What are the current thoughts on using corn gluten to discourage crab grass?
Question:
What are the current thoughts on using corn gluten to discourage crab grass?
Answer:
The UNH Extension has a great resource for homeowners on controlling crabgrass, including a nice summation of the corn gluten situation:
“Some gardeners swear by the use of corn gluten as an organic pre-emergent herbicide, but university research to support its effectiveness is inconclusive. Research data show mixed results, and some studies have found that corn gluten does not work especially well against crabgrass. Corn gluten typically contains about ten percent nitrogen, and this fertilizer may help green up lawns and result in dense growth that out-competes weeds. Yet, it may contribute to ground and surface water contamination depending on the application rate and any other fertilizer products used. For weed control, the established recommended rate is 20 pounds per 1,000 square feet. At this rate, about 2 pounds of actual nitrogen are added to the lawn. However, New Hampshire’s turf fertilizer law allows no more than 0.9 pounds of actual nitrogen to be applied per 1,000 square feet per application. Thus, applying corn gluten at a rate that may suppress weeds puts the applicator on the other side of the lawn and may cause environmental harm. Corn gluten can certainly be used as an organic nitrogen fertilizer as long as no more than 0.9 pounds nitrogen per 1,000 square feet are applied at one time, not exceeding 3.25 pounds of nitrogen in a year.”
The Maine turf fertilizer rules are slightly different, but the real takeaway here is that studies haven’t demonstrated effectiveness for the treatment. I recommend using the alternate methods of control from the UNH link above.
Happy gardening.