Have been using corn gluten meal for a fertilizer and weed supressant since May. Although some weeds have disappeared, I still have a problem with black medic. I have been told that it will take a year or more for the corn gluten meal to be quite effective. Is there anyone here who has used it for more than a year, and thus, can tell me what to expect in terms of getting rid of weeds?

While corn gluten prevents seed germination there wont be any effect on established plants, black medic in our area can either act as an annual or bi-annual weed so that is why it may take a few seasons to control. Medic is easy to pull at this time of year though so give that a try or spray them with white vinegar.
In my organic lawn service I take a different route, instead of using corn gluten to prevent seed germination I prefer to overseed every season, fall, spring or both if need be, this way my customers money is going towards thickening up the lawn which every one wants anyways and the benefit being that future weed seeds have a difficult time germinating and establishing themselves.

>While corn gluten prevents seed germination there
>wont be any effect on established plants, black
>medic in our area can either act as an annual or
>bi-annual weed so that is why it may take a few
>seasons to control. Medic is easy to pull at this
>time of year though so give that a try or spray
>them with white vinegar.
In my organic lawn
>service I take a different route, instead of
>using corn gluten to prevent seed germination I
>prefer to overseed every season, fall, spring or
>both if need be, this way my customers money is
>going towards thickening up the lawn which every
>one wants anyways and the benefit being that
>future weed seeds have a difficult time
>germinating and establishing themselves.

I have been handpulling a bit, and it seems to be working. I don't want to shoot it with vinegar because I don't want to make the soil more acidic. In fact, although I don't use salt on the sidewalk in the winter, the city and some of my neighbours do, so I am getting a bit of crab grass and other weeds that like acidic soil. This year I am going to try gypsum on a one foot strip by the sidewalk and especially on the boulevard strip between the sidewalk and the road. Apparently it will correct the saltiness/acidity and also help the compaction, which is something I cannot do anything about when the city piles the snow by or on the boulevard strip.

Yes I know GTA soils very well and you are on the right track Marge. I would recommend a core aeration before gypsum application, but be aware that gypsum will not affect the ph factor. For that you need lime or even better an annual application of compost.