The tree-line is the edge of the habitat at which trees can grow. Beyond the tree-line, they are unable to grow as conditions are too bad (wind, cold and /or not enough soil deepness). As for arctic conditions, that happens in low altitude at about 60 to 70 º N latitudes.
For exemple, in Greenland, experimental tree planting in the absence of native trees due to isolation from natural seed sources resulted in few trees surviving; they grow slowly, at Søndre Strømfjord, 67°N. There is even a small forest, Rosevinges forest , near Narsarsuaq:
In 2005, the first timber cut in Greenland was possible! But to the north, only tundra vegetation , at most some brushwoods of mountain birch. So timber remains more precious than gold..
More about Trees in Greenland here.
But where are the most northern trees in the world ? Well, the answer is Siberia . At the Central Siberian Plateau , extreme continental climate means the summer is warm enough to allow tree growth at higher latitudes, extending to 72°30' N in the Khatanga River valley.
Larch growing close to the Arctic tree-line in the Arctic northeast Siberia.
“Tree in a skirt”
This happens because of the winter weather. When it snows, the bottom of the tree is covered up. This blanket of snow is actually very protective, keeping the lower branches safe. The part of the tree that sticks out of the snow is unprotected, so it is buffeted by the winds.
Khatanga River frozen in winter
The Khatanga River Valley is situated in the Taymyr peninsula, an arctic region where Nganasans are one of the native peoples. They have been nomadic hunters, fishers, and herders of reindee. They are the northernmost people of the former Soviet Union.
Nganasan people are not related to inuits in ethnic terms, but they have similar lifestyles, clothing, mythologies...