It isn't uncommon for a grocery store to carry popcorn, wheat berries, rye berries, whole (un-rolled, un-chopped) oats, brown rice, millet, buckwheat, amaranth, quinoa...as well as a few sundries like raw sunflower seeds in the shell, popcorn, breadseed poppy.
Pet stores
sell a mix of (usually) millet, sorghum, and sunflower.
This mail-order site came up on another
thread, and looks very interesting:
Quittrack wrote:you need to read "Small-Scale Grain Raising." It is most complete source when it comes to grain in the garden that I have come across.
I got my seeds from Bountiful Gardens http://www.bountifulgardens.org/
Their hard red winter wheat doesn't necessarily seem to be suitable for sowing in the summer, though.
Some are also available from the less-mainstream seed catalogs, usually under the category of cover crops. I know Baker Creek sells some, including mountain rice. A biodynamic catalog I looked through also had some grains on offer.
"the qualities of these bacteria, like the heat of the sun, electricity, or the qualities of metals, are part of the storehouse of knowledge of all men. They are manifestations of the laws of nature, free to all men and reserved exclusively to none." SCOTUS, Funk Bros. Seed Co. v. Kale Inoculant Co.