Why Lawns in Northern Indiana Turn Rusty in Summer High Humidity and Lawn Rust Disease One of the most common reasons lawns in northern Indiana develop a rusty appearance during summer is a fungal issue known as lawn rust. Warm days, cool nights, and persistent humidity create ideal conditions for this disease, especially in mid to late summer. Rust disease coats grass blades with orange or reddish-brown spores that rub off easily on shoes, lawn equipment, or pets, giving the lawn an overall rusty cast. While it rarely kills grass, it weakens turf and makes it more susceptible to other stresses. Drought Stress and Slow Growth Periods of inconsistent rainfall or extended heat can also contribute to a rusty look. When grass becomes drought-stressed, growth slows dramatically, allowing rust spores to thrive and linger longer on the blades. Northern Indiana lawns, which are typically made up of cool-season grasses like Kentucky bluegrass and fescue, are especially vulnerable during hot, dry stretches. Without sufficient water, grass loses its ability to outgrow discoloration and recover quickly. Soil Nutrient Imbalances, Especially Iron Another contributing factor can be low available iron in the soil. While iron deficiency usually shows up as yellowing, it can combine with other stress factors to create dull, bronzed, or rusty tones in turf. Indiana’s soils can vary widely, and compacted or poorly drained areas often struggle to make nutrients accessible to grass roots during summer. This stress weakens turf color and overall vigor. Mowing Practices and Lawn Maintenance Improper mowing can intensify a rusty appearance. Dull mower blades tear grass rather than cutting it cleanly, increasing stress and making lawns more prone to disease. Cutting grass too short in summer also exposes soil, reduces moisture retention, and limits the plant’s ability to fight off fungal issues. Maintaining proper mowing height and sharp blades helps northern Indiana lawns stay greener and more resilient throughout the summer months.