For heath balds the most obvious tree-killing agent is fire and so fire was advanced as an explanation for their origin. Shrubs can burn to the ground and grow back quickly, sprouting from their roots. Mountain laurel, rhododendron, blueberry, huckleberry, and sand myrtle all do this. It was theorized that where fire knocks out the tree layer, there are the heath balds. But the rub is that some balds show no signs of fire and yet are not nursing young trees. Landslides eliminate trees, and winter winds may also discourage tree growth. Heath balds persevere where slopes are steep, soil is peaty and acidic, and the elevation tops 1,200 meters (4,000 feet). Today the grass balds are a mosaic of shrubs, grasses, and young trees. Open patches may be clearly dominated by grasses but the total number of plant species present on grass balds is greater than the number present on heath balds. Explanations of the origin of grass balds have been much debated but no theory has been accepted for them all. We do know that most grass balds were used as high elevation pastures in the 1800s and early 1900s, and when the park was established the grass balds were more open than today. Most Southern Appalachian grass balds are being quickly invaded by trees and shrubs. The National Park Service is developing plans to keep two Smokies balds open. Despite their appearance, grassy balds have no floristic relation to true alpine or arctic tundra vegetation. [Illustration: The sundew, a bog plant common in the far North, persists on one grass bald, near a spring. What look like dew droplets are actually gluey traps for insects, which this carnivorous plant kills and absorbs.] [Illustration: Flame azalea thrives on grassy balds. At Gregory Bald it hybridizes with other azaleas, producing an array of colored flowers that botanists call a “hybrid swarm.”] [Illustration: When settlers grazed stock on the grass balds, many common weeds such as dandelions were introduced. Before settlement deer and elk probably grazed here, and may have helped keep out encroaching trees.] [Illustration: _The presence of trout somehow symbolizes wild nature and pristine beauty. Pools such as this one at the foot of Grotto Falls on Roaring Fork, are quiet forest gems that cause the finger of many an angler to twitch uncontrollably._] The Trout’s World