I never go by how many prongs it has, I use to until I was digging a patch one day and noticed at the top of the patch was a couple two prongs so I figured well since those are at the top maybe they produced this patch. I checked them to see how big they were and it was the two biggest and the oldest out of the entire patch. I dont know why but some plants never change they stay 2, 3 or 4 prongs. It just depends on the soil, iv'e noticed when hunting in beech trees alot of the 2 prongs will be 20 years or older. Which alot of them will be smaller roots but if they are that old and still small their not going to get much bigger. Thats about the only time I check 2 prongs when im hunting in beech trees or if I find some growing in a logging road. I found a 2 prong in a logging road one day and the stem on it was real dark and fat so to my surprise that root ended up weighing just over a half ounce. Thats why I always check some of them, just because its a 2 prong doesnt mean its going to be small or to young to dig. Thats what I love about hunting ginseng you always get surprised.