What is Ironite and Should I Use it on My Lawn?

You’ve seen the promise — apply Ironite on your lawn and you’ll green it up instantly without that pesky risk of nitrogen burn. But what is Ironite? Does it really green up your lawn? What is iron deficiency and is Ironite the best way to treat it?

Ironite is a brand-name iron amendment for lawns sold by Pennington. Iron amendments treat interveinal chlorosis caused by a lack of soluble iron in the soil. Before using iron amendments, do a soil test, as iron deficiency is more often caused by alkaline soil, compaction, and excess phosphorus.

Does my lawn need Ironite?

Ironite is marketed as a “safe” way to green up your lawn without risking nitrogen burn, but before you add any amendment, get a soil test done! Even when your grass has all the symptoms of iron deficiency, it’s more likely caused by other underlying issues.


What is iron deficiency?

Iron aids a lot of vital functions, including enzyme and chlorophyll production, nitrogen fixing, and metabolism. The primary sign of iron deficiency is leaf chlorosis, where the leaves turn yellow but the veins stay green. It looks kind of like nitrogen deficiency except for those green veins. It starts with recent growth before reaching the older leaves.

But hold up! Just because a plant has interveinal chlorosis doesn’t mean that there’s not enough iron in the soil. Any metallic element deficiency or excess phosphate can cause interveinal chlorosis. And even when plants are deficient in iron, it’s not necessarily that there’s not enough iron in the soil. A soil test will tell you what the underlying problem is and isn’t.

What causes iron deficiency?

Alkaline soil (the pH is too high)

Plants absorb more or less of a nutrient depending on the pH range. Some nutrients, like magnesium, calcium and potassium, are absorbed at alkaline ranges. Other nutrients, like iron and other metallic elements, are better absorbed at acid ranges. If your soil is too alkaline for your grass species, then it’s going to have trouble absorbing the iron that’s already in the soil.

Certain activities, like pouring new concrete, can change the pH level of your lawn, so even if you think your soil is more acidic, it pays to double check.

Compaction, puddling, or heavy clay soil (restricted air flow in soil)

Cool soil and not enough air flow in the soil aggravate interveinal chlorosis. If the soil is compacted, saturated with water, or clay-based, plants won’t be able to access soluble iron.

Insoluble iron (plants can’t absorb this type of iron)

Your soil may have an abundant amount of iron, but it’s trapped in an insoluble form that plants can’t use, like iron oxide. When it’s insoluble, iron just sits there. (This is why not any old iron supplement will help.) When chelates attach to iron, becoming chelated iron, plants can absorb it even in alkaline ranges.

Excess phosphate (too much phosphate)

Like nitrogen, you can definitely have too much of a good thing. Your lawn needs some phosphate, but if you’ve been going hard core with the fertilizer or the amendments, you’re in for some colossal problems.

Phosphorus not only makes it so that plants can’t absorb as much iron, but it combines with iron to become an insoluble iron phosphate that just sits there uselessly.

Too much phosphorus also messes with the mycorrhizal relationship between fungi and plant roots, so can wreak havoc on the healthy soil you’re trying to encourage.

While excess phosphorus can run off, causing environmental problems, phosphorus tends to just sit there in the soil. So even if you’re only applying a bit more phosphorus than needed each growing season, it’ll grow into a bigger problem.

iron deficient lawn

How do I know if my lawn is iron deficient?

To figure out if your lawn is iron deficient, take these three steps:

1 – Inspect the affected grass for interveinal chlorosis

The classic sign of iron deficiency is interveinal chlorosis, where the veins are still dark green but the rest of the leaf has turned pale yellow.

Nitrogen deficiency also shows up as chlorosis, but in this case the whole leaf, veins and all, will turn yellow. It also affects older leaves before younger leaves, while interveinal chlorosis affects younger leaves first.

2 – Send in a soil sample

An iron deficiency in your grass does not always equate a lack of iron in your soil. Throwing on iron chelate is just like putting a bandage over a splinter. Sure, your grass will be a bit healthier in the short run, but it’ll be less healthy and much more work for you in the long run if you don’t diagnose the underlying issue. The soil sample will help you do that.

A soil sample report will tell you the soil pH along with a breakdown of nutrient concentrations, as well as recommendations for fixing deficiencies. You can also take the report to your local extension office for personalized advice from people who are experts in growing in your area.

3 – Apply an iron foliar fertilizer to a patch of affected grass (optional)

Iron chelate foliar fertilizers won’t fix your problem, but while you’re waiting for the soil sample to come back, you can test whether iron deficiency caused the interveinal chlorosis.

Foliar fertilizers are fertilizers sprayed on the leaves to be absorbed directly through the leaves. The downside is that iron becomes immobile once they enter a cell, meaning it doesn’t get passed on throughout the plant where it’s also needed. It is not a long-term solution, or even a short-term one.

