Quick growing grass

I need some grass that will germinate and start growing in about a week. I don’t need a full lawn (it is to show the effect of oil dumping on plants) but it does need to be a decent length to show the results. What do I want to go with? Either generic or specific (e.g. Scott’s turf builder) will work.

Hard Winter Wheat:

rye will spout in 2 to 3 days and emerge quickly, within the week.