Ingrain is learned by 29 species by level and 18 by egg

Effect, in PokéAPI's words

“Prevents the user from leaving battle. User regains 1/16 of its max HP every turn.”

Who learns it

46 species in all, 8 of 17 games shown

Scarlet and Violet: 30 species

Species	Method	Level
Lurantis	Level up	1
Sunflora	Level up	4
Fomantis	Level up	10
Cacnea	Level up	22
Cacturne	Level up	22
Foongus	Level up	32
Amoonguss	Level up	32
Snover	Level up	35
Abomasnow	Level up	35
Wo-Chien	Level up	35
Phantump	Level up	40
Trevenant	Level up	40
Brute Bonnet	Level up	70
Bulbasaur	Egg
Ivysaur	Egg
Venusaur	Egg
Oddish	Egg
Gloom	Egg
Vileplume	Egg
Bellsprout	Egg
Weepinbell	Egg
Victreebel	Egg
Exeggcute	Egg
Chikorita	Egg
Bayleef	Egg
Meganium	Egg
Bellossom	Egg
Sunkern	Egg
Petilil	Egg
Capsakid	Egg

Brilliant Diamond and Shining Pearl: 19 species

Species	Method	Level
Roserade	Level up	1
Sunkern	Level up, Egg	4
Sunflora	Level up	4
Lileep	Level up	12
Cradily	Level up	12
Carnivine	Level up	21
Cacnea	Level up	22
Cacturne	Level up	22
Snover	Level up	35
Abomasnow	Level up	35
Tangela	Level up	52
Tangrowth	Level up	52
Roselia	Level up	55
Bulbasaur	Egg
Oddish	Egg
Bellsprout	Egg
Exeggcute	Egg
Chikorita	Egg
Corsola	Egg

Sword and Shield: 26 species

Species	Method	Level
Roserade	Level up	1
Maractus	Level up	1
Lurantis	Level up	1
Shiinotic	Level up	1
Morelull	Level up	8
Fomantis	Level up	10
Lileep	Level up	12
Cradily	Level up	12
Ferroseed	Level up	15
Ferrothorn	Level up	15
Xurkitree	Level up	15
Celesteela	Level up	25
Foongus	Level up	32
Amoonguss	Level up	32
Snover	Level up	35
Abomasnow	Level up	35
Phantump	Level up	40
Trevenant	Level up	40
Xerneas	Level up	45
Tangela	Level up	52
Tangrowth	Level up	52
Roselia	Level up	55
Bulbasaur	Egg
Oddish	Egg
Exeggcute	Egg
Petilil	Egg

Ultra Sun and Ultra Moon: 33 species

Species	Method	Level
Tangela	Level up	1
Cradily	Level up	1, 9
Tangrowth	Level up	1
Xerneas	Level up	1
Shiinotic	Level up	1, 22
Celesteela	Level up	1
Sunkern	Level up, Egg	4
Sunflora	Level up	4
Lileep	Level up	9
Phantump	Level up	13
Trevenant	Level up	13
Foongus	Level up	18
Amoonguss	Level up	18
Fomantis	Level up	19
Lurantis	Level up	19
Xurkitree	Level up	19
Carnivine	Level up	21
Cacnea	Level up	22
Cacturne	Level up	22
Morelull	Level up	22
Snover	Level up	31
Abomasnow	Level up	31
Maractus	Level up	33
Roselia	Level up	34
Ferroseed	Level up	35
Ferrothorn	Level up	35
Bulbasaur	Egg
Oddish	Egg
Bellsprout	Egg
Exeggcute	Egg
Chikorita	Egg
Corsola	Egg
Petilil	Egg

Sun and Moon: 33 species

Species	Method	Level
Tangela	Level up	1
Cradily	Level up	1, 9
Tangrowth	Level up	1
Xerneas	Level up	1
Shiinotic	Level up	1, 22
Celesteela	Level up	1
Sunkern	Level up, Egg	4
Sunflora	Level up	4
Lileep	Level up	9
Phantump	Level up	13
Trevenant	Level up	13
Foongus	Level up	18
Amoonguss	Level up	18
Fomantis	Level up	19
Lurantis	Level up	19
Xurkitree	Level up	19
Carnivine	Level up	21
Cacnea	Level up	22
Cacturne	Level up	22
Morelull	Level up	22
Snover	Level up	31
Abomasnow	Level up	31
Maractus	Level up	33
Roselia	Level up	34
Ferroseed	Level up	35
Ferrothorn	Level up	35
Bulbasaur	Egg
Oddish	Egg
Bellsprout	Egg
Exeggcute	Egg
Chikorita	Egg
Corsola	Egg
Petilil	Egg

Omega Ruby and Alpha Sapphire: 27 species

Species	Method	Level
Tangela	Level up	1
Cradily	Level up	1, 9
Tangrowth	Level up	1
Xerneas	Level up	1
Sunkern	Level up, Egg	4
Sunflora	Level up	4
Lileep	Level up	9
Phantump	Level up	13
Trevenant	Level up	13
Foongus	Level up	18
Amoonguss	Level up	18
Carnivine	Level up	21
Cacnea	Level up	22
Cacturne	Level up	22
Snover	Level up	31
Abomasnow	Level up	31
Maractus	Level up	33
Roselia	Level up	34
Ferroseed	Level up	35
Ferrothorn	Level up	35
Bulbasaur	Egg
Oddish	Egg
Bellsprout	Egg
Exeggcute	Egg
Chikorita	Egg
Corsola	Egg
Petilil	Egg

X and Y: 27 species

Species	Method	Level
Tangela	Level up	1
Cradily	Level up	1, 15
Tangrowth	Level up	1
Xerneas	Level up	1
Sunkern	Level up, Egg	4
Sunflora	Level up	4
Phantump	Level up	13
Trevenant	Level up	13
Lileep	Level up	15
Foongus	Level up	18
Amoonguss	Level up	18
Carnivine	Level up	21
Cacnea	Level up	25
Cacturne	Level up	25
Snover	Level up	31
Abomasnow	Level up	31
Maractus	Level up	33
Roselia	Level up	34
Ferroseed	Level up	35
Ferrothorn	Level up	35
Bulbasaur	Egg
Oddish	Egg
Bellsprout	Egg
Exeggcute	Egg
Chikorita	Egg
Corsola	Egg
Petilil	Egg

Black 2 and White 2: 24 species

Species	Method	Level
Tangela	Level up	1
Cradily	Level up	1, 15
Tangrowth	Level up	1
Sunkern	Level up, Egg	4
Sunflora	Level up	4
Lileep	Level up	15
Foongus	Level up	18
Amoonguss	Level up	18
Carnivine	Level up	21
Cacnea	Level up	25
Cacturne	Level up	25
Snover	Level up	31
Abomasnow	Level up	31
Maractus	Level up	33
Roselia	Level up	34
Ferroseed	Level up	35
Ferrothorn	Level up	35
Bulbasaur	Egg
Oddish	Egg
Bellsprout	Egg
Exeggcute	Egg
Chikorita	Egg
Corsola	Egg
Petilil	Egg