Wouldn’t grow something from the inside require a very strong force to “move” the already present one? Instead growing from the last “layer” towards the outside would require a lot less force, but perhaps a lot more matter.
Is it even correct that trees grow concentrically?
Now that I think about it, how do plants grow in general? Hahaha
Update: for everyone wondering, yes, my question doesn’t make sense because the i.e. contradicts the question. I don’t want to correct it because I don’t know which part to correct since I was wrong, I thought trees grew new parts inside and pushed older parts outside. So I could correct the i.e. and swap “innemost” with “outermost” but that would mean that people would read a question stating something that is wrong, or I could correct the question and swap “inside” with “outside” but I was wrong and I’m glad I learnt something today. We can all agree that I asked a weird question in a weird way, thank you all for your answers.
Generally in trees you have the xylem in the middle which transports water and minerals from the roots to the rest of the plant. You have the phloem on the outside, it transports photosynthetic products and nutrients to all parts of the plant. The cambium where growth happens sits between them, because there they get easy access to water minerals and nutrients. The xylem is a mix of living and dead cells. The tracheids and vessel elements in the xylem, which are responsible for water transport, are dead at maturity. So it’s probably too hard to move them to grow from the inside out for trees. This whole process of growing thicker is called secondary growth as opposed to primary growth at the tips of stems and roots.
Also if were the other way around and trees would grow from the inside out, you’d have to have vessels going from the leaves to the center of the stems to deliver nutrients, which just complicates everything. And the tree wanted to grow from the inside by 1cm, every “ring” in the xylem would have to grow one centimeter longer in circumference or crack. It’s much easier to just add a layer on the outside. Also having living layer around the tree probably helps it defend itself from pathogens. If all the mostly dead woody stuff was on the outside fungi etc would have an easier time invading, I think.