Corn gluten meal is an all natural product- a by-product of corn milling- used in a variety of cooking recipes.
Researchers discovered that when applied to soils, it stopped the newly-emerged radicle (small newly emerged root from the seed) from orienting itself and establishing itself in the ground. In short, this milling-byproduct does not stop seed from germinating but it does stop them from establishing themselves. So, the seed tries to grow but can’t.
Corn Gluten Works On…
This works on all small seed. But larger seed such as corn and beans tend to have large radicles and enough energy to push that newly emerged root past the layer where the gluten sits.
It does work on the majority of lawn weeds such as dandelions and crab grass.
It also works on some small weed seeds in the flower garden (including flower seeds) so it can be used but not if you sow your own flower seeds
Note – corn gluten won’t kill this patch of dandelions. It doesn’t work on established weeds.
It Does Not Work On
Established weeds – this product doesn’t have any impact on established weeds (much like any chemical pre-emergent that only works on small, just-germinated seeds)
It is less effective on large seeds than small ones.
When applied at the rate of 20 pounds per 1000 square feet of garden, it will stop emerging seed from growing.
This has to be done before the seed emerges as (like any pre-emergent chemical) it has absolutely no effect on established plants.
The indicator plant is forsythia. When the forsythia bloom, apply the meal.
There are also university recommendations to reapply in mid-August to stop newly shed fall-germinating weed seeds.
If used on a lawn, it will also stop grass seed from germinating so do not topdress with new seed and apply it (the same holds true of pre-emergent lawn chemicals.)
This organic weed control product is effective for 5-6 weeks although the data on length of efficiency is still being researched.
Naturally Feed and Weed Your Lawn
It also contains 10% nitrogen by weight. This means if you put 20 pounds of the meal on your lawn in the spring, you’re applying 2 pounds of nitrogen.
This is all the nitrogen your lawn requires at this time so you can eliminate the use of a spring fertilizer if you use this material to eliminate weed seeds.
If you apply a mid-summer application to control late germinating weeds, you’ll have applied 4 pounds of N to the lawn and this is more than enough to feed the average lawn.
How To Totally Eliminate Lawn Weeds
On lawns- it will take 4 years or so to get control of weeds. Remember that it doesn’t kill existing weeds, it only stops the new ones.
So you have to remove established weeds.
Think of an incremental type of control- year one it will control a few- year two there will be fewer survivors and by year 4 or 5, you should have good control.
If you top dress in the fall late September, the new grass should be well-established enough to survive both the winter and the spring application.
General Garden Use
In the garden generally. Corn gluten is safe for use around shrubs and established plants.
With starter pack-plants, they are big enough to handle corn gluten meal.
Remember that this meal is on the surface and the larger pack plant roots are already well established. If concerned, plant pack-plants a week before spreading gluten on the garden.
Do Not Apply To Vegetable Gardens If…
Vegetable seeds (with the possible exception of corn and beans) will be stopped cold by corn gluten so it is not recommended for vegetable use.
Problems with Corn Gluten
You have to water it in thoroughly to get it to spread across the surface of the soil. Failure to water it in is a big cause of dissapointment in the product.
Having said that, if it rains a lot in the first two weeks after application, it will be dissolved (so would most chemical applications) and it will be less effective.
In organic soils with high levels of beneficial bacteria (or if you’re applying lots of compost) the corn gluten meal will be attacked by the bacteria because it contains 10% nitrogen (nitrogen being a prime food source of bacteria).
So the active time might be somewhat shorter on really good soils. But I note that the better your garden soil- the fewer the weeds you’re going to have anyway.
Dangerous to Humans?
Is it dangerous? Humans have been eating it as a staple food source for a millennium. Need I say more?