Matsya Purana — Genealogy of Kaśyapa: Ādityas
तृणवृक्षलतागुल्मम् इरा सर्वम् अजीजनत् विश्वा तु यक्षरक्षांसि जनयामास कोटिशः //
tṛṇavṛkṣalatāgulmam irā sarvam ajījanat viśvā tu yakṣarakṣāṃsi janayāmāsa koṭiśaḥ //
Irā brought forth all grasses, trees, creepers, and shrubs; and Viśvā, in countless numbers, generated the Yakṣas and the Rākṣasas.
It describes sarga (emanation/creation): vegetation is produced first as a foundational life-supporting category, and then specific classes of beings like Yakṣas and Rākṣasas are generated in vast numbers.
By grounding society in a created order—plants and protective/hostile beings—this verse implicitly supports dharma: householders depend on vegetation for sustenance and ritual offerings, while kings are tasked with protecting people from harmful forces symbolized by rākṣasas and maintaining order in the realm.
No direct Vāstu or temple rule is stated, but the mention of vegetation aligns with ritual ecology: grasses, trees, and creepers supply key materials (kuśa, wood, leaves) used in yajña, consecrations, and sacred-space preparation discussed elsewhere in the Matsya Purana.