VALLEY FORGE, Pa. (KYW Newsradio) -- Motorists who travel on Route 23 near Valley Forge National Historical Park may be seeing some smoke in the area over the next couple days. The national park will be burning 150 acres to reduce invasive plants that are pushing out native varieties.Jonathan Parker, with the National Park Service, explains which plants need to be removed."There's four main plants, like oriental bitter sweet, Japanese honeysuckle, wineberry and the callery pear," he said.