I have received a few brugmansia cuttings but they are linear. Can I expect a Y to form or should I prune it somehow to encourage it?

MonicaRomano, use fertilizer that is 20/20/20 and let them grow. They will 'Y' do not cut as you will have to just wait longer. Once they 'Y' then you can switch to a bloom booster to get them to bloom. Some varieties will only grow as shrubs where others can be trained as trees. Do you know the varieties? Shout if you need more help.