Just wondering if anyone out there has some insight into elongated stems on hydroponically grown lettuce. It is happening on all the varieties with exception of butterhead. The other varieties are Romaine, New red fire and lolla rossa. These are grown indoors with 100% artificial lighting.
I keep EC, pH under tight control.
I run lights for 14 hours/day
I keep the area cool and vent the light heat out
I also chill the root zone to ensure it never exceeds 70 F
The room temp and humidity stays around 73F with 62% respectively
When the stem forms, it will develop a milky residue inside it. This tells me the head is bolting but for the life of me I can't figure out why. All conditions say they should be fine. I have had the lights up as high as 17 hours/day but the long stem was still there. It did seem longer when the light was on longer but it did not decrease much after a 3 hour/day drop in light time.
I had read an article stating that lettuce may be programmed to bolt after a certain number of total light hours. ???? Is it possible that 14 is still too long and causing this issue?
Looking for input/advise.