I'd use trunk.

Bole: Not to be confused with boll as in the boll weevil of the American South.

But you can poll a tree:

Main Entry: 2poll
Date: 14th century
transitive senses
1 a : to cut off or cut short the hair or wool of : CROP, SHEAR b : to cut off or cut short (as wool)
2 a : to cut off or back the top of (as a tree); specifically : POLLARD b : to cut off or cut short the horns of (cattle)


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