this is what me n my bb [5 year old daughter] made last year, not an arbor but i do plant to make one this year.
i used 2x4's for the fram n nailed lattice on it, its very strong. its a 5x5 fram bb calls it bb's house lol

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How are you looking to train an Angel Trumpet (Brugmansia) on an arbor? It's a tree like perennial. In areas with no cold temps it really is a tree and in temperate climates it usually reaches about 8-10' during the growing season. In zones 7b -9 it will die back and return in the spring. In colder zones it's normally brought inside and allowed to go dormant over the winter.
Karyn