AppGamer Answered:
Complete the main quest 12, Herbology Class, to unlock plants, then you can go purchase Fluxweed Seed from The Magic Neep in Hogsmeade for 350 Gold.
You won't be able to grow Fluxweed or any other plant until you have completed quest 21, The Room of Requirement, which will unlock the Conjuring Spell and Room or Requirement.
Also, once you have completed Herbology Class, all of the plants will be available to purchase from either The Magic Neep or Dogweed and Deathcap which are both in Hogsmeade.
When it comes to growing plants, make sure you have a Large Potting Table which you can purchase from Tomes and Scrolls in Hogsmeade and use it in The Room of Requirement to grow your plants.
To find out how to get all of the other plants in Hogwarts Legacy, check out our answers page.
Did this help? 0 0 REPORTncG1vNJzZmivp6x7orzPoJimnaJjsLC5jqGmoK%2BRp8G0ecuenpqbqWS1sMOMraZmn5Wpeqe41LGunp2UYsCmscM%3D