The Art of Grafting
Japanese maples are usually propagated by grafting. Named cultivars do not come true from seed so a branch is cut from the cultivar and grafted onto a Japanese maple rootstock that was grown from seed. This way you will get the exact clone of the cultivar. Also, some Japanese maples will not grow without the use of a more vigorous, seedling-grown root-system. The rootstock of choice is Acer palmatum, the seedling grown Japanese maple, the one that is found in the wild and has been around for millions of years.