Pls stop scraping at it. It's some kind of hort. paint or sealant used when they cut back that branch. Note that it's only on the branches whose tops have been cut off.

I've seen large, Mings & different kinds of Aralias have had this done. Not sure why, But I don't think it's good to scrape off & may cause damage if you keep doing it.

Untrue that these plants don't care for much water, but they need fast draining mix including a fair amount of Perlite. In fact, I tend to grow them on humidity trays to keep some moisture around them. They are quite sensitive to soggy soil & being moved around, both can result in leaf drop.

Have you had experience growing other plants? This isn't really one for a beginner (if you are); its watering can be quite tricky. Search around here for how to use a dowel or chopstick to check for moisture.

Thanks for the reply! Fortunately I wasn’t scratching it all off, I just scratched it a little once just to see what it was. I don’t know who cut the trunks, maybe the flower shop where I bought it from? Does this mean that it won’t grow any higher than this or it’ll keep growing?

As for the wattering, I am actually a beginner, I didn’t know it was that hard of a plant to keep, I repoted it with a light soil for cactus, it contains peat moss, perlite, fertilizer and some sand to add weight... I also put about 1 1/2" of river rocks on the bottom to enhance drainage. I will search for a way to have a good "reading" of its humidity... Any other advice? I love this tree and want to keep it healthy and see it grow very tall :)