Seed of Yggdrasil in Valentine's?

Looks like they come from the 20 AP Rider/Caster/Assn./Berserker Node but I don't think it is very efficient to farm them during this event since I didn't hear a single guide I read/watched mention them so you are prob better off farming them outside of this event (I believe).

If you look through each battle's page, you can see what each one drops.

Looking at the NA drop rate sheet, it says 133 AP/drop, and the best outside the event is 40 (Babylon) and 58 (Okeanos), so I would also say it's not worth it.