The spruce was the last of the major species of tree to migrate to Sweden after the last Ice Age, and until about 3 500 years ago the tree was quite rare in Scandinavia. Today however, the tree is the most common in the Swedish flora. Because of this, we often consider the deep, dark forest of spruce trees as being an ancient feature of the Swedish landscape and it is a frequent theme in our representations of folklore and of ancient Norse culture.
The question is how true these representations really are.
For example, many consider the Christmas tree as being a part of some old pagan ritual of decorating the home with a personal sacrificial tree, symbolizing the Norse world tree Yggdrasil, during winter solstice ... but even if Iron Age Scandinavian families did have their own sacrificial trees (which should probably be considered unlikely) not much points to it having been a spruce. An ash tree sounds far more likely, as Yggdrasil was said to be of that particular species (even if there is reason to doubt this assumption). The ash also has a long list of myths tied to it, from the tale of the creation of the first male human to folklorish representations of the ash tree dryad 'Askafroa' ... but it does tend to be rather unimposing during the winter months.
One thing that does speak for the possible importance of spruce trees in Norse Iron Age culture is that the early medieval German bishop Adam of Bremen, from whom we get much of our "understanding" of old Swedish religious practices, describes the temple 'Ubsola' as being situated beside an evergreen tree with far-reaching branches. The evergreen part certainly fits the description of a spruce even if the far-reaching branches is not something you often find among our evergreen friends of the spruce persuasion. As Adam has been somewhat discounted as a reliable source, one should probably be wary of jumping to any conclusions just from reading his account, however.
Oh ... and by the way ... the indoor Christmas tree is in all likelyhood an early modern invention imported from Germany during the 18th century ... and whole forests of spruce were probably still somewhat uncommon during much of the Iron Age.