I just checked in my overview and it said that I earned a new title: the tender

I have no idea how I got this title, could anybody explain how/why I got this title all of a sudden?

"The Tender" is a title earned during Spring fest. Here's from the spring overview post:

The Tender: Tend other player's Flowers at least 25 times.

You must have tended other players gardens. :)

These are the other titles that can be earned during this fest in case they pop up. (They're a lot harder though.)
Green Thumb: Harvest at least 1 of every Regular Flower species.
Fabled Green Thumb: Harvest at least 1 of every Fabled Flower species.
Majestic Green Thumb: Harvest at least 1 Majestic Flower Pet.
Omniscient Gardener: Harvest at least 1 of all 22 Regular/Fabled Flower Pet species and any 3 Majestic Flower Pets.
Premier Green Thumb: Harvest the very first Flower Pet.

So, congrats on the new title. ;)

Thanks!