Multiattack

The vesiculosa uses Entrap 4 times, and uses Reel and Engulf once each. It loses one Entrap attack for each rootlet swarm that's been destroyed.

Entrap

The vesiculosa targets a Large or smaller creature within 5 feet of one of its rootlet swarms. The target takes 10 (4d4) piercing damage and is grappled (escape DC 15), or takes half damage and isn't grappled if it makes a successful DC 17 Dexterity saving throw. Until the grapple ends, the target is restrained, it has disadvantage on Strength checks and Strength saving throws, and that rootlet swarm can't entrap another target.

Reel

Each rootlet swarm that has a creature grappled moves up to 20 feet toward the vesiculosa's main body. Rootlets wander up to 100 feet from the main body.

Engulf

The vesiculosa engulfs all restrained or unconscious creatures within 5 feet of its main body (up to 2 Large, 4 Medium or 8 Small creatures). An engulfed creature is restrained, has total cover against attacks and other effects outside the vesiculosa, and takes 21 (6d6) acid damage at the start of each of the vesiculosa's turns. When the vesiculosa moves, the engulfed creature moves with it. An engulfed creature can try to escape by using an action to make a DC 15 Strength check. On a success, the creature escapes and enters a space of its choice within 5 feet of the vesiculosa's main body.