Hey,

I was wondering how many weeks it takes for the plant to grow from the roots instead of the seed aka when do roots take over from the seed ?

greets

I'm not certain, but I think that citrus are cotylendonous (exalbuminous) - they don't have a distinct endosperm when mature, and feed simply from the cotyledons and the root from the moment they germinate. Does someone with more knowledge on this aspect of citrus physiology want to chime in, though?

Citrus is a cotyledon plant. The purpose of the cotyledons is to supply the seedling tree with the needed energy (food) to stay alive until the true leaves develop and take over as the permanent food manufacturing source for the tree. ONE CAUTION: water the young seedlings only in the morning, then set the plants in the sun to quickly dry the surface of the soil. This will go a long way to prevent the seedlings from dying from rhizoctonia (stem rot), the number one killer of young citrus seedlings. - Millet

I'm not sure what "sharpnell" is, but if it is some kind of gravel, stones and etc. you actually have made the problem worse. Adding some type of bulky item to the bottom of a container actually raises the perched water table higher into the container, thus leaving less aeriable room for the root system to grow. - Millet

I use broken container pieces at the bottom.

I do this so that when watering the excess water drips between the pieces, they don't have direct contact with the roots.
I've got kinda high containers so the loss of 2cm at the bottom isn't all that bad I guess.