My attention was drawn to a post at about.com by a certain N. S. Gill here:
On This Day in Ancient History: Entrance of the Tree
Monday March 22, 2010
The ancient Roman festival of the Magna Mater (Great Mother Cybele) included the Arbor intrat (entrance of the tree) on March 22. An imported goddess from Phrygia, Magna Mater was installed in Rome in 204 (at the time of Hannibal) where she grew in importance. A pine tree was made to represent the dead Attis for the day of the entrance of the tree. The Dies sanguinis “Day of Blood” followed on the 24th of March and the “Cleansing” on the 27th. See
“The Cannophori and the March Festival of Magna Mater,” by Duncan Fishwick. Transactions and Proceedings of the American Philological Association, Vol. 97. (1966), pp. 193-202.
Now I am a sceptical soul. I do wonder, therefore, what ancient evidence stands behind all these statements. Unfortunately I don’t have a copy of the Fishwick article, although it is in JSTOR here — anyone care to send me a copy? — but I have a feeling that the answer is “very little”. Indeed some of this may be inferred from rather than stated by ancient sources.
I looked into Attis and the sources some time ago, although I never compiled a final version. My working notes are here. These tell me that a statement in John the Lydian, De Mensibus IV. 41 reads:
On day 11, the kalends of April, a pine tree is carried into the Palatine by the tree-bearers. But the emperor Claudius instituted these these ferias, a man of such justice in judgement that…
John the Lydian’s work needs translation. It always has interesting things to tell us about Roman religion and festivals. But moving on, Arnobius, Adversus Paganos book V tells us:
… how can you assert the falsehood of this story, when the very rites which you celebrate throughout the year testify that you believe these things to be true, and consider them perfectly trustworthy?
For what is the meaning of that pine which on fixed days you always bring into the sanctuary of the mother of the gods? Is it not in imitation of that tree, beneath which the raging and ill-fated youth laid hands upon himself, and which the parent of the gods consecrated to relieve her sorrow?
What mean the fleeces of wool with which you bind and surround the trunk of the tree? Is it not to recall the wools with which Ia covered the dying youth, and thought that she could procure some warmth for his limbs fast stiffening with cold? What mean the branches of the tree girt round and decked with wreaths of violets? Do they not mark this, how the Mother adorned with early flowers the pine which indicates and bears witness to the sad mishap?
What mean the Galli with dishevelled hair beating their breasts with their palms? Do they not recall to memory those lamentations with which the tower-bearing Mother, along with the weeping Acdestis, wailing aloud, followed the boy? What means the abstinence from eating bread which you have named castus? Is it not in imitation of the time when the goddess abstained from Ceres’ fruit in her vehement sorrow?
17. Or if the things which we say are not so declare, say yourselves-those effeminate and delicate men whom we see among you in the sacred rites of this deity-what business, what care, what concern have they there; and why do they like mourners wound their arms and breasts, and act as those dolefully circumstanced?
What mean the wreaths, what the violets, what the swathings, the coverings of soft wools? Why, finally, is the very pine, but a little before swaying to and fro among the shrubs, an utterly inert log, set up in the temple of the Mother of the gods next, like some propitious and very venerable deity?
That pine which is regularly born into the sanctuary of the Great Mother, is it not in imitation of that tree beneath which Attis mutilated and unmanned himself, which also, they relate, the goddess consecrated to relieve her grief?
I don’t see a reference here to the tree representing Attis; rather it represents the tree under which that luckless boyfriend of Cybele castrated himself.
Arnobius is clearly well informed. But these are the two references to pine trees in the sources I could find.
What about calendrical material? I always look at the calendar in the Chronography of 354. And sure enough, on the 11th day before the Kalends of April we find ARBOR INTRAT. A couple of days later, SANGUEM. And the day after, HILARIA.
When Mommsen edited the calendar, in Inscriptiones Latinae Antiquissimae, Berlin (1893) pp.256-278, he added learned notes. I wish I had a copy of these!
A google search on “arbor intrat” reveals a miserable collection of sites repeating hearsay, often referencing the Fishwick article.