It varies by strain and growing condition. That's always a given though. Also, the potency is completely based on my own judgement. Trust me, I have enough experience to tell how my body's reacting. Also, this is for indica and hybrid strains, that have a cloudy stage.
Generally, as far as I've noticed, the main cola's not necessarily any more potent than the rest of the plant. The trichomes tend to be more or less developed; but the potency, overall, seems to be the same. Let me explain. On my plants (Doesn't seem to matter if I top, L.S.T., or let it hang out all natural like) the bottom part of the main cola(s) and the buds just below seem to be more mature. Sometimes some of the very bottom buds on the plant will mature faster, I guess since they grew first. However, They never seem to finish as well as the middle buds and the bottom of the main cola. That's most likely a light issue. So, results from outside grows may be completely different. Here's a breakdown of how it seems to be working out for me, based on when I harvest.
Early harvest (Trichomes fully developed, but still clear... maybe starting to get a little cloudy):
The main cola's usually not potent toward the top at all. The rest is so so. If you want to tarvest at this stage, it shouldn't be for the larger cola(s). It's for the general uplifting high. There tends to just be a good burst of energy for a short amount of time and then it just wears off. It could be a strong high, depending on the plant, but it generally won't sit you on your back side and there's no real "come down" period. It just kind of goes away at some point, leaving you wondering where that high you just had went to. A.K.A. "Oh great just googly it, I'm not high anymore... damn..."
Mid harvest (Trichomes cloudy... maybe a few clear, maybe a few amber):
This is where it's at for me! Most of the main cola is indeed more developed and actually, contradictorily, a little more potent. The very top of the main cola, as usual will be less potent. It's new growth. it pretty much has to be. This will uplift you for a bit, give you a good after glow, and possibly sit you on your back side. As a side note, if you cure for a while, the very top of the main cola will usually mature. That's why I consume my colas from the bottom up or middle out now -- middle out is better.
Late harvest (Trichomes going past cloudy):
Yup, the cola will be really mature and stony if you let it get that far. The rest of the plant will likewise be really mature. Even the bottom light scrounger buds will usually be at least very milky, if not fully ripe (Possibly over ripe). The actual potency seems to still be about the same all over. The high changes to more of a stone or mellow. It actually seems less potent to me than full cloudy. But it doesn't matter much. You won't want to move to do anything about it. You'll just sit there content and contemplating your current situation.
Really/Over ripe harvest (Trichomes mostly amber):
I've only done this once; so I can only give experience with that. It wasn't potent enough for me, and I didn't like the all out stone. It was a weeker stone, and I didn't want to move to do anything about it... totally different from the above nice stone that I didn't really want to do anything about. I just had this overwelming feeling that I needed to somehow rectify the situation. The bud was for friends, for a 420 party. I really took time to grow and cure it. it was a perfect bud; about eight to ten inches dry... and thick. Adult sex toys should be modeled after this thing. To note, my friends loved it. Honestly, I think it was a little of the bag appeal that did it for them. I may try again later, but for now I'll stick with partially to full cloudy. This was White Widow, by the way. The buds I sampled earlier were great, so it wasn't the plant. I just let it go too long. Also, don't get me wrong. it was still definitely strong... just not strong enough to make the stone enjoyable. I just felt lethargic and not at all social.
As for sativas and any plant that doesn't have a real cloudy stage... I've only had the pleasure of growing a few of these. In my experience so far, it's the same deal, except that the longer you wait to harvest the better the high. I've yet to get one of these to be over ripe. It's hard enough to wait for even a little true amber. So, you'll have to wait for someone else to chime in and give more info for your sativay plants.
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