Ok but if we are starting paying for college next year it won’t really have time to grow much. Right?
Correct, as long as the 529 money is used for qualified expenses. If not, then you will pay taxes on the investment earnings, and in may case a 10% additional tax (“penalty”) as well. It takes good planning.
529 contributions must be made in cash, so liquidating another investment to fund a 529 may itself bring a big tax bill.
A simple example, if you are planning to pay a $10,000 tuition bill in October and you have a $10,000 bank cd that matures in September, you can transfer the proceeds of your cd to a cash equivalent fund in your 529 account and the interest you earn (however much that may be) for the period of time before you pay the school will be tax free
We live in MI, so it looks like maybe a Michigan Education Savings Program may be a better option than a 529 for any tax benefit. My daughter is probably going to U of M or Michigan State (has been accepted to both but we’re waiting on financial aid packages, etc. for her to decide). Thank you for all the information shared 
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The MESP is a 529 plan. Using that plan as a Michigan resident gives you extra state tax breaks. I would highly encourage it. I wish we had something like that in my state (NJ)
If I were the OP and I lived in a state that offered any sort of a deduction for 529 contributions, I’d certainly open one to pass the funds through each year.
I have a 529 account for each of my kids. I still contribute each month so that I can take advantage of my state’s deduction. We will continue to take advantage of the tax deduction for many years, likely long after they graduate. We long ago realized that the plans are just one more legal way to pass down a bit of $ to our kids and we are fortunate enough not to need them for college expenses.
Eventually we will reassign the accounts and hand them over to our kids. They can choose to hold them for any future kids, or pay the taxes/penalties and use the $ for anything they want.
Most 529 plans should allow you to choose the level of investment risk you wish to take. Typically, the 529s for high school seniors and those attending college are in the lowest risk investments which have the lowest yields. As other posters have said, any income you get in your 529 is tax free as long as it is used for approved educational purposes.
Our state doesn’t offer any tax breaks for 529s, so we have ours in another state. Beware of nuisance fees–in our 529 account, if you don’t invest at least $50 a month, you get hit with an account maintenance fee, so be sure you understand the fund rules and fees they charge.