A year ago I wrote about discovering an organic version of Preen weed preventer that I was going to try in my vegetable garden. It utilizes corn gluten to prevent weeds. I applied it last July, and it did do a pretty good job of preventing new weeds among my lettuce, beans and peas, so I was happy. Until this spring, when in a OSU Master Gardeners ™ advanced training class I learned about some recent research on the effectiveness of corn gluten. We master gardeners are all about science and what is proven to work. As professor Linda Chalker of Washington State University explains in this cogent summary, researchers found corn gluten can be effective against new weeds in controlled conditions, but it is no more effective than good mulching, which is a LOT cheaper. And corn gluten isn’t very effective in the Western US if applied in the spring when conditions are moist. A five-pound container of organic Preen costs $15 at Home Depot. If you have materials like grass clippings, sawdust, or bark on hand, you can gain as much benefit by mulching well with those.