In 1986, a professor of horticulture at Iowa State University named Nick Christian, was conducting a fungus experiment on some plots of turfgrass. On one of the plots he applied corn gluten, a natural by-product of local corn milling. But instead of having any significance to his experiment, what he noticed was that seed germination in the plot with the corn gluten was significantly reduced.
Quite by accident, Dr. Nick Christian had just made one of the most important horticultural discoveries of the 20th century.
In Orange County’s Mediterranean climate, weeds germinate during two principal periods, early fall and early spring. Cool-weather weeds, such the ever-present Annual Bluegrass (Poa annua) that seems to grow just about everywhere, are about ready to germinate by the millions in our gardens. Soon you will again see this little weedy grass and other annual weeds in every walkway crack, invading lawns and growing throughout your flower beds.
So what’s a gardener to do about these soon-to-be-weeds? The answer; apply corn gluten now, before the seeds germinate.
Corn gluten works by prevention. All germinating seeds produce a first root, called a radicle and it is this that the corn gluten kills; it literally prevents weeds from growing. Plants that have already grown roots are not affected. That’s why the corn gluten needs to be applied now, before weed seeds germinate and grow roots. Wait to see the weeds and it’s too late.
As a pre-emergent herbicide, corn gluten has a cumulative quality and becomes even more effective on weed seeds after regular applications. It produces no ill effects to the garden, the gardener or the environment. Tests performed on areas with high populations of weeds such as annual bluegrass, crabgrass and dandelion, indicate that the weeds will be reduced by about 60 percent in the first year of application and 80 percent or higher during the second year. By the third year over 90 percent weed reduction was noted.
One application of corn gluten will suppress seed germination for about 4-6 weeks. In local gardens, I suggest a first application now and a follow-up application in 30 days. For spring germinating weeds make an application at the beginning of March and another a month later.
Corn gluten is a harmless, even edible material. It is so safe it even carries a rare “exempt” status from the Environmental Protection Agency. It is about the consistency and particle size of coarsely granulated sugar and can be broadcast to the soil by hand or with a spreader. Since it does not effect growing plants, it is applied right over the top of grass and other plants at a rate of 2 to 4 pounds per 100 square feet, then watered gently and left dry for a couple more days.
Especially important to local gardeners, corn gluten won’t foul our groundwater or polute Newport Bay or Crystal Cove; and it won’t pose a problem for our children, pets or wildlife. I know one gardener’s dog who enjoys licking the corn gluten off the blades of grass shortly after an application.Since corn gluten is a common ingredient in pet foods, good for him, he’s getting s a free meal. Use corn gluten on lawns, landscape beds, between stepping stones and anywhere else that weeds might germinate. You can even use it in vegetable and herb plantings, so long as you don’t plan on sowing seeds there during the next six weeks.
Since corn gluten also contains eight percent nitrogen, as much as many commercial fertilizers, it doesn’t just prevent weeds, it’s also an organic fertilizer. Some gardeners use corn gluten throughout the year as a sort of all-year weed and feed program. Corn gluten is available at most local garden centers and is sold under two or three different brand names. If you don’t see it, just ask.
Thanks Nick Christian, for making one of the most important gardening discoveries ever – by accident.
Questions from Readers October 3.
Ron Vanderhoff is the Nursery Manager at Roger’s Gardens.