Mystery solved?

After questions took root over what happened to the oak tree President Trump and French President Emmanuel Macron planted on White House grounds last week, the French president's office has an explanation: It was put in quarantine.

The sapling was a gift from Macron on the occasion of his state visit.

News photographers snapped away Monday when Trump and Macron shoveled dirt onto the tree during a ceremonial planting on the South Lawn. By the end of the week, the tree was gone from the lawn. A pale patch of grass was left in its place.

The White House hadn't offered an explanation -- but now word from Paris is the sapling is quarantined just like other plants or animals brought into U.S. territory.

An official in Macron’s office told the Associated Press Monday that Trump insisted on holding a symbolic planting ceremony alongside Macron despite the quarantine requirement. The official said both sides knew all along that the tree would go later into quarantine.

The oak sprouted at a World War I battle site that became part of U.S. Marine Corps legend. About 2,000 U.S. troops died in the June 1918 Battle of Belleau Wood, fighting a German offensive.

Reuters reported that the tree grew near the “Devil Dog” fountain. The nickname stems, in part, from the German moniker “Teufelhunden”, which means “devil dogs.”

It is reportedly believed that Germans used the nickname to descriibe the Marines who fought there due to their ferocity in the fight.

The Associated Press contributed to this report