The exact meaning of these items is open to interpretation. See Bodhi’s note for two readings; I offer a third. | Āvaṭṭa here might be read as “whirlpool”, “loop”, or “twist”.

Patthara is probably a “spread” of grass, such as was laid down in rituals.

If the ocean is counted as the last item, the total is twelve. Dvādasa can be an ordinal number. | I take the riddle as corresponding with the twelvefold “round” (vaṭṭa) of dependent origination. The “one root” is ignorance; the “two loops” are name-and-form with consciousness (DN 15:22.6); the “three stains” are ignorance, craving, and grasping; the “five spreads” are perhaps the five consequents starting with consciousness; and the “ocean” is transmigration itself.