Jove's Oak (interpretatio romana for Donar's Oak and therefore sometimes referred to as Thor's Oak) was a sacred tree of the Germanic pagans located near or in the modern town of Fritzlar in Hesse, Germany. According to the 8th century Vita Bonifatii auctore Willibaldi, the Anglo-Saxon missionary Saint Boniface and his retinue cut down the tree earlier the same century. Wood from the oak was then reportedly used to build a church at the site dedicated to Saint Peter. Sacred trees and sacred groves were widely venerated by the Germanic peoples and scholars have linked this oak and others to the world tree in Norse mythology, Yggdrasil.
Willibald's Life of Saint Boniface 
According to Willibald's 8th century Life of Saint Boniface, the felling of the tree occurred during Boniface's life earlier the same century at a location at the time known as Gaesmere, today part of the town of Fritzlar. Although no date is provided, the felling may have occurred more specifically around 723 or 724. Willibald's account is as follows (note that Robinson has translated robor Iobis, "tree of Jove", as "Tree of Jupiter"):
Cum vero Hessorum iam multi, catholica fide subditi ac septiformis spiritus gratia confirmati, manus inspositionem acciperunt, et quidem, nondum animo confortati, intermeratae fidei documenta integre perceipere rennuerunt, alii etiam lignis et fontibus clanculo, alii autem aperte sacrificabant; alii vero aruspicia et divinationes, prestigia atque icantationes occulte, alii quidem manifeste exercebant; alii quippe auguria et auspicia intendebant diversosque sacrificandi ritus incoluerunt; alii etiam, quibus mens sanior inerat, omni abeicta gentilitatis profantione, nihil horum commisserunt. Quorum consultu atque consilio roborem quendam mirae magnitudinis, qui prisco paganorum vocabulo appellatur robor Iobis, in loco qui dicitur Gaesmere, servis Dei secum adstantibus succidere temptavit. Cumque, mentis constantia confortatus, arborem succidisset, — magna quippe aderat copia paganorum, qui et inimicum deorum suorum intra se diligentissime devotabant,—sed ad mdoicum quidem arbore praeciso, confestim immensa roboris moles, divino desuper flatu exagitata, palmitum confracto culmine, corruit et quasi superni nutus solatio in quattuor etiam partes disrupta est, et quattor ingentis magnitudinis aequali longitudine trunci absque fratrum labore adstantium apparuerunt. Quo viso, prios devotantes pagani etiam versa vice benedictionem Domino, pristina abiecta maledictione, credentes reddiderunt. Tunc autem summae sanctitatis antistes, consilio inito cum fratribus, ligneum ex supradictae arboris metallo oratorium construxit eamque in honore sancti Petri apostoli dedicavit.
Now at that time many of the Hessians, brought under the Catholic faith and confirmed by the grave of the sevenfold spirit, received the laying on of hands; others indeed, not yet strengthened in soul, refused to accept in their entirely the lessons of the inviolate faith. Moreover some were wont secretly, some openly to sacrifice to trees and springs; some in secret, others openly practiced inspections of victims and divinations, legerdemain and incantations; some turned their attention to auguries and auspices and various sacrificial rites; while others, with sounder minds, abandoned all the profanations of heathenism, and committed none of these things. With the advice and counsel of these last, the saint attempted, in the place called Gaesmere, while the servants of God stood by his side, to fell a certain oak of extraordinary size, which is called, by an old name of the pagans, the Oak of Jupiter. And when in the strength of his steadfast heart he had cut the lower notch, there was present a great multitude of pagans, who in their souls were earnestly cursing the enemy of their gods. But when the fore side of the tree was notched only a little, suddenly the oak's vast bulk, driven by a blast from above, crashed to the ground, shivering its crown of branches as it fell; and, as if by the gracious compensation of the Most High, it was also burst into four parts, and four trunks of huge size, equal in length, were seen, unwrought by the brethren who stood by. At this sight the pagans who before had cursed now, on the contrary, believed, and blessed the Lord, and put away their former reviling. Then moreover the most holy bishop, after taking counsel with the brethren, built from the timber of the tree wooden oratory, and dedicated it in honor of Saint Peter the apostle.
Boniface's follow-up 
Boniface established a monastery at the site and a bishopric on nearby Büraberg mountain, where the Frankish fortress had been his base during his campaign in northern Hesse. The initial wooden chapel was soon replaced by a stone building and subsequently by a large Romanesque church, today known as the Dom in Fritzlar.
Germanic tree and grove veneration 
Veneration of sacred groves and sacred trees is found throughout the history of the Germanic peoples and were targeted for destruction by Christian missionaries during the Christianization of the Germanic peoples. Ken Dowden notes that behind this great oak dedicated to Donar, the Irminsul (also felled by Christian missionaries in the 8th century), and the Sacred tree at Uppsala (described by Adam of Bremen in the 11th century), stands a mythic prototype of an immense world tree, described in Norse mythology as Yggdrasil.
See also 
- Capitulatio de partibus Saxoniae, a law code imposed by Charlemagne in 785 that prescribes death for Saxon pagans refusing to convert to Christianity
- Massacre of Verden, a massacre of 4,500 captive pagan Saxons ordered by Charlemagne in 782
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- Although several other locations in northern Hesse bear the name Geismar, there is no longer any dispute about the Geismar in question.
- Robinson (1916:63).
- Emerton (2000:xiv).
- Levison (1905:80—82).
- Robinson (1916:62—64).
- Dowden (200:72).
- Dowden, Ken (2000). European Paganism: The Reality of Cult from Antiquity to the Middle Ages. Routledge. ISBN 0415120349
- Emerton, Ephraim (2000). The Letters of Saint Boniface. Columbia University Press. ISBN 0231120923
- Levison, Wilhelmus (1905). Vitae Sancti Bonifatii archiepiscopi moguntini. Hannoverae et Lipsiae.
- Robinson, George W. (trans.) (1916). The Life of Saint Boniface by Willibald. Harvard University Press.