I don’t know but I cannot wait to see if any of the clones behave the same way. Please keep this thread alive and let us know?
A hollowed out stem is the result from the plant undergoing Pith Autolysis to retrieve more carbon for photosynthesis in times it needs it. You can safely view a hollowed out stem as a pseudo Carbon deficiency and that there were times in the plants life cycle it needed more carbon.
With some plants, it is genetics. When that is the case, the plant needs SUPPORT to prevent it from collapsing / breaking
These are mother daughter pics with clones from the flat branch tree on the left in solo cups and the one on the right is sister plant and her daughters that was planted 2 weeks after the flat plant but both sets of clones cut at identical times. Flat tree clones are bushing just like the flat branch itself did.
if it is genetic, you do not need to prevent…they just need SUPPORT. Hollowed stems are / were a good sign not something bad. Carbon is added by having good organic soil and adding compost / mitochondria (beneficial bacteria)
The ww girls and their twin clone daughters. The one on the left is the flat branch but I chopped the flat branch off and the right is from same source but planted 2 weeks later.
The clones Hermed out so I had to chop and toss them. 
looks like somethings been eating it any deer or rabbits around
No these are all in tents indoors
I did notice the tips on the right side plants (toddlers), they show wind burn so you might want to lower fan speed or tilt up a little. Not sure you need that much airlfow as you have your plants very trimmed
Thanks man. I have been waiting for 3 months for this company to replace the 2 oscillating fans that only lasted 30 days a piece. I’m getting fed up.
@Chicojackson to add to what @Mrb53004 said it’s possible that it’s a fungal infection as well. I see some gray and brown decaying pith material in the hurd around the xylum. Looks like fusarium proliferatum/oxysporum infection causing pith necrosis. Commonly called fungal wilt or fusarium wilt.
Aside from genetic factors when a plant isn’t getting enough carbon through photosynthesis because it has greater need from stress recovery or rapid growth it also makes the plant more susceptible to infections. Especially when the hurd expands to increase the size or the xylem it decreases the healthy pith mass. When the pith gets infected it travels fast and can take a whole plant down in days.
Higher carbon in soils is good, but focusing on maintaining proper respiration will help more. Even if you have higher carbon in your soil increasing the c02 levels the leaves still need to photosynthesize and process it.
@Chicojackson to prevent it make sure you keep your lighting in healthy ranges and always use clean disenfected/sterile shears to take clones. Then after cutting clean the wound and cover it with some grafting wax, grafting paint, grafting tape, or some other sterile wax/glue/paint/tape to keep the wound clean and free of contamination. You also don’t want it exposed to air so clean it and seal it well. Petroleum jelly or coconut oil and saran wrap will work in a pinch.
Also make sure the plant fully heals between cuttings. At least two weeks before you take cuttings again. Give a good feeding after every cutting too.
Try to maintain as much of the solar canopy as you can too by only cutting clones from the bottom of the plant. They don’t contribute much carbon anyway because they don’t get light and have more auxins in them anyway so they’ll root faster than top cuttings.
It’s also a good idea to foliar feed mothers directly after each cutting session.
