How we protect our trees from deer! Here at Stark Bro’s, we protect our trees in the nursery with Tree Guard®, which contains Bitrex™, the world’s most bitter substance, according to The Guinness Book of World Records! In testing with deer delicacies, Tree Guard beat homemade remedies and other deer repellents on the market. Ready-to-use, requires no mixing. With one application of this new latex formula in fall, you’re set for up to 100 days. In spring, new growth should be treated. Non-toxic to humans, though not for use on vegetables. 1 gallon.