Question: How can I identify iron deficiency in my lawn?
Answer: Iron deficiency is characterized by yellowed leaves with dark green veins. That’s true with grasses, too, although their veins run the length of the leaves, so they’ll actually end up looking striped if iron is lacking. St. Augustine is the only Texas turfgrass that is likely to show true iron deficiency. Other things can cause the grass to turn yellow, but only iron will give the stripes. Sometimes this will show up within a week or two after you have used a high-nitrogen, quick-release plant food such as ammonium sulfate (21-0-0). Go back to your quality, slow-release nitrogen source. St. Augustine is most commonly affected. Bermuda almost never is. Remember, when you apply products with iron to your turfgrass, that granules that land on your drive or walk must be swept away quickly, before they collect moisture and cause rusty stains on your concrete.