The wreath that President Obama placed at Memorial Plaza yesterday came from a flower shop that had been at the World Trade Center on 9/11.

“We knew many of the people before the attack,” said Peter Grontas, owner of Flowers of the World, which had a shop at 4 WTC for eight years.

It now has a shop in the Financial District and one in Midtown.

Flower designer Colin Baer said it was a “two-day effort” to arrange the red roses and white and blue hydrangeas accented by blue hyacinth and green lemon leaves.