5% iron supplement. Give your plants a shot at greatness with Bush Doctor® Liquid Iron! Iron is essential to plant growth, playing a vital role in green up, energy production, and nitrogen fixation. Bush Doctor® Liquid Iron is like a nutritional supplement for your plants, giving them a source of iron when they need it most. You wouldn't train for a marathon without taking a nutritional supplement, would you? For use on trees, shrubs, citrus, and roses. OMRI Listed® and Registered CDFA Organic Input Material.