Snuggled into the border of the Garden for the Environment, by the corner of 7th and Lawton, a glowing mound of lemon-yellow, wooly foliage covered the ground for many years. The bad news is that licorice plant (Helichrysum petiolare) has been listed officially as an invasive exotic, and no matter how useful it may be in the garden, it is no longer an appropriate plant for environmentally savvy gardeners to grow.