COLONIE – Save the butterflies, burn the forest was the Pine Bush Preserve’s approach on Thursday.

The controlled burn creates the needed openings for the blue lupine, which is the endangered Karner blue butterfly’s only food plant while it’s a caterpillar, said Christopher Hawver, executive director of the preserve.

Fire rejuvenates the plants, which adapted to burning, Hawver said. “Nowadays you don’t have natural fires, or if you do they’re put out quickly. What we do is mimic natural fire.”

Besides encouraging vegetative growth, controlled burning of ground plants like scrub oak, wild blueberry plants and goat’s rue is intended to prevent more devastating fires.

“If we burn it, there is less of a chance of a real wildfire,” he said.

Thursday’s burn remained contained. Its smoke was directed toward the mall because it posed a greater risk in other directions, Hawver said.

Some nearby Crossgates Mall shoppers were left gasping for air.

“I walked outside of Crossgates and couldn’t breathe and I have asthma,” said Jim Grady, 41 of Glenmont.

Some controlled burns have grown out of control. In April 1999 a Pine Bush controlled burn scorched 75 acres and closed a stretch of the Thruway.