Purple in stalk and leaf stems

*note 1st time grow

It is now around day 50; Random bag seeds;
I’ve treated these 2,we’ll say A and B pretty much the same. In a grow tent, the same environment. Got a decent grow light from the grow store here in town its plenty for what I have maybe too much.

I notice the purple in the middle of a leaf first.
About a week later I noticed more purple in most of he leaf stalks in plant B.

Watered plant A and used micro grow and bloom as the bottle said. Left plant B alone for for 2 days. Watered plant B with just water(purified). Last watering for both was with distilled water before this one.

Now I have purple leaf steams in both plants and spots of purple in plant B’s stalk.

@JarJar welcome to the forum. That’s the beginning of a phosphorus deficiency by the looks of it. Are any of the lower leaves yellowing and dying too?

@MDBuds No discoloring and nothing is dying…yet that is.

is the color only on the portion of the stems that the LIGHT shines on or is it uniform all around the stems
what is the strain you are growing
where are your temps and ph at
did you have any issues with either ph or temps…temporarily?

@JarJar It’s either stress related due to light intensity or cold, nutrient related like @MDBuds said, could be a soil issue such as pathogens…, or it’s just part of its genetics… hope for the latter…:sunglasses:

@Mrb53004 It is mostly on the parts that the light shines on, but its also on pretty much every leaf stem and up and down the stalk but mostly on the new stalk growth.

  • Strain, I have no clue. just seeds collected from bags over time.
  • Temp low 66 once for just a couple hours; High 82. Regularly 74-79.
  • PH has been a slight hiccup. anywhere between low 5 and high 7 maybe even into 8 way earlier in the grow.
    Stopped using tap water, left sitting out over night and started with purified, distilled, and spring.
    Purified or spring when I feed; Purified or distilled(mostly) when I’m just watering.

*I got a “cool mist” humidifier about the same time this started to really show up. Its plant B that this is mostly happening to and it is not the one taking the brunt of the cold air from it.

the LOW temp and Ph hiccup could have resulted in the color change, so could genetics. At this point, I would watch the overall condition of the leaves and NOT the colors.
Cool mist - as we move more into FLOWERING, cooler temps (both air and leaf temps) can cause the terpines to begin to bring on the onset of WINTER. If the genetics of the plant include anything in the genus of strains with purple coloring, those terpines will trigger them. Sometimes that is GREATLY DESIRED!
If the plant/s LOOK good, do nothing. If not, wait a couple / 3 days and send new photo’s of concerned areas


If your leaves are healthy with no discoloration and it’s only on the portion of the stem that is hit by your light, then it’s basically a “sunburn”. I’ve had several different strains that would turn dark red/purple on the branches exposed to the light.

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