hi chris
here is what you should do!
go to the garden center and buy some water cress seeds,get up really early when its still dark,get to your permission while still dark.and take the top soil out about an inch deep and ten square meters in size,plant the water cress seeds.give them a watering before you leave,and pop back at regular times (while its still dark) for a fortnight and top up with water,weather depending.once the water cress has grown to about (70mm to 100mm - 2 1/4 inches to 4 inches) for those who shoot in metric & imperial.
get to your location before sun up,and ge