It wasn’t long after the oak tree arrived on the South Lawn of the White House, a gift from a World War I battlefield in France, that it suddenly disappeared.

The oak, which was supposed to be a symbol of a longstanding French-American alliance, had been placed in quarantine, because it was a living thing imported to the United States, the French ambassador said. It would be replanted, he said.

But that didn’t happen. Now, more than a year later, it appears we know why.

The European sessile oak had died, the French president, Emmanuel Macron, confirmed.

“It’s not a tragedy,” Mr. Macron said in an interview in Geneva with the Swiss broadcaster RTS. “One shouldn’t see symbols where there are none.”