These are all generalizations and they apply to The Learning Garden, located in Sunset Zone 24, less than 3 miles from the Pacific Ocean in an alluvial plain that is barely above sea level. Cold air from the surrounding higher elevations drains into our area and we are reliably cooler than much of the surrounding areas.
If you are growing inland from us, your temperatures will fluctuate more than ours. The further from the ocean a person gardens, the temperatures become less moderate and the effects of heat and cold are more pronounced. While we can grow some cool season crops year round (kale and chard for example), this becomes more difficult without the ocean's pronounced influence.
Plant in the ground: lettuce, carrots, beets, parsnips, potatoes, celeriac, radishes, spinach,
Plant in containers: lettuce, cabbage, broccoli, kale, chard, (these last two can be started now, but they would have been better started earlier – their production will be reduced by the coming warmer weather), peas, fava beans, lentils, garbanzo beans
Otherwise: You are looking in seed catalogs and reading books to figure out which tomatoes, peppers, beans and other summer crops you will be planting. You will order too many seeds despite promises to yourself to not do it this year.
Plant in the ground: lettuce (and other salad greens), carrots, beets parsnips, radishes, spinach, purple beans,
Plant in containers: early tomatoes, basil, cucumbers, summer squash
Otherwise: If you haven't over-ordered your seeds for summer yet, get busy. You're not playing by the rules.
Plant in the ground: purple beans, lettuce, radishes, purple beans, beets, radishes, spinach, set out plants of basil, early tomatoes, later in the month, sow early sweet corn,
Plant in containers: tomatoes, basil, peppers, eggplant, cucumbers, melons, all squash,
Plant in the ground: beans of all colors, lettuce, radishes, beets, spinach, set out plants of tomatoes, peppers, eggplants, basil, you can start planting all corn now
Plant in containers: tomatoes, basil, peppers, eggplant, cucumbers, melons & squash, okra,
Plant in the ground: all basil, eggplant, all melons and all squash (including cucumbers, set out plants of same and all tomatoes, eggplants and peppers) green and yellow beans and all the dried beans; corn too, if you have room
Plant in containers: As in April, but it's getting late – peppers, eggplants and basil are still OK to start, but it's getting late, did I say it was getting late?
Plant in the ground: all the above, but it's getting late... you can still get a crop, but it will be cut shorter by any early cool weather; the last of the corn can go in early in the month
Plant in containers: after starting pumpkin seeds, take a nap
Plant in the ground only out of necessity – extreme necessity
Plant in containers: continue napping
Otherwise: You can begin to think about your cool season seeds now. Get out them catalogs and prepare to over-order those!
Plant in the ground: nothing if you can avoid it
Plant in containers: towards the end of the month, in a shaded location, the first of the winter veggies can be started, cabbage, broccoli, kale, chard, fava beans, leeks, shallots, onions...
Otherwise: You DO have your cool season seeds ordered, yes?
Plant in the ground: nothing, until late in the month, start sowing turnips, parsnips, radishes, beets and carrots – keep seeds moist! Peas, lentils and garbanzo beans can be sown...
Plant in containers: Cabbage, broccoli, kale, chard, favas, cauliflower, Brussels sprouts,
Otherwise: Get your garlic bulbs, shallot bulbs and onion sets ordered – don't wait – they sell out!
Plant in the ground: by now you can begin to set out some of your cabbage, broccoli, kale, cauliflower, chard and so on. Continue with seeds as above... you can also direct sow favas if you want. Potatoes can usually be found about now as well as sets or seed bulbs of onions, garlic and shallots and they all should be planted from now until late November.
Plant in containers: More Cruciferae and favas, celery and celeriac,
Plant in the ground: More of September's plants can be sown – you still have time for all of them except onions, this will be the last month to plant peas, lentils, garbanzos, shallots, garlic and fava beans. Their growing season is too long to get the harvest you would want. Although the legumes can be planted if you are willing to take a lesser harvest or are using them as a cover (green manure) crop.
Plant in containers: I'm still sowing cabbages, broccoli and cauliflower, but Brussels sprouts are a longer season item so they're not a part of my efforts until next season's planting begins.
Plant in the ground: Too little light and too many parties make it difficult to find garden time – but if you have some things left over from November, try to get that done.
Plant in containers: Pretty much the same story, if you have time, do more of all that's listed from November.
There are two big shifts in Southern Californian gardening: At the end of September, beginning of October it's all about the winter crops. At the end of February, beginning of March, the focus all shifts to summer and the heat lovers. Seeds get started slightly before then (if you have the right conditions, up to six weeks before then!).
(Sorry this took so long to get up - I had to 'refresh my cache' to post.... Who knew I had so much cache?)