When to Apply Iron to Your Lawn for Best Results

Iron application can help make your lawn greener and healthier. If you’ve noticed that your lawn’s color is a lighter green or even bordering on yellow, it’s possible that your soil has an iron deficiency. Properly adding iron to your lawn requires careful application and timing. Knowing when to apply iron to lawn areas will get you the best results to keep a green lawn all summer. That said, applying Iron at the wrong time can do more harm than good.

Today I’ll explain what you need to know about the timing of Iron applications to your yard to get that rich, deep green color you want for your grass.

Let’s get started with some basics.

Why is Iron Important for Your Lawn?

Iron supplements for lawns became especially popular with homeowners trying to rival the lovely green grass of golf courses.

It’s especially effective when you apply iron to Kentucky Bluegrass or Fescue Grass lawns. It can help these types of grasses retain a dark green shade during the hottest parts of the summer.

Iron also doesn’t cause extra growth or create a need for additional irrigation, which nitrogen fertilizers do. If you’d like to learn more about the difference between Nitrogen and Iron applications, start here.

When Should You Apply Iron Supplements to Your Lawn?

The general rule is that you should use iron supplements on your lawn in the spring. Of course you can apply iron supplements at almost any time of year, but iron will deliver the best results when applied to your lawn when air temperatures are between 40 and 80 degrees Fahrenheit. The ideal air temperature is in the 60s or 70s. This is why Iron application during the heat of summer may not be as effective or deliver the desired results — it’s too warm out.

Always remember to read the instructions to make sure you are using the supplement properly. Remember that you want to avoid overdoing your lawn with iron.

Apply Iron Only As Needed

Grass usually doesn’t need a large amount of iron. In fact, it’s usually only beneficial to apply extra iron if you have a soil test indicating iron deficiency.

Don’t automatically assume an iron deficiency is the cause of your lawn yellowing or being light in color.

First, ensure that it’s sufficiently watered and has all other major nutrients. If those don’t work, you can consider using iron supplements, but your best way to know for sure what your lawn is lacking and how to improve performance is to perform a soil test. This is the one I use. I order it from Amazon every spring and let those results guide me in applying the right products (and not wasting money on things my lawn doesn’t need) each year.

And if you’re interested in taking the guesswork out of what to do next after you get your soil test results, consider Sunday’s subscription lawn-care plan. They test your soil for you and use local weather data to send you exactly what your lawn needs, when it needs it. It’s pretty fool-proof – you can Click Here for Your Instant Lawn Analysis and take 15% off your order with promo code LAWNCHICK2024.

Two Kinds of Iron Supplements for Your Lawn

Iron fertilizers are found in multiple varieites, but they can be grouped into two main categories:

• Organic Iron Fertilizers
• Synthetic Iron Fertilizers

Organic Iron Fertilizer Products

Organic iron fertilizer is comprised of organic iron sources, such as those found in Greensand and Milorganite. These break down more slowly but are healthier for your lawn in the long term. The iron in them also has natural chelation, which makes it easier for your grass to absorb.

With organic iron fertilizer, you won’t have to worry about your concrete getting stained either. Also, these organic fertilizer products with Iron tend to contain other ingredients that help make your lawn healthier.

Synthetic Iron Fertilizer Products

Synthetic iron fertilizers tend to be inexpensive and act quickly to improve your lawn. Sometimes these will need to be sprayed on your lawn, but many of these products are available in granule form.

If you go overboard with synthetic fertilizer products with Iron you could end up with grass that turns gray (yes, really). Also, synthetic iron fertilizers can leave stains on concrete.

Be careful while applying this kind of product so you do not over-apply or spill it on your concrete driveway or walkways.

Two Forms of Iron Supplement for Your Lawn

Iron supplements for your lawn generally come in two different forms:

• Spray / Liquid
• Granular

Iron in Spray Form

Using liquid iron in a spray form facilitates foliar feeding. This kind of feeding tends to have a more efficient and expedient effect on your lawn (you’ll see results quickly).

You can put the iron directly on the blades of your grass. This means that it will get into the plant’s system more quickly. This kind of treatment will last between 3 and 4 weeks.

Products like spray-on Ironite and LawnStar Chelated Liquid Iron (the liquid Iron product I use, here’s the Amazon link) act quickly and can be useful to improve your lawn’s health and appearance.

Remember to be moderate in how you apply this. If you put on too much, you may end up with a gray lawn instead of the deep green color you’re after.

Iron in Granular Form

Apply granular iron supplements directly on the lawn soil with a broadcast fertilizer spreader or drop spreader. This type of iron supplement for lawns will take longer to have an effect since the structure of its molecules needs to be broken down, which happens over time.

You won’t have to use this kind of iron supplement as often as you would a spray form, though, and the effect on the color of your grass tends to be more enduring.

What to Watch Out For When Applying Iron

It’s important to be aware that iron can stain concrete, and therefore you should be careful to avoid walkways, athletic courts, and concrete driveways when applying iron to your lawn.

This happens because of the chemicals in some synthetic iron supplements.

Iron can leave ugly orange stains (think rust stains) on your concrete patios and other hardscape features of your landscape, so this is something that you will want to keep in mind.

I use a supplement called Dr. Iron (Amazon link) which delivers great results and does not stain concrete, and I highly recommend it, especially if you’re concerned about preserving the beauty of your hardscape features. It works wonderfully to green up my lawn.

Avoid Summer Application to Stretch Your Dollar

Iron may be useful in making your lawn a deeper green color so it really pops in your neighborhood.

And while it’s tempting to throw down Iron supplements early and often, you should apply it when air temperatures are below 80 degrees Fahrenheit to get the best results. Apply in the heat of summer and your supplement will be less effective since your grass won’t be able to absorb it quite as effectively.

Whenever you choose to apply Iron, it’s important to read and follow the manufacturer’s recommendation about coverage and application rate. Use one of these online tools to measure your lawn size to get your application just right.

Additional Resources

• Iron for Kentucky Turfgrasses by Travis Shaddox and Gregg Munshaw, Plant and Soil Sciences at the University of Kentucky College of Agriculture, Food and Environment (https://www2.ca.uky.edu/agcomm/pubs/AGR/AGR246/AGR246.pdf)
• Understanding and Applying Chelated Fertilizers Effectively based on Soil pH by Guodong Liu, Edward Hanlon, and Yuncong Li, University of Florida IFAS Extension (https://edis.ifas.ufl.edu/publication/HS1208)