Herbology Kit Guide

A Herbology Kit is used to grow plants / ingredients outside of class. It's an optional activity that boost skills and may grant rare ingredients, which otherwise can't be found or bought. Once you have it, it's permanent. You're free to use it whenever your character has morning or afternoon free time.

There's no limit to how many characters can have a Herbology Kit or be working towards it. However, to keep space limits and reward earning fair -- only 1 character per member can grow plants at a time. This way your characters can take turns if you want to use more than one of them for this feature.
Cannot be done at night or during meals. Complete the following tasks:

1) Visit Hagrid and ask him if he has a spare pot you could use to grow your own plants. He'll get one and fill it with soil. This is your free starter pot; once you have the kit, pots can be bought from the WizShop.

2) Take your pot to Professor Sprout's Office, which is located in the Entrance Hall location. If she's not there, try the Staff Room or see if she's present in a Gardening thread. Once you've found her, explain that you'd like to grow your own plants.

3) Sprout will ask you to prove yourself by learning the Water-Making Charm. She'll teach it to you and award 8 house points for its completion. You'll receive free seeds, earmuffs, and permission to use the Student Greenhouse. Additional seeds are bought from the WizShop. Whoever uses the Student Greenhouse (for planting / harvesting) first each morning or afternoon must make a gardening thread. Its title should be in the following format: "#3 morning - Gardening". When you're finished, it stays for anyone else to use during that time slot. Students are free to come and go, even if in the same post. 
1) X ingredients can be grown by anyone with a Herbology Kit. XX ingredients require a Herbology skill of level 1 or higher, and XXX ingredients level 2 or higher. They take 1 morning / afternoon time slot to grow; if you plant seeds in the afternoon, they'll be ready the next morning -- and vice versa. The Greenhouse is locked at night. You cannot have more than 5 seeds growing at the same time.

2) Check the "Growth Progress" thread to see which slots are available. In the gardening thread, RP your character coming in and choosing their slot to work at. You'll need an empty pot and some seeds, which are 1-use items. Place the seeds in soil and water them with the Water-Marking Charm. Your pot will be added to the Growth Progress to can keep track of it. No further action is required until it's grown.

3) When grown, its image will change from a pot to the plant / ingredient. Use the gardening thread to RP harvesting the plant. Modding is required to determine the process, as some plants are dangerous or require extra work / tasks. Plants don't wilt or rot; remaining in the greenhouse until harvested or the Hogwarts year concludes.X Ingredient ~ 1 house point. 40 Herbology experience.
XX Ingredient ~ 2 house points. 60 Herbology experience.
XXX Ingredient ~ 4 house points. 90 Herbology experience.

Additional experience may be applied to certain outcomes or plant handling.If you own an Advanced Pot, during each harvesting session (regardless of which pot/s are in use) of 3 or more plants, you may find a Mystery Seed. This strange item can only be planted in an Advanced or Deluxe Pot. There are 4 possible plants it may grow, which are chosen at random.

The growth time and harvesting progress are the same as any ingredient. However, no item is received for harvesting a Mystery Plant; as these plants are unknown and with no obvious use, they simply add to your character's experience. Perhaps over time, their mysteries may be solved?

Mystery Plant A ~ 80 Potions experience.
Mystery Plant B ~ 110 Potions experience.
Mystery Plant C ~ 70 Curses experience.
Mystery Plant D ~ 100 Defence experience.

Each harvest of a Mystery Plant also earns 1 house point, and 40 Herbology experience.Extra items (such as Protective Gloves, and Earmuffs) help in harvesting certain rare ingredients or when managing plants. These are often used interchangeably with Potions and Herbology kits as they have similar tasks and benefits. For example, gloves may mean fewer trips to the Hospital Wing. 

Fertiliser Potion: reduces growth time for any plant by 1 time slot -- with ordinary seeds, this is an instant-growth advantage. Be sure to pour in the potion before watering the seeds. However, you won't receive house points as a harvest reward.

Advanced Pot: a rare but unbreakable alternative to the standard pots. Cannot be bought, as it's only given as a special reward for certain events or contests. Each character may have up to 3, which are infinitely reusable. Owning one also enables you to find Mystery Seeds.

Deluxe Pot: only for characters who don't have an Advanced Pot. A Mystery Seed is provided with this 1-use pot. It's a temporary solution / way of accessing the feature while working towards getting your own Advanced Pot and finding the Mystery Seeds naturally. It can be costly over time, but is an option if needed.