Aelian, Historical Miscellany
So great was superstition among the Athenians that, if someone cut down a small holm-oak from a hero's shrine, they put him to death.
Ὅτι τοσοῦτον ἦν Ἀθηναίοις δεισιδαιμονίας, εἴ τις πρινίδιον ἐξέκοψεν ἐξ ἡρῴου, ἀπέκτεινον αὐτόν.
For protection of trees in a hero's shrine, see also Pausanias 2.28.6-7 (tr. W.H.S. Jones):
Deiphontes and his children – for before this children had been born to him, Antimenes, Xanthippus, and Argeus, and a daughter, Orsobia, who, they say, afterwards married Pamphylus, son of Aegimius – took up the dead body of Hyrnetho and carried it to this place, which in course of time was named Hyrnethium.
They built for her a hero-shrine, and bestowed upon her various honors; in particular, the custom was established that nobody should carry home, or use for any purpose, the pieces that break off the olive trees, or any other trees, that grow there; these are left there on the spot to be sacred to Hyrnetho.
Δηιφόντης δὲ σὺν τοῖς παισίνἐγεγόνεσαν γὰρ καὶ παῖδες αὐτῷ πρότερον ἔτι υἱοὶ μὲν Ἀντιμένης καὶ Ξάνθιππός τε καὶ Ἀργεῖος, θυγάτηρ δὲ Ὀρσοβία: ταύτην Πάμφυλον τὸν Αἰγιμίου λέγουσιν ὕστερον γῆμαι:τότε δὲ ἀναλαβόντες τὸν νεκρὸν τῆς Ὑρνηθοῦς κομίζουσιν ἐς τοῦτο τὸ χωρίον τὸ ἀνὰ χρόνον Ὑρνήθιον κληθέν.
καί οἱ ποιήσαντες ἡρῷον τιμὰς καὶ ἄλλας δεδώκασι καὶ ἐπὶ τοῖς πεφυκόσιν ἐλαίοις, καὶ εἰ δή τι ἄλλο δένδρον ἔσω, καθέστηκε νόμος τὰ θραυόμενα μηδένα ἐς οἶκον φέρεσθαι μηδὲ χρᾶσθαί σφισιν ἐς μηδέν, κατὰ χώραν δ' αὐτοῦ λείπουσιν ἱερὰ εἶναι τῆς Ὑρνηθοῦς.