For about 120 years, the textbooks were sure of it. Purslane was an introduced weed that came over with European colonists. Asa Gray wrote it down in 1848. Case closed.
Then people started digging, literally. Purslane seeds turned up in lake sediment in Ontario dated to the 1300s, before any European set foot there.
More seeds came out of a Kentucky cave, left behind by people who were also growing squash and sunflower 2,500 to 3,000 years ago. The plant was here and people were already eating it long before anyone sailed the ocean blue in 1492.
So which is it, native or invasive? The answer is interesting, because it's both.
Purslane isn't one tidy species. It's a sprawling complex of plants, and the evidence points to some lineages being ancient American residents while others really did arrive later with Europeans.
The USDA's own database lists it as native and introduced at the same time. How the earliest version got here, nobody knows. Birds might have carried it, but it's hard to say.
"Native" and "invasive" feel like hard categories, but the line gets blurry fast. Not everything green in your yard sorts cleanly into good and bad.