You are going to want to do some research on 'how to grow onions' as they are not the usual garden vegetable. Here are several how-to bulletins to help. ;)

First you are using sets, not plants so that poses some problems. Second 2 months isn't nearly long enough, onion bulbs take 95-120 days to form depending on the variety. Third you have to find out what is the right planting time for your zone. Here it is January or early February for plants, March for sets but I don't know when it would be in your zone.

And fourth, you need the right type for your zone. Onions are day-length sensitive and come in short-day, long-day, and intermediate day types. We can only grow short-days varieties down here if we want large bulbs. Just a guess but I "think" northern CA would be long-day varieties and southern CA short day.

The site linked below is a good place to start your research. Hope this helps.

Dave

Here is a link that might be useful: Dixondale Farms - How to Grow Onions

Thank you for the link. I did do research, and the proper time for my zone is Jan. & Feb., but not sure if the chart I looked at related to sets or seeds. The sets were a gift, purchased locally, and the package is gone so I cannot be sure what they were.

Well, I'll let them go a while longer and see what happens. Thank you again for the reply.

Since you don't know the variety name then I would just make sure they are thinned out enough, not buried too deeply (onions are shallow growers), and then give them a couple of more months at least. Meanwhile keep them well-watered and well fed. Normally they aren't harvested until the plant tops break and fall over to lay on the ground anyway. You may not get any big bulbs but as the hours of day light get longer you will get some bulbing.

For next year you may want to ask over on the California gardening forum here when local gardeners plant and what varieties they recommend. Seed, plants, and sets all have very different planting times.

If all else fails you can always use them as green salad onions.

Dave

Concur: Concur all onion sets are long day storage onions. Varieties include Stuttgartener, Yellow Rock, Australian Brown, White Ebenezwer and Red Weatherfield. They are programmed to bulb on long days ( summer soltice). If you have nice healthy plants and they do not bolt (seed) you should have onions in July - August. Heat is usually the problem in the south., so we primarily use them for scallions (green onions) and grow short day onions in the winter.

Thank you both.

The day onions would come from seed, right? So next year start in January with seed?

I confess, have not fed them. What do you use? Something which will not encourage bolting, right? Are there foods formulated for onions and root crops to stimulate that growth rather than blooms?

Technically an onion is not a root crop. The "bulb" consist of layers of modified leaves. It is a heavier user of nitrogen than most vegetables. They are biennials so if they think they have lived through a winter and are mature enough, they will seed in spring.
I would think that in most zone 9's you would get plants of short day cultivars, set them in late fall for harvest in April. Works for middle to south Georgia.

All of the links I included above discuss those questions for you - including fertilizers. ;) But no, the various types of day length onions are available as either plants or seeds and as farmerdilla said, sets are all long-day onions.

So if long-day onions are what you need in your zone then sets would work. But if you need short-day or intermediate day length onions then you can buy either plants or grow them from seed. Seeds are usually started indoors a couple months ahead of time and transplanted to the garden at the proper planting time.

We can't tell you when to start your seeds as that depends on where you live and your zone 9 would have very different seed starting times than we do. Thus my suggestion to ask California gardeners that live in your part of the state.

Dave

From Northern CA: I buy sets from the big boxes in early Winter and plant immediately. They're called white, yellow or red onions, 60 bulbs in a package. About now in my raised bed they are reaching maybe a little more than a half-inch thick and yes, they are straight like a leek when you pull one. Good fresh or I barbequed one the other night and I liked the way that tasted too.
I don't know a lot about onions, but this is how I grow the sets from the big boxes and what I get. I also grow walla-wallas and you can definitely see those get big and round like your supermarket onions.