In the Urban Grower video he hints at removing the bottom branches as lollipopping. I remember trying to Google the term after I watched but I never came up with a grow-site that mentioned it.

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"And though we'd eliminated the threat of the enemy flying planes into buildings, no-one was prepared for terrorists flying two buildings into the sides of planes. No-one was killed but a lot of people were surprised." -Time Trumpet, Episode 3