Ive got some friends that sank fir christmas trees, they didnt last a year.
the small limbs rotted off and the larger became water logged, they
ended up looking like a short two by four. I'd use concrete blocks
and cheap nylon line from walmart if i was doing christmas trees.
it might be more efficient to use hardwoods, or cedar, plastic is also a
good option. just my opinion.
john b.