Flat braches on mandarin

[CharlieLoon]

I have a gold nugget which is putting out vigorous new growth with larger leaves and much a flatter/ribbon-like stem/branch. Is this normal? I'm trying to espalier this tree in a formal arrangement, and it's growing stronger than the original branch I had selected for my main leader last summer/fall.

My neighbor's lemon tree has primary branches like this and in my opinion it's rather unsightly and likely structurally weaker. However, my tree won't be growing as tall so the structural concern isn't an issue here. But since the espalier will show off the underlying structure of the tree more and this is the central leader, I'd like the tree to look nice...

It's not a sucker--you can see in the 2nd photo it branches off where all the other branches originate.

First photo gives you an idea of the size of the tree, last photo shows the flatter branch.

Any idea what's going on, and will this self-correct or is it best to nip it in the bud and cut it back and let a new central leader form vs let the old one continue? (The old one hasn't seen new growth in a while)

[kumin]

Initial growth, especially vigorous growth tends to be angular in cross section. Subsequently, during further growth the branches become increasingly rounded to the point of essentially becoming cylindrical. This is a normal process of Citrus branch development.

[Millet]

Looks like normal growth for a young tree.  As Kumin wrote, with good care the tree should grow out just fine.

[CharlieLoon]

Interesting--well that's helpful to know. I couldn't find much info on the more two-dimensional growth in my books or easily online so it had me worried.

[caladri]

Interesting--well that's helpful to know. I couldn't find much info on the more two-dimensional growth in my books or easily online so it had me worried.

Two-dimensional growth would be very impressive I think the term I'm more accustomed to seeing is "angular". There is a more proper term, but I can't remember it. Sometimes knowing what to call a phenomenon and how to think about it determines whether it seems extremely rare or extremely common. In this case, it's absolutely normal.

[CharlieLoon]

Two-dimensional growth would be very impressive I think the term I'm more accustomed to seeing is "angular". There is a more proper term, but I can't remember it. Sometimes knowing what to call a phenomenon and how to think about it determines whether it seems extremely rare or extremely common. In this case, it's absolutely normal.

Haha, I wasn't sure how else to describe it. Kind of like a ribbon I guess? Clearly I don't have a degree in plant science 

Though I am trying to learn!