It is, however, an effective way to test whether the cause is iron deficiency. Spray a small section of grass with the iron chelate. Wait a couple of days. If iron deficiency was the problem, the grass will green up.

Even if this works, wait for the soil test report before addressing any issues.

How do I fix iron deficiency in my lawn?

You’ve got the soil sample test back, and you’ve tried the foliar fertilizer. Fixing the iron deficiency in your lawn depends on the cause.

Too alkaline soil

If alkaline soil is inhibiting iron absorption, then you can take one of three actions:

  1. Overseed with an alkaline-loving grass. If your soil is naturally alkaline, why fight it? Wheatgrass and clover varieties do well in alkaline soil, and ryegrass (both annual and perennial) do moderately well. Grasses that do well in alkaline soil are more efficient in their mineral absorption, meaning they need less minerals.
  2. Change the pH level of your soil. This option is best taken if your soil’s pH level isn’t naturally alkaline, but changed because of things like pouring cement nearby. Changing the pH level is really tricky, as it’s all too easy to make it too acidic instead. You definitely need to do a soil test with an exact pH before attempting this.
  3. Apply a new layer of topsoil. If you live in a new development or your soil has been eroded to expose limestone beneath, your lawn lacks the depth of topsoil to grow a healthy lawn, regardless of deficiency problems. Regrading with topsoil (with a layer of compost on top) will do your lawn all kinds of good.

Compaction or heavy clay

If compaction caused the iron deficiency, then the quickest option is to core aerate your lawn to relieve the compaction and give your lawn space to breathe.

If the soil test comes back with not enough organic matter (a lawn needs around 3% organic matter), topdress your lawn with a ¼-inch of compost once a year. This will help build nice loamy soil, improve drainage, and relieve compaction over time.

Excess phosphate

Excess phosphorus has one cause: too much fertilizer, especially inorganic/synthetic fertilizers, although compost can also be too high in phosphorus. If your soil test comes back with high levels of phosphorus:

Stop applying phosphorus fertilizers. Adding more fertilizer will just make the problem worse. If you’re using homemade compost, get a soil test done on the compost to check the levels. If you use synthetic fertilizers, consider switching to a natural lawn as there are tons of benefits to you, your lawn, and the environment.

Do not apply Ironite or other iron soil amendments. When phosphorus levels are high, iron and zinc is quickly converted to non-available forms, meaning you might be adding a ton of iron to the soil but the plants can’t use it. In the short term, use foliar fertilizers to treat iron deficiency while waiting for the phosphorus levels to decrease.

Wait until the phosphorus levels decrease to acceptable levels. There’s no way for you to actively reduce the amount of phosphorus in the soil. You just have to wait. How long depends on the conditions and how much phosphorus is in the soil.

In the meantime, now is a great time to consider switching over to a natural lawn, if you haven’t already, or overseeding with more tolerant and hardy grasses that don’t need so much fertilizer. Let nitrogen-fixing clover and other “weeds” grow throughout your lawn to keep up nitrogen levels the natural way.

Low iron or insoluble iron

Your soil test came back with a deficient amount of soluble iron in the soil. Provided you don’t also have the above problems, the best way to treat this is by applying organic matter, whether compost or amendments. Organic matter will put iron and chelates (the thing that iron needs to be soluble) into the soil.

The best natural iron amendments include: manure (especially chicken manure), green compost, greensand, dried blood (from a reputable source!), and seaweed.

If you buy an iron supplement, make sure that it’s iron chelate and not other types of less soluble iron or it won’t be absorbed. Avoid fertilizer combos. If you don’t have a problem with excess phosphorus, you don’t want to create one.

The Risks of Using Ironite On Your Lawn

In the early 2000s, the EPA ran tests on the Ironite brand (when Ironite was owned by Ironite) and discovered high amounts of arsenic and lead. This original formulation came from recycled mine tailings which contained heavy metals like lead and arsenic.

After that finding, Central Garden & Pet Company bought the Ironite brand through Pennington. The EPA had bought and closed the mine that provided the recycled tailing. Pennington reformulated the product. It’s not the same brand that it was.

Still, when the Washington State Department of Agriculture ran tests on the Ironite products, they found amounts of arsenic, lead, and cadmium [PDF], especially in the Ironite Plus (the one that comes with synthetic fertilizer). It’s just at levels deemed safe at a federal level.

Once heavy metals are in your soil, they’re there for good. They don’t break down.

Also, Ironite is not your best source of iron. They use iron sucrate and iron oxide, which are less soluble than chelated iron, especially at higher pH levels.

The Verdict

Instead of reaching for the Ironite, check your soil for high pH, iron levels, and phosphate levels with a soil test and inspect your lawn for compaction or high clay levels. Once you’ve determined the cause, you can treat it much more effectively than simply applying iron amendments — the cost of which can add up really quickly with little effect.

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