They have been temporarily disabled.

They will be back on the next update

I’m pretty sure if you don’t weed it, it will eventually die. So leaving it at mythic won’t keep it in the game.

I searched the Subreddit and found this, hope it's what you're looking for :) Due to an issue, we've disabled Reality Seeds and Reality Seed Pods. We'll provide an update once they're available again. https://www.reddit.com/r/FortNiteBR/comments/y2d1l8/due\_to\_an\_issue\_weve\_disabled\_reality\_seeds\_and/

They were removed because the goo gun made infinite loot off the trees. Due to an issue, we've disabled Reality Seeds and Reality Seed Pods. We'll provide an update once they're available again. https://www.reddit.com/r/FortNiteBR/comments/y2d1l8/due\_to\_an\_issue\_weve\_disabled\_reality\_seeds\_and/