The usefulness of corn gluten as an effective and non-toxic preemergent crabgrass control was discovered by accident. Searching for a cure for a fungal turf disease, Dr. Nick Christians of Iowa State University conducted experiments using cornmeal on his test plots. While his intended research goal was not met, the reduced growth of bentgrass on his test plots led to further testing, and a safe, environmentally sound preemergent herbicide was born.
What is Corn Gluten Meal?
A by-product of the corn processing industry, corn gluten meal is a powdery material that is available in three forms for home and garden weed control. Unprocessed corn gluten meal is a very fine, pollen-like powder, while granulated and pelletized forms are grittier and somewhat easier to handle and apply.
How To Apply
Powdery, unprocessed corn gluten meal can be spread by hand or broadcast with a hand spreader. It is best used on bare ground around newly planted shrubs and plants. Granulated corn gluten can be spread with a broadcast spreader to cover large areas of turf. It can also be mixed with water to form a thick, weed-suppressing paste for small areas. Pelletized corn gluten meal can be spread by hand and is best applied in spring as a "weed and feed" treatment for lawns.
Timing is very important when applying corn gluten meal. It is a preemergent herbicide and, according to the Iowa Horticulturist, "The corn gluten meal must be applied before the seed of the target weeds emerges above the soil." Typically, this is in early spring, between mid-April and early May. A late-season application is recommended to control perennial weed roots.
According to the Iowa State University Horticulture & Home Pest News, "CGM is labeled for use on turf, field crops, and home gardens. Among the weeds controlled with pre-emergent application of the product are crabgrass, dandelions, smart weed, redroot pigweed, purslane, lambsquarters, foxtail, and barnyard grass."
Corn gluten meal is non-toxic to humans, pets and wildlife. Because of its high protein content, it is used in livestock, fish and pet foods. CGM also contains nitrogen, a favorite food of lawn grass. Combined with its weed-suppressing capabilities, corn gluten meal is a safe, non-toxic alternative to chemical "weed and feed" products.
Corn gluten meal is more expensive than conventional herbicides, and it is, in some areas, more difficult to find in stores. Shipping costs on online or mail-order purchases can be high.
Excessive rainfall, heavy clay soils and high microbial soil activity can reduce CGM's effectiveness. Several applications may be needed for full control. In addition, weed suppression is not immediate. The effects of corn gluten meal are cumulative and require several applications for best results.