Weeping Higan cherry aka Prunus subhirtella 'Pendula' is rarely planted from seed, but grown from cuttings.* Snowfountain weeping cherry aka Prunus serrulata x subhirtella 'Snofozam' isn't listed either.* I have a tree germination database and it isn't noted there, though other Prunus are.* You'll need to scroll down at this site.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.