Week 5 yellowing, N deficiency or just natural fade?

Running a hypothetical here because I want to understand the logic before I'm staring at a plant at midnight second-guessing myself. Say you're at week 5 of flower, lower and mid canopy leaves start going yellow-green, no spots, no interveinal anything, just uniform fading. EC is around 2.1, N in the feed is sitting at roughly 150 ppm as part of a 3-1-2 ratio. Do you chase it with more N or do you call it a fade and leave it alone? My instinct says week 5 is a little early for true senescence fade, that usually picks up around week 6-7 depending on the strain. But i've also read that some faster finishers start pulling from fan leaves earlier than expected. The tricky part is that genuine N deficiency and early fade look almost identical in the early stages. What signals are you actually watching to tell the difference? I'm thinking rate of spread matters a lot, like if it moves fast up the plant it's probably a deficiency, slow crawl from the bottom is more likely fade. But curious if anyone has a better diagnostic approach before reaching for more calcium nitrate.

3 comments

3 Comments

Experienced1d ago

The rate of spread thing is real but i'd add one more signal people skip: check what the yellowing leaves actually feel like. Deficiency leaves go limp and papery fast, sometimes within a day or two of showing color change. Fade leaves hold their structure way longer, they yellow but stay stiff. Run your fingers along them. Also 150 ppm N at week 5 with a 3-1-2 ratio isn't low at all, so if you're genuinely seeing rapid upward spread AND limpness, i'd look at root health or lockout before i blamed the feed numbers. Chasing it with more cal-nitrate at that EC could create more problems than the yellowing itself. The strain variable is the thing everyone in this thread is probably glossing over. I've run terp-heavy cultivars that strip their lower canopy aggressively by day 30 and it looks alarming but the buds finish perfect and the cure smells incredible. Then i've run other phenos of the same cross that hold green til day 60. You really can't call it without knowing what the plant has done historically.

Expert Grower1d ago

Rate of spread and leaf feel are both valid tells but nobody's mentioned the upper canopy yet. That's where i look first. Lower fan leaves going yellow at week 5 with healthy upper growth and tight bract stacking, i'm not touching the feed. That's the plant doing what it does. But if the new growth at the top starts looking washed out or pale at the same time, different conversation entirely. 150 ppm N in a 3-1-2 at 2.1 EC is not a starvation number. Been running outdoor at similar ratios for years and the plants pull from below on their own schedule. One thing i'd actually watch is bud development during that week. If the yellowing coincides with a visible swelling push, the plant's prioritizing. That's normal. If the buds look stalled and flat while the leaves fade, then something's off.

Expert Grower1d ago

The upper canopy check is solid advice. One thing i'd add from a soil biology angle is that uniform lower fade at week 5 often coincides with mycorrhizal networks actively redistributing phosphorus toward the developing buds, and the plant is essentially cannibalizing mobile nutrients from older tissue on purpose. In living soil i've learned to trust that process more than i used to, because the microherd is usually ahead of what any ppm reading tells you.