He means conserve resources, specifically as opposed to lopping branches. Which is true.
No one is trying to make the trunk thicker, but by conserving resources in any manner, you will build more trunk, regardless of how fast or where.
Sorce
Not exactly. Trees put on wood to support themselves. If there’s no apical growth, the trees don’t have any reason to fatten the trunk.
You want a fatter trunk? Let a shoot from the apex grow unimpaired. There’s a complex system of hormones that all work together that directs the tree to produce (or not produce) trunk mass. But, the key factor is strong apical growth. That strong growth produces the hormone auxin. Auxin has a lot of effects on the tree. And the flow of auxin (or lack thereof) is a signal to build wood (or not). Pinching the strong growth on the apex removes the source, the auxin factory. No auxin (or reduced levels of auxin) tells the tree it’s NOT growing taller. Therefore, no need to make a stronger trunk to support itself.
On the other hand, if you do want a thicker trunk, let the apex grow! There will be a strong auxin source, and strong auxin flow. The tree will build more pathways to move sugars down, and water up. Those pathways are the phloem and xylem that eventually become “wood”. Here’s a picture of the process at Telperion Farms:
Notice, they are letting a sacrifice branch grow straight up tall. But keeping small short branches down low. Those low branches aren’t making the trunk fat, it’s the tall sacrifice.
Have you ever heard that once you put a tree into a bonsai pot the trunk stops getting fatter? It’s mostly true. It will get a bit fatter each year, but not nearly as much as if grown in the ground or even a larger container. Bonsai pots restrict the growth of the roots. And we tend to trim and style the trees which removes the auxin.
Here is a picture of one of my forests that I wanted to fatten the trunk on one of the trees:
I let a shoot grow on a branch up in the apex unchecked. I pinched all the others. Where I pinched, I got a bunch of little secondary branches. Increased the ramification. The sacrifice branch, if you notice, is rather sparse. I didn’t remove any leaves or anything, it just grew long. Put on wood. Compare the size of the wood on it to all the other branches you can see. By pinching, those branches stayed thin. Unpinched, it put on wood.
Leaves DO NOT produce wood! AUXIN or the flow of auxin, is what puts wood on trees. That sacrifice branch has few leaves. But it has lots of wood. The branches below have lots of leaves, but little wood!
I have seen lots and lots of posts that make the claim that having lots of foliage is how to make the branch or trunk thicker. Sorry, it’s just not so. Having lots of GROWTH is what makes branches and trunks thicker.
