Somewhere outside Antioch, California, which is about 40 miles northeast of San Francisco, there lies a patch of wildflowers so rare that botanists aren’t disclosing their location, for fear of tourists or vandals. 

The wildflowers, known as Mount Diablo buckwheat, or, by their Latin name, as Eriogonum truncatum, were thought to be extinct for nearly seven decades, until a small patch of them were found in California in 2005. 

But the latest discovery, according to the San Francisco Chronicle, is much, much bigger: some 1.8 million flowers, large enough that botanists are hoping it will provide clues as to how to make the wildflowers more sustainable in the future. 

Botanists have refused to say exactly where the flowers are located, and even held back from disclosing that they found the Mount Diablo buckwheat for several months before making the announcement on Wednesday. 

That’s mostly because the flower has been called a “holy grail” for botanists, because of its rarity, but also because of its illustrious past. It was first discovered in 1862 outside Brentwood, California—not far from the latest discovery—but seemingly disappeared in 1936, and was presumed lost forever. 

But a student found some in 2005, marking the flower’s comeback, though it has largely resisted efforts to reintroduce it into the wild, making the discovery all the more remarkable. 

“I had personally hoped to find this thing for so many years, and then I suddenly walk up to this population that was so numerous,” botanist Heath Bartosh told the Chronicle. “It was like, wait a minute, this can’t be real. I’m dreaming.”