I was running a combat for a ranger character, and the player claimed Land's Stride allowed them to not take the 2d4 damage per 5 feet of movement from the Spike Growth spell. Is this accurate?
The text of Land's Stride reads the following (emphasis mine):
Starting at 6th level, moving through nonmagical difficult terrain costs you no extra movement. You can also pass through nonmagical plants without being slowed by them and without taking damage from them if they have thorns, spines, or a similar hazard.
The spell Spike Growth creates difficult terrain that lasts until the spell ends, either by its duration running out or breaking concentration. This difficult terrain being an effect of the spell, it is indeed magical. For more information on what is or isn't "magical", this question treats the subject more in depth than I could explain here without going off-topic.
Because of that, you cannot apply Land's Stride to it. You'll still take the damage and have the difficult terrain movement penalty.
They're wrong. Their ranger would still take damage
Land's Stride specifically says moving through nonmagical terrain costs no extra movement. Before going on to say:
You can also pass through nonmagical plants without being slowed by them and without taking damage from them
Spike Growth is a spell (with a 10 minute/concentration duration) and therefore its ongoing effect is magical.