Pea seeds, ripening tomatoes and nitrogen

Can I save some of my peas to plant next year, or do I have to buy seeds?

There are only complicated answers to your question, not a simple yes or no. Here is a list of things to factor in:

Although peas are among the easier seeds to save because the flowers can pollinate themselves, be sure that your peas are open-pollinated. The seed packet will tell you, or it will describe them as an heirloom variety. That means the same thing.

If your peas-or any vegetables in your garden-are hybrids, do not save the seeds. Those seeds will be like some distant ancestor, not like your current garden crop....