How to build up stem strength (thickness)

if the internodal spacing isn't too large, it is genetic. If the nodes are far apart, you need more light. That will get them thicker and shorter node distances - tied together. I've heard silica helps? it's just genetics and lighting 90-99%, though. Assumes you provide all the nutrients a plant needs and in proper ratios/concentrations. kinda a crapshoot in organic gardening. could be self-inflicted and there's no easy way to deduce if that's the case. I have 6 different strains growing in my vege area. There is a drastic range in stem thickness, growth , everything among them. This is most likely just normal for those plants, because they don't look stretchy in your pictures... just my 2cents.. you can see better in real life. Sometimes a plant gets floppy.. light smight be too close? i see it sometimes when i bring a smaller plant into my bloom box. The first day it acclimated to the increased lighting and is a bit floppy.