What happens if a sorcerer is hit with Disintegrate while he has turned into a potted plant?

Question

During the last game of D&D 5E I DMed, my party containing a level 5 Wild Magic Sorcerer encountered a Beholder Zombie. During this fight a Wild Magic Surge effect turned him into a potted plant. Fortunately for him the beholder did not get the chance to use its Disintegration Ray on him but I was wondering what would have happened if it did? (Howerver the beholder did land an Enervation Ray that dropped my player unconcious right away)

First of all would he have been able to save against it? The PHB tells us that turning into a potted plant incapacitates him and make him vulnerable to all types of damages but does that mean that he could still move while turned into a plant? On the spot I ruled it as Paralysis not allowing him to move and allowing him to make a Consitution Saving throw against the Enervation Ray but reading back the PHB made me wonder if I made the right decision.

Secondly, if he did get hit by the Disintegration Ray (and went down below 0 hitpoint), would he have been disintegrated or would the potted plant form would have been disintegrated? Since both effect take place when he goes down to 0 hitpoints I don't really know which effect to apply first. Since it would totally sentence the character to permanent death at this level I wouldn't like to make my player reroll a character after literally getting one shotted by an enemy within its capabilities if there is a chance he did not actually die.

Answer 1

A potted plant has 0 movement speed, so while you can move while incapacitated in some instances, you can't move in potted plant form anyways.

This creation from the wild magic surge does not have a creature statistics block associated with it. Due to this, the character is not considered a creature, but rather an object. Yes, plants are alive, yes you are free to adjudicate he is a creature of the plant variety. A potted plant generally lacks mobility. Some fast growing vines and whatever my wife keeps in the kitchen that eats my dishes are the exceptions.

As for what happens with Disintegrate, well nothing is really clear there. It's going to be up to the DM since there's RAI and RAW that directly contradicts in numerous places.

The Disintegrate spell, upon reducing a creature to zero HP, turns the target into ash. We know from clarifications that features that prevent you from hitting zero HP don't prevent this effect like Relentless Endurance. Support for this is from the rules answers in 2016:

If the damage from disintegrate reduces a half-orc to 0 hit points, can Relentless Endurance prevent the orc from turning to ash? If disintegrate reduces you to 0 hit points, you’re killed outright, as you turn to dust. If you’re a half-orc, Relentless Endurance can’t save you.

However, this is countered by the fact that disintegrate does not turn you to ash with polymorph, shapechange or wildshape. This is evidenced here:

Disintegrate during polymorph, shapechange, wildshape

Basically that question has two answers, both correct, about what happens. Sage Advice covers the RAW which means the target is disintegrated and does not revert. RAI from the designer, Crawford, states that the base creature must hit 0 HP, which contradicts the RAW.

Thanks to these layers of confusion with respect to the consistency of disintegrate, you are stuck with only one possible answer:

DM adjudication.

In my games, if you hit zero in any form while getting hit by disintegrate, it bypasses anything except for spells or items specifically designed to block it. That way it retains its lethality.

Answer 2

A potted plant is an object, not a creature. As a magical object but not a creation of magical force, the Sorcerer-in-potted-plant-form is immune to the effects of the Disintegrate spell and (albeit implicitly) also the effects of the Beholder Zombie's Disintegration Ray. No saving throw is necessary; the Ray just doesn't harm him while he's in plant form.

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Some plants are creatures-- indeed, Plant is even a kind of creature!-- but ordinary plants count as objects instead:

Plants in this context are vegetable creatures, not ordinary flora. Most of them are ambulatory, and some are carnivorous. The quintessential plants are the shambling mound and the treant. Fungal creatures such as the gas spore and the myconid also fall into this category

(from the Monster Manual)

and Speak with Plants makes sure to differentiate between ordinary, non-creature, plants and Plant creatures.

Technically, plants may be some non-object, non-creature 3rd category, but that makes dealing with them weird and hard and ruling that regular plants are objects works fine basically all the time; indeed that's the only way I've seen it ruled in Adventurer's League games, for what that's worth.

Sorcerers, specifically, are magical:

Magic is a part of every Sorcerer, suffusing body, mind, and spirit with a latent power that waits to be tapped

(from the Player's Handbook)

Pretty much every bit of description about sorcerers is about how inherently magical they are. In 5e, things aren't magical unless they are a spell, replicate the effects of a spell, or explicitly say they are magical. Sorcerers are explicitly said to be magical more than 14 times in their Player's Handbook description. There is basically nothing else in the game that is as explicitly and consistently called out as magical as sorcerers. Even spellcasting isn't quite as loquaciously tied to magic by name.

A Wild Magic Sorcerer, then, who is an ordinary plant is either a magical object or a magical not-an-object-or-creature. Since the eye ray in question only affects creatures, non-magical objects, and constructions of magical force, such a character is unaffected by said eye ray.