If you plant Sumac make sure you are not allergic to it it is like poison Ivy, and poison oak. and it spreads fast or in my area it does.Is your friend free ranging his birds or does he keep them in a moveable coop? Birds not kept in a coop will hustle around and find alot of their own forage.That's the beauty of the heritage (old timey) breeds; they were developed at a time when people expected their birds to go out foraging and find at least part of their own grub. As to what to plant, I'd check with the state Department of natural Resources or the Audubon Society. Pretty much any native shrub or plant that provides food and cover for wild birds (especially ground birds like turkey, quail and pheasant) will be appreciated by your chickens as well. Depending on your state's budget, you might be able to purchase native plants inexpensively, it's worth asking about. Remember too, that plants that are attractive to insects are good, because your chickens will spend many happy hours chasing down bugs. Compared to the average suburban lawn, you'll be planting alot of weeds.But right off hand, I'd suggest sunflowers, holly (native and evergreen european varieties), and Sumac.