REDU format ruling
The World Tree

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)Each time a face-up Plant-Type monster(s) on the field is destroyed, place 1 Flower Counter on this card. You can remove any number of Flower Counters from this card to activate these effects.
● 1 Counter: Target 1 Plant-Type monster on the field; that target gains 400 ATK and DEF until the end of this turn. (This ATK gain remains even if this card leaves the field.)
● 2 Counters: Target 1 card on the field; destroy that target.
● 3 Counters: Target 1 Plant-Type monster in your Graveyard; Special Summon that target.
Rulings
- Placing Flower Counters onto The World Tree does not start a Chain.
- Each of The World Tree's effects target. Each effect is an Ignition Effect.
- If the Monster Type of a monster on the field is changed to Plant-Type with DNA Surgery, when it is destroyed, place a Flower Counter onto The World Tree.
- If a Plant-Type monster is destroyed by battle, place a Flower Counter onto The World Tree when the destroyed monster is sent to the GY. If a Plant-Type monster is destroyed by a card effect, place a Flower Counter onto The World Tree after resolving the effect that destroyed the Plant-Type monster.
- If The World Tree is removed from the field after resolving its Remove 1: effect, the ATK and DEF increase still lasts until the End Phase.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.