Wow. I'm so glad to see these. I've got some spirea's in the yard that I layered off some of the lower branches of just for fun. One of the new spirea's I got has a single trunk about as big around as a pencil right now but I think with the right growing and pruning methods it should be able to stay single trunked.

You said two years ago. That's some good progress. Did you do much along the lines of branch selection and wiring in that time?

I'd love to see your spirea's silouetted without their leaves. Do you have any pictures of them without their leaves?

You mentioned you bought these from a nursery. Were they purpose grown for bonsai? Looks like a good selection you chose.

They are from local nurseries, not grown for bonsai, the second one was cut down initially just this spring. Both trees are still pretty raw, I think in four or five years they might start to look nice. I'll show pics later when the leaves have fallen. Thanks for your interest.

This looks like the classic Bridal Wreath Spirea, S.arguta.

Here is a link that might be useful: Bridal Wreath