Why are plants immune to poison?

[Bohandas]

Why are plant creatures immune to poison? This doesn't make any sense to me. Agent Orange and Roundup were both on the market even way back when Gygax and Arneson published the first edition. What gives?

[Remuko]

probably because of the human-centric design of the game. plants are immune because they were only thinking of human poisons.

[Mechalich]

Modern herbicides are very modern, most weren't developed until WWII and they require advanced chemistry to produce. Unlike the sort of animal-killing poisons available to pre-industrial D&D societies, in D&D terms they're essentially a magical effect. There probably should be a spell that slowly kills plants over a wide area, but since such a thing isn't exactly useful for dungeon crawls, it's not really placed into the game.

[Psyren]

They're "immune to poison" because pretty much everything that is considered "poison" in D&D doesn't affect them.

That doesn't mean there are no substances that can harm them, rather it means those substances aren't categorized as "poisons." Pathfinder for example has alchemical substances like Defoliant (https://www.d20pfsrd.com/equipmenT/goods-and-services/herbs-oils-other-substances/#Defoliant) if you want to kill plants.

[Tzardok]

Most of the poisons in the game are specced against animals and other things that have, y'know, muscles, sinews, blood circulation and so on. It's like if a flower were bitten by a spider; the muscle-paralyzing toxin wouldn't know where to start.

But plants are called out as one of the groups that you can invent worklable poisons for (I think it's under poison immunity in the MM) in contrast to undead against whom you can't do that.

[Psyren]

But plants are called out as one of the groups that you can invent worklable poisons for (I think it's under poison immunity in the MM) in contrast to undead against whom you can't do that.

And then they promptly invented positoxins to fill that niche :smalltongue:

[Darg]

There probably should be a spell that slowly kills plants over a wide area, but since such a thing isn't exactly useful for dungeon crawls, it's not really placed into the game.

Control weather and fimbulwinter can do that. Of course it's just a byproduct, but it could work if you have time and don't care about life in the area.

[Tzardok]

Control weather and fimbulwinter can do that. Of course it's just a byproduct, but it could work if you have time and don't care about life in the area.

Shouldn't Horrid Wilting do that? I mean, sure, by RAW it only affects creatures and non-mobile trees are objects, but I would rule that it kills all plants in the area.

[Thurbane]

Jungelrazer (SC) and Despoil (BoVD) kind of do this, but not so much slowly over time.

Despoil means the area can never support plant life again, requiring multiple castings of Wish or Miracle to undo.

Junglerazer specifically notes that "plants and plant creatures" are affected.

[ShurikVch]

Speaking of BoVD: there is the Evil Weather (Plague of Nettles)

Also: Blighter's Deforestation

Finally, "Defiler magic" from the Dark Sun:

From the mightiest tree to the tiniestlichen, every bit of nonsentient life in the immediate vicinity of the defiling spellcaster is utterly destroyed, turned to a fine ash. The land is sterile and won't sustain life for decades or centuries afterward.
The radius of this destructive effect depends on two factors: the amount of vegetation around and the number of defiler points earned when the spell was cast. See the Range of the Defilement sidebar.
If you cast a spell from within a recently defiled area (often because you defiled it the previous round), add the radius of the previous defilement to half the new radius to figure out how much land is defiled. Calculate the new radius as if the old vegetation were still there. "Half the radius" sounds like a smaller area, but it actually defiles more square footage on a per-spell basis than the original spell. Successive defilements from the same place deal disproportionate damage to Athas; you’re effectively attacking an open wound.

[Thurbane]

I seem to remember a lava or magma based spell, which stated plants don't grow back for X number of years, but I'm struggling to find it now...

[Biggus]

Most of the poisons in the game are specced against animals and other things that have, y'know, muscles, sinews, blood circulation and so on. It's like if a flower were bitten by a spider; the muscle-paralyzing toxin wouldn't know where to start.

But plants are called out as one of the groups that you can invent worklable poisons for (I think it's under poison immunity in the MM) in contrast to undead against whom you can't do that.

This. The relevant section is:



Poison Immunities

Creatures with natural poison attacks are immune to their own poison. Nonliving creatures (constructs and undead) and creatures without metabolisms (such as elementals) are always immune to poison. Oozes, plants, and certain kinds of outsiders are also immune to poison, although conceivably special poisons could be concocted specifically to harm them.

https://www.d20srd.org/srd/specialAbilities.htm#poison

[Smegskull]

They don't have a circleatory system so though there are poisons that work on plants the D&D poison system of effect at damage and secondary 1 minute later doesn't apply.

So it's not that plants are immune to poisoning but rather they are immune to the mechanic named poison.

[ShurikVch]

Defoliator (Arms and Equipment Guide): 1 lb. splash weapon which does 2d4 damage on direct hit to Plant creatures, and instantly kills normal plants of Medium size or smaller; splash does 1 damage to Plant creatures, and instantly kills normal plants of smaller than Medium size; also, it damages wooden objects (although hardness still applies); 20 gp; DC 20 to create