Jeremeyi, the original shoot should grow taller. In case it starts to dry out, and sometimes this happens, then you will need to select another shoot to use as the main trunk. Know that some brugs grow faster than others. You don't say how long your rooted cuttings are, but if they are small, I would hold back on pruning until the plant is well established and a bit taller. Then I would just prune any aggressive shoots from the sides. Hope the experts respond on what they do to make a standard.

Sometimes the shoots grow straighter and taller, and are better looking than the mother. If you want flowers, don't cut below the first Y on the trunk. If you like the shape of the mother, do as already said and prune off the shoots.

Yes, the original shoot will grow taller and thicker in dimension. If the original cutting had growth at the top, you can trim off lower branches until the original shoot is almost 1/2 the length (tall) you desire. I'm interested in seed or cutting exchanges, I have a super blooming yellow brugmansia. I'm looking for pink or any color of "Double Blooming" brugmansia. If you're interested, my email address is angletrumpet4sale@aol.com.