Many of today’s typical cove hardwood trees have also been found as fossils in rocks of Cretaceous age in the eastern United States. This match up—and the recognition that the southern mountains have been continuously available for land plant growth since Dinosaur Days—has given plant geographers much food for thought. Cove forest is now plausibly regarded as a very ancient mixture of species. Probably, it was the ancestor of several other widespread forest communities. Perhaps it was the haven of refuge sought by many plants and animals during the Pleistocene glacial period. Its significance today is its wealth of species composition and its heritage—millions of years of forest evolution. We are fortunate that significant stands of this forest type survive uncut in the Great Smoky Mountains. A great benefit of these rich, lush forests for hikers is the refreshing coolness they afford on hot summer days. Many people have described them as “green cathedrals” because of the coolness, rest, and peace they seem to engender. [Illustration: When the yellow-poplar seeds into an abandoned farm field it means that the field could eventually become a cove forest. But the yellow-poplar needs the company of a dozen other species to form true cove forest.] [Illustration: The yellow-poplar grows fast and straight. Its bark has white-sided ridges.] [Illustration: Cove forest has less moss cover than the spruce-fir forest, but it boasts more kinds of mosses. The abundance of trees, flowers, and lower plants is produced by ideal moisture and a temperate climate.] Forest Openings: The Balds [Illustration: Bald] Most mountains show mosaic patterns of vegetation noticeable at a distance, or on scenic postcards. In the Smokies high country this zoning is conspicuous. These mountains rival the Rockies for all such contrasts, except for naked rock above timberline. There is no climatic treeline—roughly an elevation above which trees cannot survive—in the Smokies. But two important treeless communities, called “balds” by the early settlers, give this above-timber effect here. The baldness is not that of bare rock, but rather a mountain-top interruption to the forest cover. The two types, grass balds and heath balds, are alike only in appearance from a distance, and in their preference for mountain summits. The Cherokees wove the balds into their religion and folklore. Mountaineers grazed stock on the grass balds and cursed the heath balds as “slicks” or “hells.” Botanists began to publish explanations for these balds a century ago but you can still formulate your own theory because there are no agreed-upon answers. The more careful the study, the more puzzles arise. But the key in both cases seems to be _disturbance_, the successive destruction of generations of tree seedlings.