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Week 5 yellowing, N def or just natural fade?
Running a photo run right now, week 5 of flower, and i'm starting to see yellowing creep up from the lower fan leaves. Not dramatic, just the older stuff going pale and dropping. My gut says this is normal senescence starting, but i can't fully talk myself out of N deficiency either.
For context, i'm on a custom salt mix, currently running something close to a 1-0.5-2 N-P-K ratio by weight. pH is dialed at 6.1, runoff is matching. No other symptoms, tops look healthy and green, trichomes are stacking. But the lower third is definitely fading faster than previous runs.
What's the real tell for you guys? i know N def typically starts lower and works up, but so does natural fade. Is there a specific rate of progression or leaf color I should be watching for? Curious how others draw that line mid-flower before you start chasing a problem that isn't there.
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3 Comments
Expert Grower4d ago
week 5 with only lower thirds fading and tops stacking hard, that sounds fine to me. been there plenty of times and panicked over nothing.
the thing i watch for that nobody mentions is speed. natural fade at that stage is slow, almost lazy. you check monday, check friday, not much changed. N def that's actually a problem moves noticeably week to week and it'll start pulling color out of mid-canopy leaves that aren't even old yet. if your upper growth is still deep green and the new stuff coming in looks healthy, the plant's telling you what it needs to tell you.
your N ratio's actually not low for week 5. i run mine down a bit further than that by this point and don't see issues. so if anything i'd sit on it another week before touching anything. chasing a number mid-flower when the tops are happy is how you create the problem you were trying to avoid.
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Expert Grower4d ago
The speed test is genuinely useful and I use something similar in living soil. One thing i'd add though -- in a salt system, lower third fade at week 5 can sometimes be the plant pulling mobile nutrients back upward because it's not finding enough in the root zone, not just normal senescence. The tops staying green doesn't fully rule that out, it just means the plant is compensating well so far. Worth a close look at mid-canopy leaf color over the next few days before writing it off entirely.
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Experienced4d ago
The speed point from the reply above is solid, but there's another angle worth considering: check where the yellowing starts on the leaf itself. Natural senescence tends to go uniformly pale across the whole blade before it drops. Nitrogen pulling out under actual deficiency usually shows the interveinal tissue going a bit yellowy while the veins stay greener longer, at least early on.
Week 5 lower fade with healthy tops and trichomes stacking, I would not touch the feed. My bigger question for you is what your environment looks like, because out here in the PNW I've watched growers chase N deficiency mid-flower when the real culprit was temps dropping at night and slowing uptake. The plant looks like it's not getting fed when it's actually just not absorbing efficiently. Same visual result, totally different fix.
If your pH is truly locked at 6.1 with matching runoff, deficiency from lockout seems unlikely. Anyways, the lower third going first at week 5 on a photo run is pretty textbook. I'd watch the rate for another week before second-guessing yourself.
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