Conifer Wurm — ruling 1

The value of X is determined only as Conifer Wurm's ability begins to resolve. It won't change later in the turn if the number of snow permanents you control changes.

Conifer Wurm — ruling 2

Because Conifer Wurm is itself a snow permanent, its ability will usually give it at least +1/+1.

Conifer Wurm : règles, fonctionnement et interactions (MTG)

Conifer Wurm is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Trample : This creature gets +X/+X until end of turn, where X is the number of snow permanents you control.

How it works : Conifer Wurm

Original English text — Wizards of the Coast / Scryfall

#1June 14, 2019· Wizards of the Coast
The value of X is determined only as Conifer Wurm's ability begins to resolve. It won't change later in the turn if the number of snow permanents you control changes.
No other card is named in this ruling.
#2June 14, 2019· Wizards of the Coast
Because Conifer Wurm is itself a snow permanent, its ability will usually give it at least +1/+1.
No other card is named in this ruling.