Don't know anything about southern California but onions are about as easy as any vegetable in the east.
Variety is important. Short day onions are best grown in the winter. However they do vary apprecaibly in size and vigor among varieties.
For early December planting, seeds shoul be started around the first of September.
Sowing, I reccomend starting in a dedicated seedbed or flat. Georgia sun is still too hot for seedlings, so I place the seedbed in partial shade. I sow the seeds approximately 1/2 inch deep and keep the growing mix moist. I put 50 seeds per 12 x 18 x 2.5 inch flat. I use about the same ratio when I put in an in ground seed bed. I use gr0-mix in either case. Direct sowing is not feasible for me as open ground is too hot for germination. Also difficult to get spacing with direct seeding.
Transplanting. I just dig them up and transplant at the same depth that were as seedlings. I don't trim unless the seedlings are leggy. Most of the time, I can get them transplanted before this happens. Avoid burying any green plant of the seedling. Planting too deep is probably the main cause of onion failure.
Fertilization; Onions are actually in the green leafy group so they have a high nitrogen demand. So a high nitrogen amendment like composted chicken manure, blood meal or similar product should be incorporated into the seed bed followed by a high nitrogen sidedressing in early March. Short day onions typically began bulbing in March so you want to have the nitrogen available when they do. I am tradional so I have many more fertilizer choices.
Onions have a high water demand, so be sure to give them ample water during the bulbing process. A once or twice a week soaking in sandy soils is much superior to daily shallow watering.
{{gwi:101466}} {{gwi:85127}} {{gwi:101468}} {{gwi:101469}}

I'm so confused about the whole onion thing that I've never even tried growing them. But I always have green onions growing. I just plant the bottoms after I use the tops. In a green onion, is the white bulb called a bulb?

Deeby,

What is so confusing about growing onions?
You just need to sow the seed, transplant outside & harvest. :-)

This was my first year growing them and I agree they are very easy to grow.
But take a long time....

Here is a link that might be useful: {{gwi:101464}}

I plant long day onions as my lattitude is 41. I usually plant sweet Spanish from seed and white Ebenezer sets. I start my seeds in a flat indoors in Feb, and keep them trimmed to 6" for sturdier plants. Onion plants can be pretty fragile. You may want to try trimming your plants as they grow, not just before transplanting.
T I plant the seedlings as soon as I can work the ground properly. Weather and soil types usually make this a different time each year. This year we caught a break in a very wet, cool spring and got them planted late April. Then the rains came back. That brings me to a second consideration. I do not have raised beds, but I plant on hills (double rows for better usage of space). Then I mulch with wheat straw chaff. The hills keep the onions from trying to grow in soggy soil, and the straw keeps the soil temperature even (and moist, if necessary). After the plants are well established I side dress with urea. The pic is of Spanish onions I am now harvesting and curing.

The sets produce earlier onions that do not keep as well, but they fill the void in the seasons. {{gwi:101471}}

So, Terry, what do you do with all those onions? Do you freeze them, sell them? Nancy

Nancy, we use a lot for canning. Our spaghetti sauce has a lot of onions. We also can Serbian hot rice mix, salsa, Pamagiana sauce, sweet pickles. This year we have an overabundance since the Tomatoes are not producing well. I have sold some at the local farmers' market set up in one of the church parking lots, but in 2 weeks I only sold about 30. The onions alone wouldn't be worth the effort and space fee but we also had a lot of cucumbers, squash, beans, and dill. This was my first experience with selling, and I may not do it again as I'm just a home gardener and there are several people who violate the spirit of the market by bringing in stuff they didn't grow, and got at auction, etc.

But we have a big family and neighbors to whom we can always give the excess. And I have about 60 to harvest yet.

Goodground, it's the long day, short day, latitude stuff. It all has me going, "Huh?"

HUH?

