Spinach has been hard for me to grow without bolting but I think I've had the best luck with fall sewn seeds that didn't germinate till the next spring.

Spinach is a cold weather crop, so does a bit better in the spring/fall vs the hot summer. Depending on weather next year, you could try them earlier!

I planted spinach seeds in a container outside on March 16th. They started sprouting a couple of days ago.

This is my first time planting and I'm wondering if I could get them in the ground even earlier next year?