If you see smoke drifting from Valley Forge National Historic Park on Wednesday and Thursday, relax.  In fact, you might even want to pull up a camp chair and watch.

Park officials plan to burn 150 acres as part of its strategy to help get rid of invasive species that have degraded some of the 1,500 acres of meadows at the park. The vegetation can't easily be controlled by mowing or herbicide applications.

Jonathan Parker, a park spokesman, said it's expected most park operations and visitor facilities will operate as normal, though smoke may have some impact on traffic or force closure of some areas. However, the park spans 3,500 acres, so the burn directly impacts only 4 percent of its overall land.

The last prescribed burn took place in October 2014 as a pilot program, according to Parker.  Officials evaluated the burn and determined it worked enough to begin prescribing two burns per year — one in spring and one in fall — he said.

Fire operations will be scheduled to minimize any delays during commuting hours.

The park is planning burns at five different meadows along Route 23 (Valley Forge Road) and Gulph Road.

Officials have set up public viewing areas at Wayne's Woods, the National Memorial Arch, Varnum's Picnic area, and also the Von Steuben parking lot.

In all, 17 experts in fighting wild fires have been pooled to conduct the burn, Parker said.  Firefighters are being pulled from federal parks at Gettysburg, Shenandoah, and Delaware Water Gap, as well as the U.S. Fish and Wildlife Service.

Why now?

"April is a good time because the vegetation hasn't greened out yet," Parker said.