I have already argued elsewhere that I am firmly convinced that South Asian philosophers upheld that plants are non-sentient, probably against the common belief in their sentience.
A further evidence had escaped my attention until now, namely Pūrva Mīmāṃsā Sūtra 1.2.35, where an opponent says that Vedic mantras are meaningless, since they address acetana ‘insentient’ beings. The example that follows in the commentaries departing from Śabara’s one is that of a mantra addressing herbs, oṣadhis.
The siddhāntin replies in sūtra 46, and defends the meaningfulness of mantras, but still agrees with the assumption that herbs are not sentient. The same point is repeated throughout Mīmāṃsā and also in the Viśiṣṭādvaita Vedānta commentary by Veṅkaṭanātha on the same sūtra. This adds other examples of mantras addressing insentient beings, further clarifying that the opponent really groups together herbs and stones or other inorganic elements.
The sentience of plants is one of the topics I keep on thinking of. You can read my last post about it here.