Chickens produce fertilizer, cultivate, and manage pests. As omnivores, they scratch the ground in search of worms, insects, and seeds. They also do not distinguish between my good plants and weeds. They will eat grass, weed, berries, fruits, vegetables, and tender new greens. They will eat whatever looks good. The only sure way to protect your garden is to limit their freedom.
My backyard has some spots that were weeds, but are now dirt. We found a moveable fence at a garage sale last year, so we are planning to reseed some areas. I could plant lettuce, cabbage, alfalfa, mustard, or kale as nutrient-rich greens. Seeds and grains like buckwheat, clover, cow peas, and annual rye would be good choices. Then, once the chicken garden is mature, I can take down the fence and let the chickens feast. An added bonus, the chickens will turn the garden spot into an enriched spot!
Some common plants can be toxic to chickens, too, including daffodils, tulips, bleeding heart, bracken ferns, delphinium, fireweed, foxglove, hyacinth, English ivy and nightshade. Lamb's quarter, milkweed and St. John's wort are also poisonous, along with shrubs from hydrangeas and Japanese yew to lantana and oleander. Inform yourself about other possible toxic plants in your area and prevent your chickens' exposure to these plants.
Be there to supervise if you want your chickens' help with pest control in the vegetable garden, because they won't distinguish between unwanted weeds and precious seedlings.