ON the number of prongs... the normal early on progression from seed to first leaf...and the first 4-5 years is...
seed, then 3 leafer, then perhaps a 2 prong with 3 leaves on each prong, then possibly a 2 prong with 5 leaves on each prong, then 3 prong.. with possibly only 3 leaves on one prong, then 3 prong with 5 leaves on each prong... and that may repeat for a few years... and then eventually get to a 4 prong (first year, possibly 3 leaves on one prong)... then next year 5 leaves on all 4 prongs...
But now exactly how that progresses depends a lot on the conditions...
Condition can be just barley good enough... and the progression thru those stages may go a lot slower... and they may never get to the 4 prong stage (small to medium 3 prongs at best).
Also conditions can be perfect, and the progression thru those stages can go by much faster... first year 3 leafer, 2nd year 3 prong with 5 leaves on each, 3rd year small 4 prong, etc... 4th year large 4 prong.
When they grow it in artificial shade, and cultivated raised beds, applying fertilizers, etc... in just 4 years they can be huge 4 prongs.
I think one of the best possible natural sites for seng to grow in is along a bluff (limestone) bluff that faces almost due east and where the seng plants get lots of morning sun, but no direct evening sun. The soil is loaded with calcium and other minerals, and the light conditions are sweet.
See the picture below...
Those 4 roots top right were found in my normal woods on a north facing hillside, the soil was good but timber heavy, so deep shade. See the long root necks - those were in the 20 year old range, and notice the smallish size... that is about average that I find in my normal woods in heavy timber, deep shade situation. all of those were 10-12" tall average 3 prongs (even though 20 years old or more).
But just down the hollow from where I dug those 4... it runs into a creek and bluff (limestone bluff) 200 ft tall or more, with some soil around that bluff that is just full of rock chips... notice all of those big fat bulby roots, with very short root necks (5-8 years old)... and most of those were BIG stout 4 prongs, or huge 3 prongs, with big berry pods on them.
That is the difference that location can make... soil and light...
Also I think anything over a 4 prong is just where the plant is doing so well, it just has to break out of the norm and grow something extra.
I think that almost always happens in locations where it is just very ideal for growth.
TNHunter