The tree species known only as Pennantia baylisiana could be the rarest plant on Earth. In fact, the Guinness Book of World Records once called it that. Just a single tree exists in the wild, on one of the Three Kings Islands off the coast of New Zealand, where it has sat, alone, since 1945. It didn’t used to be so solitary, but humans introduced goats to the island, which ate every other member of its species.
Over the last few decades, scientists have tried to create more P. baylisiana trees, but aside from getting cuttings to grow, simple biology got in the way: The tree was thought to be female, and it appeared to need a male to properly generate fruit and seeds.