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Learn Your Lawn: Chlorosis in St. Augustinegrass

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What Is Chlorosis St. Augustinegrass?


Chlorosis refers to the yellowing or pale appearance of the grass blades due to a deficiency of chlorophyll, the pigment responsible for the green color. It is a common problem that affects many types of turfgrass, including lawns, golf courses, and athletic fields. Chlorosis can be caused by several factors, including:

  • Chlorosis often occurs due to a lack of essential nutrients, particularly iron. Iron is necessary for chlorophyll synthesis.

  • Turfgrass thrives in slightly acidic to neutral soil conditions. When the soil pH becomes too alkaline or acidic, it can lead to nutrient imbalances and subsequent chlorosis. For instance, alkaline soils can cause iron to become less available to the plants, leading to iron chlorosis.

  • Excessive water or poor drainage can result in waterlogged soil conditions, depriving the grass roots of oxygen. This can disrupt nutrient uptake and lead to chlorosis.

  • Compacted soil prevents air circulation and inhibits root development. Inadequate root growth can impair nutrient absorption and contribute to chlorosis.

  • Environmental factors such as excessive heat, drought, cold temperatures, or excessive shade can stress the turfgrass, affecting its ability to produce chlorophyll and leading to chlorosis.

The tricky thing about iron chlorosis in the lawn is that it mimics the symptoms of other lawn ailments. If the uppermost leaves turn pale green or yellowish-green, it’s likely iron chlorosis. It’s also likely that the grass blade’s vertical veins may appear a darker green than the surrounding leaf tissue.


How Can I Prevent Chlorosis In My Lawn?


St. Augustinegrass is very sensitive to iron deficiency and often develops chlorotic symptoms in alkaline (pH > 7.5) soils or iron-deficient soils. If desired, this can be corrected with foliar applications of iron sulfate or iron chelate. Soil applications of a granular iron amendment are less effective in alkaline soils, as the iron may become quickly bound up and unavailable for plant uptake. The application of high-quality compost materials may also be beneficial in introducing micronutrients to your turfgrass system.


A thick, healthy, well-maintained lawn is the best line of defense. Here’s how you can adjust your beneficial cultural practices to reduce the likelihood of Chlorosis:

  • Watering: Excessive watering can intensify the problem, so you should stick to your regular regimen of watering your lawn a few times per week for 30-45 minutes in each area. During hot and dry periods, most lawns should be watered as much as required to maintain its desired green color. Always water in the early morning so the turf has time to dry by nightfall.

  • Mowing: Maintain a regular mowing schedule throughout the growing season. In general, you should keep your lawn between 2 ½ and 3 ½ inches high, but during the hottest weeks of summer, you may allow the grass to grow as high as 4 inches. Never remove more than ⅓ of the grass blade at each mowing.

  • Fertilize Regularly: Regular applications of Weed Man’s specially formulated, slow-release granular fertilizer will help provide your lawn with adequate nutrients. These applications are timed specifically to avoid over fertilizing the lawn.

  • Core Aeration: Aerating your lawn can improve soil drainage and help reduce the likelihood of lawn diseases. This will also alleviate soil compaction and allow water and nutrients to penetrate deeper into the soil.

Your local Weed Man professional may be able to offer other solutions and recommend the best form of treatment that is available to improve the conditions of your lawn.