This plant skitters around on a bundle of roots while flailing around its tubers and spitting boiling oil from its flowers.
CR 1; XP 400
N Small Plant
Init +0; Senses low-light vision; Perception +1
AC 12, touch 11, flat-footed 12 (+1 natural, +1 size)
hp 15 (2d8+6)
Fort +6, Ref +0, Will +1
Immune plant traits
Weakness attracted to fire
Speed 20 ft.
Melee 2 slams +2 (1d4)
Ranged oil splash +2 touch (1d4 fire plus 1 splash)
Str 10, Dex 10, Con 16, Int –, Wis 13, Cha 1
Base Atk +1; CMB +0; CMD 10 (can't be tripped)
Environment plains, hills, and ruins
Organization solitary, pair, or patch (3–18)
Treasure edible tubers
Attracted To Fire (Ex) A quirk of their behavior makes dire potato plants instinctively attracted to sources of open fire, which is problematic, as they are quite flammable due to their internal oil supply. A dire potato that suffers fire damage from an open flame starts to burn, suffering additional 1d4 points of fire damage at the start of each of its following turns. All the creatures and objects within 5 feet of a burning dire potato have to succeed a Reflex saving throw (DC 14) at the beginning of its turn or suffer 1d4 points of fire damage as well. A dire potato reduced to 0 hit points by fire damage burrows its tubers within ground where it stands and promptly dies, fertilizing the area with its ashes. If the soil and weather are suitable, 3d6 dire potato saplings grow from its remains within a season or two.
Oil Splash (Ex) A dire potato exudes a boiling hot oil that is easily ignited. A dire potato can squirt a splash of that oil up to 40 feet with no range increment, treating it as a splash weapon dealing 1d4 points of fire damage to creature directly hit, and 1 point of fire damage to creatures within 5 feet of the splash. Creature suffering direct hit becomes susceptible to fire until the oil is washed off or burned away—any fire damage from an open fire source lits the oil causing the creature to burn for 1d4 rounds for 1d4 fire damage per round as per burn special attack.
Dire potatoes were first grown as an attempt to create quickly proliferating, self-maintaining, easily prepared source of nutritious food... And the results fit all those conditions, but they are also quite aggressive and prone to spreading fire.