Line-trimmers are great for grass but can be deadly for trees. A peek inside a tree shows why. Bark is composed of a protective, corky outer layer and an inner layer of phloem, which is essential for transporting sugars. In general, the phloem's tube-like cells carry sugars manufactured in the leaves downward to nourish trunk and root cells. A line-trimmer can easily cut right through bark, especially if the bark is thin. Once the tree's nutrient-transport system has been severed, the roots will slowly starve, and the tree will die. Protect your tree from accidental nicks by cutting a circle in the lawn around it and mulching the root area, or use plastic tree guards that expand as the tree grows. With more than 30 years experience in horticulture in B.C. – in wholesale, retail and at VanDusen Botanical Garden for a decade – Carolyn Jones brings a wealth of knowledge and expertise to GardenWise and www.gardenwiseonline.ca as staff horticulturist.