Do you think it is too late to apply corn gluten today as a pre emergent. I live in Little Elm, TX. Average soil night time temp for the last two week is around 58. Last year i think the rain washed it away, because I have a ton of weeds.
Can I also apply the dry molasses and green sand with it?

It is too late - pre-emergents work if you put them out in December or right at the new year.

However, if you prepare the soil for planting in your garden and put in bedding plants, you can distribute corn gluten meal over the bare soil to discourage new weeds from sprouting. Cover that yellow layer with mulch and the bed won't be a bright yellow.

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Northwesterner