The following is a list of known ingredients in the game--though most are used to unknown ends. Special note: growing a "large plant" requires a "large pot" potting station.
Ashwinder Eggs
Type: Fauna
Used in the creation of edurus potions.
Dark Flatcap
Type: Mushroom
Available at the Magic Neep.
Dittany
Type: Plant
Used in the creation of wiggenweld potions. Was an ingredient being grown in the Room of Requirement during the gameplay reveal trailer.
Fertilizer
Used to accellerate the growth-rate of plants, though some fertilizers can only be used with certain plants.
Fluxweed
Type: Plant
Available at the Magic Neep.
Horklump Juice
Type: Processed Ingredient
It is a bottle of fluid--presumably from a horklump--used in the creation of wiggenweld potions. Shown being poured into an unknown potion during the gameplay reveal trailer in potions class. This fluid comes from a specific species of jumping mushroom found throughout the magic world.
Knotgrass
Type: Plant
Available at the Magic Neep.
Lacewing Flies
Type: Fauna
According to Natsai Onai, when stewed these are an ingredient used in potion-making. There is a great spot to farm them just outside the school heading toward the Forbidden Forest.
Leech Juice
Type: Fauna
Throughout the world, you will find leeches on the ground near ponds, rivers, lakes, and other water-filled areas. Simply walk up to the leech and interact with it to extract the juice. It is unknown at this time which potion(s) use this ingredient.
Mallowsweet
Type: Herb
Shown being grown in the Room of Requirement during the gameplay reveal trailer (to the left of the Dittany). While it is unknown if they are used as ingredients in potions, mallowsweet is the trigger that activates Merlin Trial puzzles. It is highly recommended to carry extras in case you fail one of the trials.
Mandrake
Type: Plant
Baseline Time to Grow: 25 minutes
While it has been confirmed that mandrakes can be deployed on the battlefield to incapacitate enemies, these could also possibly serve as an ingredient. Shown being grown in the Room of Requirement during the gameplay reveal trailer and in Herbology class during the launch trailer.
Mongrel Fur
Type: Fauna
Used in the creation of edurus potions. Found sometimes when you murder a dog.
Venomous Tentacula Leaves
Type: Large Plant
Baseline Time to Grow: 25 minutes
Highly-venomous yet valuable potion ingredient. Confirmed as a growable item in the Room of Requirement
Seeds
There are only some plants that can be grown from seed:
- Dark Flatcap Seeds
- Dittany Seeds
- Fluxweed Seeds
- Knotgrass Seeds