For onions, be sure you check with your local extension office to find out what varieties to plant and when. Ask about spinach varieties and planting times while you are talking to them, there may be a regional issue, or you may have had a bum pack of seeds.

So you know, I have had good luck with Swiss Chard (Fordhook Giant in particular) as a warm weather alternate to spinach.

I'm in zone 9b and find that chard is much easier to grow than spinach. As for potatoes and onions, your lack of success my be due to growing varieties than need colder winters. The best potatoes for our climate are the small ones. Big russet potatoes need colder soil temperatures than we have in zone 9.

Thanks for the thoughts and advice.

Much appreciated!