Collard is a group of certain loose-leafed cultivars of Brassica oleracea, the same species as many common vegetables including cabbage and broccoli. Joel Grossman's archeological findings in lower Manhattan show that brassica seeds were indeed present in New Amsterdam. This would have included cabbage, and likely collard greens. Cabbage was grown in Holland extensively, and collard greens would probably have come to the settlement along with the enslaved Africans.
See a detailed article on the archeology of plant life in New Amsterdam by Joel Grossman, PhD. here. Courtesy of the Holland Society of New York.
For additional reading see Environmental History of the Hudson River by Joel Grossman, PhD. https://www.geospatialarchaeology.com/Indices.pdf