

Can You Apply Ironite And Fertilizer At The Same Time?

Ironite and other granular iron supplements can be applied with fertilizer during grass’ early growing periods, in early spring, early summer, and early fall. Fertilizer shouldn’t be applied with iron supplements in the middle of summer since they will encourage growth during a mildly stressful period for grass. These solid iron supplements and fertilizers will stay in the soil longer and be available for a few months, so planting early will show results over the upcoming season.