im not sure if there is already a topic for this there may be, but i couldnt find it so...
first of all you need to extract your map(im my case modsource map v5), it helps if you extract the map into a empty folder for ease of zipping it back together
you will will be presented with this in your folder, next you have to open the map01.i3d circled in red open the map01.i3d into notepad or notepad c++
next you need to search for the line you want to edit so you click on, search in the top left cornor then find and in the box that appears on screen search for foliagesublayer
then when you have searched for this, you need to find this part <FoliageSubLayer name="grass", then go all the way to the end of the line and yo will find this
growthStateTime="1.8e+006"/> you need to change these numbers to edit the growth rate, im not exactly sure what the time scale is on this but i believe growthStateTime="4.5e+007"/> will give 750minutes before the grass re-grows
once you have done this you then need to compress all the files into a zip folder place it back in the mods folder of ls11 then off you go

REMEMBER all your friends have to have the exact same map for this to work in multiplayer so it may be best you send it them once you have done it
hope there isnt already one and i didnt find it
and thanks to STAINBY for helping me to do this in the first place
hope this helps
claasjaguar870
EDIT just realised i didnt put this in tutorials and guides if this is any good can one of the moderators move it there please
here are the times
500 milliseconds = 0,5 second
1000 ms = 1,0 second
10000 ms = 10 second
100000 ms = 1,66 minute
1000000 ms = 16,6 minute
2000000 ms = 33,3 minute
4000000 ms = 1,11 hour
15 minute = 900000 milliseconds
30 minute = 1800000 ms
45 minute = 2700000 ms
60 minute = 3600000 ms
75 minute = 4500000 ms
90 minute = 5400000 ms
18 hours = 64800000 milliseconds
24 hours = 86400000 milliseconds