Part of an ongoing series of 5e Rules notes.

It’s the damaging, crowd-controlling, Area of Effect spell that keeps on giving. You thought Entanglement was a pain in the ass? Try something (if you are a Druid or Ranger) that doesn’t prevent you from moving, just slows you and damages you when you try to: Spike Growth!

So what does it say?

The ground in a 20-foot radius centered on a point within range twists and sprouts hard spikes and thorns. The area becomes difficult terrain for the duration. When a creature moves into or within the area, it takes 2d4 piercing damage for every 5 feet it travels.

So we really have two effects here over the Concentration / 10 minutes of the spell:

1. The area of the spell is Difficult Terrain.
2. The area of the spell causes 2d4 piercing damage per 5 feet travelled.

This 2nd level spell would be somewhat effective at crowd control if all it did was slow the bad guys down. Causing 2d4 damage for every 5 feet (one square on a normal grid) traveled is murderous at early levels. A figure with a 30-foot move will be slowed to 15 feet (Difficult terrain), and take 6d4 (6-24) points of damage, with no AC or Save to mitigate it, each turn. And that applies to everyone within the spell area.

No, honestly, I have seem very large early mobs gutted by a well-positioned use of this spell.

This spell is particularly deadly because, while most “this area causes you damage” spells affect someone once per turn (e.g., Moonbeam), Spike Growth will mess them up for every square they move through. Plus, there’s no save.

Plus, it’s Sneaky

The spell notes:

The transformation of the ground is camouflaged to look natural. Any creature that can’t see the area at the time the spell is cast must make a Wisdom (Perception) check against your spell save DC to recognize the terrain as hazardous before entering it.

So you can set it as a trap for pursuers. If they don’t see it cast, they require a save to spot it before they blunder in.

Pushing In

There are a variety of ways of pushing or dragging folk into a Spike Growth spell area, from a Shove attack to Thorn Whip to Thunderwave to Thunderous Smite. It’s not always clear with these effects whether a target is dragged at ground level (in which case they would take damage each square of Spike Growth they were moved through) or somehow hurled through the air (in which case only the target square would cause damage).

The DM will have adjudicate based on the specific spell / effect and the circumstances it occurs in, to see how much damage the target takes.

Getting Out

The old saying of “Getting out means going through” is a losing proposition with Spike Growth. Going through means taking more damage.

Tactics for those caught in the spell:

1. Wait it out. Yeah, that’s not likely over 10 minutes, but one of your comrades might disrupt the Concentration of the caster.
2. Remove Yourself (Usually Vertically).  A long jump away, a high jump to grab something above, or, of course, some sort of teleport or flight can get you out of the area.
3. Enjoy the melee cover.  If you are a spellcaster or ranged weapon person, being stuck in Spike Growth isn’t nearly as problematic. Stand there and ranged-attack your opponents (maybe particularly the caster), knowing that the opposition melee fighters will likely not be charging you.

Limits of Growth

Spike Growth does not scale. Even with no save, at some point in the leveling/CR equation, 2d4 damage per square does not daunt in quite the same way.

Sure, it creates Difficult Terrain (always a good thing), and 2d4 over enough squares starts to add up, but a 15th Level character will be a lot less worried over it (or have ways around it) than a 2nd Level character.

But it’s good while it lasts.