When the 1994 World Cup came to the Silverdome, games were played on natural grass rather than the stadium's artificial turf (also fondly known as concrete painted green). Despite the Silverdome not being an open-air stadium, Michigan State University developed grass that was able to grow indoors, and it was placed on wooden pallets on top of the turf (per Wikipedia).
When the 2011 CONCACAF Gold Cup comes to Ford Field in June to host a pair of games, including the United States vs. Canada, the playing surface will be natural grass. I'm not quite sure what the process is for putting in the grass, but I would imagine it will be similar to what the Silverdome did last summer when it put down grass for a game between Panathinaikos and AC Milan.
The grass laid down for the match on top of the synthetic field wasn’t perfect, Onyewu said, but it was good enough if it allowed these two teams to compete in an area that may not have gotten a match before.
"Obviously, playing on a field like this is not the same as playing on a natural grass surface. You know, but they did their best. Obviously both teams had to play on it, and we adapted to it."
Added Milan coach Massimiliano Allegri, "Obviously the field slowed the game down a little bit, especially because it was kind of like carpet put down on concrete. But it was still a good game and there was some good technical action during play."
The grass used in the Silverdome back in 1994 needed to be in use for a week and a half, whereas the grass at the Silverdome last year was for one match. The grass at Ford Field will host two matches in one day, so it won't need to be a long-term thing. In that regard, it will be interesting to see how effective it is, and at the very least it will be interesting to see a grass surface in Ford Field.