Aśoka tree- A kind of Mahāprātihārya (superhuman magnificence of the Tīrthaṅkara (ford-founder)) god-created Atiśaya i.e., supernatural magnificence of the Tīrthaṅkara (ford founder);
the Tīrthaṅkaras use to sit on a throne under the shadow of the Aśoka tree which has a blue aura.
jattha jatthavi ya ṇaṃ arahāṃtā bhagavaṃto ciṭṭhaṃti vā nisīyaṃti vā, tattha tatthavi ya ṇaṃ... asogavarapāyavo abhisaṃjāyai.
(Sama 34.1.11)
asogavarapāyavoṃ jiṇanccattāo bārasaguṇaṃ sakko viuvvati.
(ĀvaCū 1 p.325)