Do you need to know grammar to be a good writer?
No. Not really. But you do need to know it.
My mother-in-law is visiting. Among other things, she teaches English. She was talking about some of the grammatical things she was teaching students this year, listing off a bunch of terms. It was enough to make Mr. Miriam-Webster himself go cross-eyed. (Mr. Miriam-Webster is the fictitious child of Mr. Miriam and Mr. Webster who flings dictionaries at evil-doers.)
I commented that I was glad I never had to learn those terms. Honestly, I’m convinced it’s not necessary to know the terms to write well.
That said, you do need to know how to use grammar well, whether or not you know the terms. Grammar tells you how to communicate what you want to communicate. How do you form sentences? How do clauses come together to form thoughts? If you use bad grammar, you’re not communicating effectively. You leave your reader frustrated. (My editor notes that your editor also won’t kill you if you use good grammar. I’m in favor of non-homicidal editors, so please, use good grammar.)
Growing up, I read… pretty much everything that was science fiction or fantasy that I could lay my hands on. I absorbed not only stories, but how those stories were told. When someone useded badly grammar, I wouldn’t be able to tell you why it was bad, but I knew it wasn’t good! When it came to grammar classes at school, I’d always shrug. “Well, duh. Of course that’s how you write!”
I didn’t know the terms, but I knew the grammar.
And that’s something a writer needs. Even if you don’t know why we communicate using certain rules, you do need to have a feel for what’s correct and what isn’t. You need to use the grammar of our culture to convey what you want to convey. Some people are able to pick that up just by reading. Other people really do need the explicit instruction.
But if you don’t need to know the terms, is there any benefit in learning them?
Oh, yes. Even though you don’t need to know those terms, that knowledge will only help you in the long term. When your editor tells you to avoid passive voice, you need to know what she’s talking about. When your beta readers complain about too many run-on sentences, you need to know what those are. When a writing mentor suggests using fewer adverbs, well, how do you identify them?
So while you don’t need to know the grammar terms, well, I’d still suggest learning them. Those terms aren’t useless facts and trivia. They will help you track down your weaknesses in the mechanics of communication.
So, sure. You don’t need to know grammar, but you do need to know it. Invest in some growth if that’s a weakness of yours. Pick up a good grammar tool. I know writers that swear up and down by Strunk and White. That’s probably a great place to start for adult writers.
But make sure you know how to communicate. Use that grammar!