Hello Heather,
I have looked at my actual piece and I do not have any stems to the leaves.? the leaves are big enough to meet the main stem.? if you ant to do the stem them yes it should be in coral knots.? But my advice would be to do what looks good.? Do not worry too much if it is not exactly like the drawing.? For instance if a line is not the shape you want them make it what you want.? if the motif is not quite the shape you like then do what you like.? Remember I am a terrible drawer so sometimes my shapes are not quite right or even. ?
Also remember that Schwalm embroidery was a peasant embroidery and not always perfect.? We tend to be too precise sometimes and sometimes the beauty is in the quirkiness.? So do not worry too much about it being perfect but making it look as good as you can.
Hope this helps.
Regards,
Barbara