How do you get the limbs to grow down into the umbrella shape? I picked some small trees from our downtown area about 18 months ago, (the bigger ones were umbrella shaped). I thought they grew like that naturally with a little trimming. My sister said they need to be grafted, but I'm not sure how that is done. I have about 6 trees that are now close to 4 ft tall and don't know what to do with them.
Umbrella Shaped Trees
I could give better advice if I knew what kind of tree you're talking about, but I'll try to make some general comments. Some trees grow into an umbrella, or weeping shape quite naturally, others require careful pruning and shaping. You can gradually develop this shape by pruning back branches to the smaller shoots that are angled down, so that the small shoot becomes the end of the branch, and continues to grow in that direction.
Pruning and grafting are two different things. This article on grafting may answer some of your questions: https://www.gardeningknowhow.com/ornamental/trees/tgen/grafting-trees-what-is-tree-grafting.htm