How to Care for Anemic St. Augustine Grass

St. Augustine grass develops an "anemic" look when the grass plants do not absorb enough iron from the soil to sustain their natural green color. An iron deficiency in the soil causes the leaf blades to turn yellow or white. In severe cases, the grass blades remain small and the edges of the leaves burn. A prolonged deficiency weakens and eventually kills the grass plants, according to the Utah State University Extension. Proper care of anemic St. Augustine grass requires iron supplements and the best cultural practices.

Things You'll Need

• Soil test sample
• Iron chelate
• Hose
• Mower

Instructions

1. Check grass blades for iron deficiency symptoms to rule out a nitrogen deficiency or Saint Augustine Decline (SAD). Iron deficient grass turns yellow from the top of the leaf blade to the bottom. The veins along the leaf blade stay green. Nitrogen deficient grass turns yellow from the bottom of the leaf blade to the top. SAD causes stippling or mottling of the leaf blade.

2. Submit a soil sample to your local extension office for testing. Soils with high concentrations of copper, lime, phosphorus and salt can tie up iron and make it less available to the grass plant. For a nominal fee, most extension offices will test the sample for deficiencies, so that you can correct problems.

3. Apply iron chelate to the lawn in spring. Chelated iron agents are available in granular, liquid and powder form and designated as EDDHMA, EDDHA, HEDTA, DTPA and EDTA. Alkaline soils respond best to EDDHA and EDDHMA chelates; slightly acidic soils respond to EDTA, DTPA and HEDTA chelates, according to the Texas A&M AgriLife Extension.

4. Provide St. Augustine grass with 1 inch of water per week, adjusting for rainfall. Water the lawn thoroughly to prevent drought stress while the grass is still actively growing in spring and to minimize dehydration when the grass goes dormant in summer.

5. Maintain the recommended mowing height of 1 ½ to 2 ½ inches. Avoid cutting more than 1/3 of the leaf blade off. Scalping the lawn initiates iron deficiency symptoms, as the grass struggles to grow back after severe cutting.

Tips & Warnings

• Over-watering a lawn reduces the grass' ability to take up iron.

• Do not apply nitrogen fertilizer to an iron deficient lawn. The fertilizer encourages growth at a time when the lawn cannot absorb enough iron from the soil and makes the problem worse.

References

• Utah State University Extension: Iron Out Plant Anemia
• Texas A&M AgriLife Extension Service: St. Augustine Grass
• University of Arizona Cooperative Extension: Turf Tips: Iron: Some Rusty Facts
• North Carolina State University Cooperative Extension Service: St. Augustinegrass Lawn Maintenance Calendar
• Texas A&M AgriLife Extension: Straight Talk About Iron Deficiencies

Resources

• University of Florida IFAS Extension: St Augustinegrass for Florida Lawns