Buckwheat is a short term crop that is best used for soil building. The saying is: "wet or dry, have it in by the 4th of July", so it may be a bit late. The first frost will kill it.
Cereal Rye on the other hand can be planted as late as Sept. It is the winter hardiest of all the grains germinating at 34 and growing at 38 degrees. It stores up nitrogen then releases it back into the soil when disked under. It also releases compounds that are harmful to the growth of weeds. Deer love it and it grows anywhere.
Genesis 27:3 Take your bow and quiver full of arrows out into the open country, and hunt some wild game.....