It is really simple. If you live in an area, where the ground does not freeze in the winter. Zone 8 or higher. Grow short day onions in the winter. These are programmed to start bulbing with 10- 14 hours of daylight, roughly the March ( spring equinox). Intermediate day onions start bulbing at 14 -16 hours and are suitable for spring planting just about anywhere but are usually reccomended for Z 6-7. Long day onions require more than 16 hours of daylight to trigger bulbing which means many of them need the summer Solstice ( late June) to trigger bulbing.Z 5 and up.Many areas including this one are just too hot to grow onions in the summer time. I can grow some long day onions like Spanish, if I have a cool summer but they are quite iffy. Besides they take up summer space when I could be growing something else. Not that much competition for space in the winter.

It is really simple. If you live in an area, where the ground does not freeze in the winter. Zone 8 or higher. Grow short day onions in the winter. These are programmed to start bulbing with 10- 14 hours of daylight, roughly the March ( spring equinox). Intermediate day onions start bulbing at 14 -16 hours and are suitable for spring planting just about anywhere but are usually reccomended for Z 6-7. Long day onions require more than 16 hours of daylight to trigger bulbing which means many of them need the summer Solstice ( late June) to trigger bulbing.Z 5 and up.Many areas including this one are just too hot to grow onions in the summer time. I can grow some long day onions like Spanish, if I have a cool summer but they are quite iffy. Besides they take up summer space when I could be growing something else. Not that much competition for space in the winter.

The above posters have covered the subject very well... just adding a few pictures.

I'm in south Louisiana so probably not much different than the OP.

Seed Planting time - late September to early October. my favorites are Granex 33 and Texas 1015 (Supersweet)

Planting method - sprinkle in seed boxes, no thinning. The plants have straight roots so they separate easily.

{{gwi:101472}}

Set plants - December when pencil size
{{gwi:101473}}

Fertilize rows - Around February
{{gwi:101474}}

{{gwi:101475}}

Harvest - May
{{gwi:101476}}

Lovely pictures, Farmer D and Grandad! I know Farmer D said, but I was so pleased when I got huge onions, I thought I would repeat it- nitrogen! Two times before bulbing, once at planting and once when they are nice and tall but have not been triggered to bulb.

Thanks all. Clears up a few things. Didn't realize you want to let them get pencil size, for one.

Grandad: how deep is that box? How deep should a tray be if I was to start in a tray? How much do I trim the roots? And can you mark on one of your seedlings' "bulbs" about how deep it should be planted? Thanks.

Deeby: we're in short and intermediate range. Both mine are shorts. Hybrid Granex Yellow PBR and Red Burgundy. Here's a decent map of the county and planting dates for most veggies. I'll add an extra -- snow peas are best started in late Oct/early Nov. here is Santee.

Kevin

Here is a link that might be useful: San Diego county veggies

woohooman, The wooden (homemade) boxes are 4 inches tall with about 3.5 inches of soil. Bottom is made from scrap sheet metal...(In my case, made from discarded metal signs.) Plastic boxes are 7 inches tall with about 5.5 inches of soil. No difference in results with either box type for onions. However, I do find that the wooden boxes generally do better for many other seedlings. Plastic boxes tend to hold more moisture and some plants don't like "wet feet". Wooden boxes don't have this issue but they do need more frequent watering.

I usually plant my onions about an inch or so deep. In the above picture this would be covering about half of the white part of the stem.

Onions can be planted smaller than pencil size, which would be in late Novermber (for me), but I find that plants are less fragile if I wait. Also, IME the larger plants tend to start growing sooner so there is no advantage to setting plants earlier.. might be because of our milder December climate.

This post was edited by grandad on Sun, Aug 17, 14 at 12:28

Hey Kevin, it's only after 10AM and it's so hot I feel sick. You must be boiling out there. How do your toms do in heat like this? Guess what I'm doing-after I use up a gallon of spring water I fill it with tap water and have quite a collection now. It's for if we get told we can't water our plants. I'm going to keep doing this until I have about half a garage full of gallons.

Thanks grandad!

Deeby: Yep. It's hot. My maters? They'd be doing excellent if it wasn't for this fricxin Tomato Suck Bug! Actually, I water a bit more(maybe), but I'm still on one good weekly soak. Mulch does wonders!

Kevin