I have received e-mails every day now from both professionals and home owners–about corn gluten meal–To put it down now–or— to not put it down- and what if it rains real hard after the application— are the main questions.
With corn gluten meal- especially in the Spring- these questions are always looming. here are the pros and cons–-if the dandelions are blooming then it is time to do it—you have to know that the weeds you see now had to have be controlled last fall- (or if you see them now they weren’t) the whole idea is to put the corn gluten meal down to catch the seeds that are blowing now that will show up later (in another1 1/2- 2 months). If the corn gluten meal isn’t on the ground when that happens then you will get more weeds.
Remember that it works long term only because it bonds with the soil—and because of that– if it rains enough to wash the soil ( erosion) then the treatment has washed away with the soil–so after heavy rains that do a lot of washing–yes you would have to reapply it-unless the heavy rain fell in the heat of a hot summer.
This problem will differ with different sites–some sites have bad erosion problems due to poor drainage or lack of gutters or sloped areas– or what ever –Be sure that you water over the corn gluten meal lightly to bond it to the soil at the time of application- or it will blow away–If you have gutters–good drainage and a property that does not suffer from bad erosion-it will work out great- and rain will not ruin the process.
I say over and over that well graded-well drained properties with gutters are going to give you the best over-all gardening experiences–whether it is weed control-fertilizing or disease control–no products will make up for poor drainage.
Weeds often get carried to back yards that have privacy fences because they float under the fence from a neighbors yard and get started along the fence-then blow into the rest of the yard– or wash into a low spot and germinate there. I see this all the time–a weedy yard will always have one spot where they are the thickest–that is where seeds washed and got started–that spot will prove out to be a low spot every time–even if the weather is dry when the weeds are going strong–the one time it did rain and the water set there in the low spot where the seeds accumulated and they germinated–that often is what gets weed problems started. So get those depressions raised with top soil now-and apply the corn gluten meal —and in the case of the weeds starting along a fence line because seeds are washing under the neighbors fence due to over watering on their part or drainage issues on their side–use edging along the fence line to stop the flow of the water into your property-be sure that the edging goes below the soil line and slightly above the bottom of the fence. With this in mind-if you are putting in new privacy fences opt for the concrete footing–it costs more up front but makes the wooden fences last longer and keeps water & weed issues at bay.
Be sure that it is understood that corn gluten meal does not kill but helps to deter weeds—- if you don’t put it down–the weeds will be worse then if you do put it down—the hard truth is that it is not fool proof for all the reasons above-but right now it is all we have that works well with other factors (mentioned above) in place–and it won’t pollute your water , ruin your health and the health of your pets or create havoc with the environment.