Where are the most convenient places to farm for wood in Genshin Impact?

I would focus more on finding rarer trees than big areas to swipe thru. That is because compared to normal resources, tree wood respaws every 10 trees you hit (*). So, basically, you need only ten trees to be able to cycle between them as long as you wish.

As for the wood types:

• Pine can be easily found near the adventurer guild in Mondstadt. No need to go to Dragonspine, just go to the small area with trees to the left of the guild. Since there are more than 10 trees, the infinite cycle is possible.

• Bamboo. Could be found near the pool in Liyue... but why should you bother when there is a bamboo forest at the Wuhang Hill teleporter? Again, far more than 10 trees here...

• Fir, Birch and Cedar are plenty around Dawn Winery. Since the birch is mostly found on the plateau above the winery near the Statue of the Seven while the cedar is mostly along the river, just go from one end to the other.

• Sandbearer - many found along the road from the Guili plains to Liyue, so either start there and go south or start from the Liyue Statue of the Seven and go north (notice: north and sud here being up/down on the map. Based on the game text, the real way north is pointing is still up to debate).

• Cuihua - follow this Reddit post. Basically, there is a route in Dadaupa Gorge, with most of the trees in the Meat Tribe and the Eclipse Tribe camps.

Notice: depending on what you consider efficent, the Wispering Woods near Mondstadt could be a good place too. Birches are also easily found around the statue in Starfell Valley.

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(*) Actually, the game only remembers up to ten "trees". This means that as soon as you hit an eleventh tree that is not in that list, the older one will be forgotten and will produce wood again if hit. That means you can just circle nearby trees.