On Friday I brewed up some tree beer using Leyland Cypress boughs in the strike and sparge water as well as in the mash vessel. OG was ~1.050 and I split the boil to brew up a saison and a pale ale with galaxy and sultana (denali) hops. The saison is fermenting with a wild yeast culture I captured from my neighbor's raw honey and the pale ale has Framgarden kveik. They're both fermenting at 87°F/30.5°C
The Leyland Cypress gives the beer a pleasant evergreen/christmas tree flavor that's a bit citrusy and not too overwhelming. I've brewed with this tree a number of times and thoroughly researched it so I'm fully confident that it is not toxic. I don't measure the amount of tree I put in the beer, basically just put branches into the kettle until it's annoying to try to add another one.
Pine can be pretty intense (if it actually was a pine tree). Spruce can also get pretty resiny if you're using mature branches, this is why most people use the new growth tips. I've yet to try Noble Fir, which is what we typically get for our Christmas tree, maybe one of these years.