[tyler12]

Something like:

pawn Code:

if(IsPlayerInRangeOfPoint(playerid,20.0,WeedInfo[weed][WeedX],WeedInfo[weed][WeedY],WeedInfo[weed][WeedZ])) return SendClientMessage(playerid,-1,"ERROR: You can't plant more weed here.");

Just loop through all the plants and check if the player is in range of any of them.