We have a lot of inkberries (cultivar 'Shamrock') that we started as slips from Musser about 5 years ago. The ones in good soil are now about 2 ft tall, 1 wide.

There are some growing nearby that are about 5 ft tall, 3-4 wide, probably about 10 years old.

Hope you get more helpful replies! Have you looked in the Shrubs forum?

Thanks for your input, lakedweller. I checked in the Shrubs forum and found some information that was useful. You said you started "slips". How did you do that? I'm assuming you cut some stems and rooted them in water. Is that right? I'd like to try that if we need more inkberry.

We decided to use the cultivar 'Nigra' and saw some Shamrock' at the nursery and liked them too. We're planting them in a real rural setting in a wet area so we wanted the rangey look of 'Nigra' rather than the more sophisticated look of 'Shamrock'. We'll plant Virginia Sweetspire with the Inkberry and think they will look nice together. Thanks for your help.

RE: slips--I was being inaccurate. The inkberries were 'seedlings' mail-ordered from Musser Forests. As far as I remember, they looked like 6-inch rooted twigs. The big ones near us are growing on the bank of a canal, whereas most of ours lead a hard life on a steep slope competing with large trees.
I did start some sweetspire from cuttings, but it layers easily, too.
You might find this book interesting:
Growing and propagating showy native woody plants, by Bir, Richard E. (not the better known Dirr). I get it at the library.