I'm also very new at this but I know what lining out is.
When you plant all of one cross in a pot, you will probably want to line them out or separate them and make a row of them in the garden.
Kind of like with my dayliles
I have a whole cross in a cup and I will want to line them out because they will all be different.
I have about 15 Iris seed pods! (Out of hundreds of crosses)
