the cops need probable cause to get a warrant. they have to demonstrate to a judge you are committing a crime with whatever couple shreds of evidence they present to him/her....multiple complaints of smell, a couple arrested snitches say they are buying from you(easy to fake), fertilizer bags in your trash, etc. these things have to be able to be casually observed. however, with the implementation of the patriot act, designed to let law enforcement cut corners to go after terrorists(because who doesn't want that right.) instead, the overwhelming majority of the time the patriot act has been used, it's to prosecute "crimes" that have fuck all to do with terrorism. that is why i previously mentioned jury nullification as a means to beat that crap.
i've sat in the next room and heard cops lie to a magistrate, outright lie, to get a warrant. because their goal is always going to be throwing your ass in jail and if they can't play by the rules and do just that, they will settle for simply fucking with you.
1-if the cops are able to go by the book and get a warrant and hem you up, you weren't careful enough and barring a fanfuckingtastic lawyer and a stroke of luck, you are fucked.
2-you might have left some shit unattended to and the cops through no hard work of their own happen upon some chance discovery of circumstantial evidence that no judge would ever issue a warrant for, they will makeup evidence that will never be presented as such, and by the time they need to prove their case in court, you've already paid bail, paid for a lawyer, lost all your grow equipment, lost all your plants, they've destroyed your property....and the case is dropped. you get none of that back. mission accomplished, the prosecutor has spent zero effort to send you up and you are most likely left severely fucked with. sure you could sue, but most don't because that process just left them ruined.