So surprised this spell doesn't have comments. It's so strong!! Automatic 2d4 damage for every 5 feet in a 20-foot-radius sphere outpaces even Cloud of Daggers, which deal automatic 4d4 damage. And when I say automatic, I mean no save, no attack, just damage — like Magic Missile does.

A lot of players like the idea of dragging their enemy through the field with a grapple, creating the sphere centered on a creature, or just pushing enemies through with a spell like Thunderwave. So many good things to do with this spell.

In my own home games, I often reduce this spell's damage to just 1d6 per 5 feet, and increase cloud of daggers AoE to a 10-foot cube to keep this other spell attractive to wizards and the ilk. I've experienced that this spell is still really powerful even like this, it's really crazy! Minions like Kobolds aren't going to notice the natural camo, and end up spearing themselves like a pileup on the autobahn. More power to the players though.

I was wondering, if I cast this spell on a zone that I'm on it, do I take dammage?

You don't take damage from being in the zone. Just if you move in it. 

This spell is overpowering to most enemies. As a second (edited) level Druid spell, our party Druid lays this down for every fight. With no restrictions on terrain placement they can cast it on a dungeon floor made out of solid rock, in a building with a wooden floor, as well as in the forest. If you have monsters reliant on closing the distance with the party, like a bunch of ogres, they could take as much as 16d4 damage if the had to traverse the entire distance between them and the party since it’s a 20ft radius (40ft). Weak undead Like zombies don’t have ranged weapons and this spell makes them ineffective as they close with the party.

My party has basically built their fighting style around this spell which goes to show it’s over powered. All have taken ranged weapons, staying at the outskirts of the spiked growth and shooting their enemies with ease. Ranged opponents stand a bit of a chance, but only flying opponents can completely avoid it.

My suggestion for a fix:

1. Apply 2d4 damage for each round spent moving within the area of effect on a failed dexterity save (half on a save). No other changes.

2. Or, I would recommend there be restrictions that this spell not be allowed to grow out of any terrain type unless it’s dirt or wood in nature and reduce the area of effect to 25ft diameter with no other changes to existing spell.

We will definitely be house ruling this at our table, but you would have thought this would have been taken care of in an FAQ by now. 

2d4 per round instead of per 5ft is a good suggestion.

Would the spikes from this spell be considered magical for resistance purposes?  Doesn’t make a lot of sense for something like a fire elemental to be affected. 

Quote from Nakaratu >>

Would the spikes from this spell be considered magical for resistance purposes?  Doesn’t make a lot of sense for something like a fire elemental to be affected. 

 Damage from spells is magical.

Quote from CooperS >>

My suggestion for a fix:

1. Apply 2d4 damage for each round spent moving within the area of effect on a failed dexterity save (half on a save). No other changes.

...

We will definitely be house ruling this at our table, but you would have thought this would have been taken care of in an FAQ by now. 

I will be following your suggestion.

Something is wrong when a 2nd level spell does automatic damage for every 5' traveled, while a 6th level spell like Wall of Ice has "moving through the sheet of frigid air for the first time on a turn" (with a saving throw to reduce damage).

I'm glad people know how strong this is. If you ever have any doubts about it's strength, look no further than Merilwhen's Meat Grinder. It was terrifying to behold.

My Druid loves this spell - gives plenty of time weaken charging enemies beyond Wild Shaping into a bear and biting their heads off

It's not a problem,  until it becomes a problem.  I used it extensively against the party in The Curse of Strahd!

I don't see why the terrain should have to be dirt or wood. Nothing in the spell description explicitly says that the spikes are organic (i.e., made of vines/branches/etc.). The spell is given to Circle of the Land (mountain or arctic) druids, which would seem to imply that they intended it to be possible that the spikes would be made of stone or ice.

I don't disagree that it's odd that the spell doesn't have any sort of save, but that's the only fix I think is necessary.

In prior editions there was a requirement for natural ground, but you’re correct. In this edition there is no such stipulation.

Can this be stacked with plant growth to slow down enemies for 8 feet for every 1 feet.

Two druids combo spike growth and grasping vine, with the vine in the middle of the spikes. If they try to run, grasping vine can drag them right back through the spikes for 8d4 piercing.

Your DM/PC's might cry.

Casting word is:

Surgicus Impailium

It's a good idea but monsters with higher speeds will take less overall damage. If you have ever ran through a forest, you will know that taking it slow is better than crashing threw.

Quote from LugnutNinetyTwo >>

I don't see why the terrain should have to be dirt or wood. Nothing in the spell description explicitly says that the spikes are organic (i.e., made of vines/branches/etc.).

 I'd house rule it so the caster has to use sharp(ened) stones (instead of sticks) to use it in dungeons.

This is such a great spell!

Its a great spell for druids. But it’s a real win for rangers. Compare this to what other martial classes get around levels 4-7 and it’s amazing. A level 5 paladin with a long sword, using an action to attack, and laying down a smite with a level 2 spell slot does 34.5 damage, requiring creatures in the spikes to just move 7 squares to equal the damage.

A level 11 paladin with a long sword, using an action to attack, and  laying down a smite with a level 2 spell slot does 45.5 damage, requiring creatures in the spikes to just move 9 squares to equal the damage.

This spell can effect multiple enemies, dealing multiple amounts of damage, and/or detouring them from moving much or at all. It lasts (concentration required) for 10 minutes! It doesn’t require plants in the environment to cast, so it can be used in dungeons and castles. It can wreck an enemy group in a small or medium sized rooms or tunnels and hallways.

Concentration? Yes. But no saving throw for the (magic!) damage, creates difficult terrain, and AoE all in one for just an action and level 2 spell slot. This stacks with several other things as well at higher levels. Plant growth comes to mind. 

I was just wondering if I cast the spell if I take damage from the spikes or not