Quote from Nereze >>

 If you use this on a mount and your riding it, do you grow too?

There are a couple ways to do this 
If you take the spell "Find Steed" you can make any spell you cast that targets only you, also target your steed, you can do this with either 6 to 10 levels in bard (depending on subclass) or 5 levels in paladin, then multiclassing as a sorcerer or wizard for 3 levels.
Then if you get on your found steed, and Enlarge yourself, you can also enlarge your steed
Or, if you don't have find steed, you could instead do the twin spell metamagic on yourself and whatever mount you've got

But it is?

@Nagog

 why is there no higher level of this spell? it just feels like this one lvl 2 spell is the only way short of an incredibly rare module specific potion to get a cool effect but its durration is incredibly limmiting.

I'm trying to play an Artificer that doesn't use magic (just engineering and maybe some alchemy), but I'm struggling on imagining a way to role this spell. Any suggestions? :D

If you use this on an immovable rod does it increase the dc to move it or give the person trying to move it disadvantage?

Unless you're using a mount from the Find Steed spell and you are the one that casts Enlarge. Find Steed allows any spell you cast that affects only you to also affect your steed. That would be pretty amazing. 

So going to use this on my 70 pound gnome wizard. He'll then get Mage Hand to pick himself up

Pumat’s so good an enchanter that he can use his enchantment abilities on transmutation spells.

Cant you make orc's mace so tiny he can't use it, or a piece of armour so big that the user can't move? I think that this is the best second level spell

" Choose either a creature or an object that is neither worn nor carried."

So no

If I cast this spell on myself as a gnome to enlarge myself, does it effect my movement speed? i.e. Does my movement speed go from 25ft to 30ft since I am now no longer a small creature while affected by the spell? if not, it's fine, but definitely something to think about.

Is it possible to make the enlarge spell permanent? Sorry I'm new "-v-

What if you cast enlarge on a gargantuan creature?

I actually came to DnD Beyond looking for an answer to this question. I had proposed this to my DM last night, and he ruled yes, but I'm looking for what others would rule.

The druid in my party cast Polymorph on our party rogue, who was down to 4hp. Turned her into a Dire Mammoth (Gargantuan). I then cast Enlarge. Session ended there, so nothing fun has happened yet with that combo.

Can you use the spell to enlarge/reduce yourself?

I wonder if I could use this on ranged ammunition as I throw it, essentially firing logs instead of arrows for more damage. Or throw a fist sized rock and turn it into a boulder. Or throw a sharp object into an enemy and then enlarging the object to essentially rip open the wound. So many possibilities!

Question if i enlarge a set of halfling-sized manacles and tie up a dwarf with it, then drop the spell?

Did the dwarf just lose his hands?

Object wasn't worn when i cast the spell...

Also what if a creature is carrying another creature?  there are many creatures that like to swallow adventurers whole...  All of a sudden the giant toad's acid reflux gets a little intense when he shrinks.  Or the other way around, cast reduce on your centaur friend...  Munch Munch, drop the spell....  Pop.

We need more clarity here!

If i reduce a canon ball so it fits into a musket, can fire it normally and end the effect on the way to the target? If so does it have the same range as the musket ball or does it drop suddenly? does it now do cannon ball damage?

Physics would say that it now travels at 1/8th of the speed, thus falling to the ground rather quickly. 

Quote from deathofhell24 >>

Quote from Nereze >>

 If you use this on a mount and your riding it, do you grow too?

 No. Only the target increases a size, not you. of course, you could use hombrew to change that.

 "If the target is a creature, everything it is wearing and carrying changes size with it. Any item dropped by an affected creature returns to normal size at once."

A mount carries a rider..!