This bur oak acorn that I planted in the fall has started to sprout over the past few days and I'm wondering if it needs to be buried a little deeper in the soil. It hadn't grown at all in like two months, with just the dark green part sticking out of the acorn shell. As you can see from the pictures, it is going through a growth spurt.
I think that brown part coming out of the soil was covered up by the acorn shell until I repotted it about a week ago. I'm not sure if it is stem or root. I haven't found any good reference pictures so I thought I'd ask the good folks on stackexchange for some help. Thank you!

