I know for sure our stuff is homegrown and organic.
You can just tell...once you get a taste for the homegrown organic high (hehehe) quality herb, you know right away if it's not. Especially if you use a vape. You can taste the pureness and fresh flavor of it; aromatic...fragrant MJ will not be hard to distinguish, especially if you know what kind of MJ it is..and then you can taste the undertones of those flavors as well. When you get swill...you can taste the nasty, harsh flavor of it and moan about it to your vaping buddy
Also, once you are at that point, it's quite easy to tell by the way you feel after you use your MJ. By then you'll know the difference from a high quality Indica and Sativa strain. When you use the dirt or nasty stuff, you'll know it right away! It's terrible compared to the good stuff! You can also tell by looking at it. Like dp (self proclaimed MJ connoisseur) says...if it's homegrown organic stuff it won't have seeds (only mass produced commercial crap does), no harsh aftertones, and you'll be able to see the difference by seeing hairs and crystals visibly on the herb. Flushing your plants out for the last 2 weeks before harvest and ample drying time is how to get the fresh, smooth, fragrant tasting herb...and only homegrown organic (most of the time, anyway) growers do this and take the time to do this b/c they care about the herb they are producing and are out to grow high quality beautiful bud.
As for nursing...my biggest concern would not be the THC, for reasons mama516/419 explaines so well...but the chemicals used on the herb and toxins from inhaling smoke. My best advice...as often as possible use homegrown organic stuff and always vape if you can. But I think that's a given