Ships have unintended passengers
As ships travel across the oceans between the Americas, Europe, Asia, Africa and elsewhere they take with them unintended passengers. These stowaways include seeds mixed in with ballast.
In order to be properly balanced, cargo ships need weight, and if does not come in the form of goods then sand other heavy material is taken on and this is known as ballast. The US exported more raw goods and products to Europe than it imported for much of its history. This meant that a lot of European land was deposited on the shores of Red Hook, Brooklyn, as ships were arriving here not full of cargo.
Traveling with the ballast and taking root first at the Atlantic Docks and the mouth of the Gowanus was the plant Veronica beccabunga, also known as European speedwell or brooklime. Arriving around the 1840s and documented by botanists in 1879, it flourished in the marshy shoreline that then encompassed much of Red Hook, From here the plant spread across the country, but is no longer common in Red Hook as wet land was filled in with landfill.