Hello Gardeners, I’m Amanda McNulty with Clemson Extension and Making It Grow. If you have lichens growing on in your yard, be delighted. They’re considered indicators of healthy air. They lack roots and get their carbon dioxide, water and all nutrients, except the carbohydrates the algal partner manufactures, from the surrounding atmosphere. As a result, air-borne pollutants become concentrated in them. The Forest Service has a program called the National Lichens and Air Quality Data Base to track changes in in our nation’s woodlands. They can see developing trends, take steps to address concerns, and measure the effects of changes in air pollution. While visiting the Olympic Peninsula in past years, we trekked under towering conifers draped with large but graceful cascades of a lichen called witch’s hair. Lichens can only grow in size when they are hydrated, the size of those organisms reflects the rainfall and moderate climate found in that temperate rainforest.