Q. Is a Deutzia tree (10-12') have a single trunk or multiple trunks?
Have found very little on-line and nothing about trunks. Mine have 8 or 10 half inch "sticks" coming out of the ground. Had a friend ask if there were different trees or are they like lilacs with multiple growth from the ground?
It's not possible to identify the plant without a sample, however, all of the shrubs that you mentioned are just that, shrubs, not trees. If you look them up on the internet you will see that Mock Orange or Deutzia grow tall and wide. Whatever it is, if you want to keep it, I suggest you dig it out of the border and put it somewhere where it has enough room to grow. Mock orange is an old fashioned plant that has white flowers about an inch wide. Mock orange is a large, rounded shrub, with stiff, straight, ascending branches that arch with age 10-12' high with clusers of 1" flowers in May. Deutzia has smaller leaves, dark green with clusters of small frilly white flowers smetimes, but rarely pink, the plant grows to 4 to 5' in sun with enough space.