Do your plots need to be easy to summarize in a query?

A query is not a summary. A query is a sales pitch.

Focus on what is important, focus on the hook, the character and anything that makes your book unique. You're selling your book, simple as that, you should not even be trying to describe your book.

Later on the agent may ask for a synopsis, THAT is a summary, but it should still be interesting and catchy, not a laundry list of things that happen.

Ditto what Drachen Jager said.

The query should include main character(s) and their conflicts/choices, not a summary.

Cruise around the forum looking for query advice, and take a look at the Successful Query thread to get a feel for what a query is and isn't.

Forget about agents for a moment. A customer walks into a bookstore. They have thousands of books to choose from. They read back cover copy and try to pick the one that interests them the most.

Ultimately, that is the person you're selling your book to. Now write a pitch to convince them your book is something they want to read.

Read the jacket synopsis on a published novel. This is how you summarize a plot and keep the excitement in. This works well with queries, and with synopsis. And any good query letter darned sure is an exciting read, and offers a solid, vibrant symmetrization of the plot.

Whether such copy excites you or not, this is how many, many readers choose a book, and it flat works. It's also how you have to sell a book.

Saying your plots grow out of character has nothing to do with it. Most good plots grow out of character. Bland is the choice of words you use to describe the plot, not the plot itself.

If the plot really is bland, you have a bigger problem than how to write a query.