With regard to the time when the mistletoe should be gathered opinions have varied. The Druids gathered it above all on the sixth day of the moon, the ancient Italians apparently on the first day of the moon. In modern times some have preferred the full moon of March and others the waning moon of winter when the sun is in Sagittarius. But the favourite time would seem to be Midsummer Eve or Midsummer Day. We have seen that both in France and Sweden special virtues are ascribed to mistletoe gathered at Midsummer. The rule in Sweden is that mistletoe must be cut on the night of Midsummer Eve when sun and moon stand in the sign of their might. Again, in Wales it was believed that a sprig of mistletoe gathered on St. John's Eve (Midsummer Eve), or at any time before the berries appeared, would induce dreams of omen, both good and bad, if it were placed under the pillow of the sleeper. Thus mistletoe is one of the many plants whose magical or medicinal virtues are believed to culminate with the culmination of the sun on the longest day of the year.
Hence it seems reasonable to conjecture that in the eyes of the Druids, also, who revered the plant so highly, the sacred mistletoe may have acquired a double portion of its mystic qualities at the solstice in June, and that accordingly they may have regularly cut it with solemn ceremony on Midsummer Eve.
Be that as it may, certain it is that the mistletoe, the instrument of Balder's death, has been regularly gathered for the sake of its mystic qualities on Midsummer Eve in Scandinavia, Balder's home. The plant is found commonly growing on pear-trees, oaks, and other trees in thick damp woods throughout the more temperate parts of Sweden. Thus one of the two main incidents of Balder's myth is reproduced in the great midsummer festival of Scandinavia. But the other main incident of the myth, the burning of Balder's body on a pyre, has also its counterpart in the bonfires which still blaze, or blazed till lately, in Denmark, Norway, and Sweden on Midsummer Eve. It does not appear, indeed, that any effigy is burned in these bonfires; but the burning of an effigy is a feature which might easily drop out after its meaning was forgotten. And the name of Balder's balefires (Balder's Balar), by which these midsummer fires were formerly known in Sweden, puts their connexion with Balder beyond the reach of doubt, and makes it probable that in former times either a living representative or an effigy of Balder was annually burned in them. Midsummer was the season sacred to Balder, and the Swedish poet Tegner, in placing the burning of Balder at midsummer, may very well have followed an old tradition that the summer solstice was the time when the good god came to his untimely end.
Thus it has been shown that the leading incidents of the Balder myth have their counterparts in those fire-festivals of our European peasantry which undoubtedly date from a time long prior to the introduction of Christianity.
The pretence of throwing the victim chosen by lot into the Beltane fire, and the similar treatment of the man, the future Green Wolf, at the midsummer bonfire in Normandy, may naturally be interpreted as traces of an older custom of actually burning human beings on these occasions; and the green dress of the Green Wolf, coupled with the leafy envelope of the young fellow who trod out the midsummer fire at Moosheim, seems to hint that the persons who perished at these festivals did so in the character of tree-spirits or deities of vegetation. From all this we may reasonably infer that in the Balder myth on the one hand, and the fire-festivals and custom of gathering mistletoe on the other hand, we have, as it were, the two broken and dissevered halves of an original whole. In other words, we may assume with some degree of probability that the myth of Balder's death was not merely a myth, that is, a description of physical phenomena in imagery borrowed from human life, but that it was at the same time the story which people told to explain why they annually burned a human representative of the god and cut the mistletoe with solemn ceremony. If I am right, the story of Balder's tragic end formed, so to say, the text of the sacred drama which was acted year by year as a magical rite to cause the sun to shine, trees to grow, crops to thrive, and to guard man and beast from the baleful arts of fairies and trolls, of witches and warlocks. The tale belonged, in short, to that class of nature myths which are meant to be supplemented by ritual; here, as so often, myth stood to magic in the relation of theory to practice.
But if the victimsthe human Balderswho died by fire, whether in spring or at midsummer, were put to death as living embodiments of tree-spirits or deities of vegetation, it would seem that Balder himself must have been a tree-spirit or deity of vegetation. It becomes desirable, therefore, to determine, if we can, the particular kind of tree or trees, of which a personal representative was burned at the fire-festivals. For we may be quite sure that it was not as a representative of vegetation in general that the victim suffered death. The idea of vegetation in general is too abstract to be primitive. Most probably the victim at first represented a particular kind of sacred tree. But of all European trees none has such claims as the oak to be considered as pre-eminently the sacred tree of the Aryans. We have seen that its worship is attested for all the great branches of the Aryan stock in Europe; hence we may certainly conclude that the tree was venerated by the Aryans in common before the dispersion, and that their primitive home must have lain in a land which was clothed with forests of oak.