Southern California Coastal & Inland Valleys
Sow carrots, lettuce, and spinach a dozen or so seeds at a time every two or three weeks from now through October. This will provide a succession of succulent harvests through the winter. Leafy green plants like lettuce and spinach that are three or four inches tall and wide--or carrots that are at least one-half inch in diameter--before the first hard frost will be mature enough to provide harvests through early spring. If they're smaller, they'll not provide much to eat until spring, when they may bolt first.
Why Sow Onion Seed vs. Sets?
Sowing bulb onion seed now will provide green onions throughout the winter and small bulb onions in late spring. Dig these up when their tops dry, and replant them as sets after the following January's frosts. They will develop into full-size bulbs the following summer. (The set-size bulbs that are larger than a dime may bolt when replanted, but they can be used in winter recipes as "pearl" onions, or used for their greens.)
Fruit Tree Clean Up
Pick up and destroy fallen fruit. Prune and destroy dead and diseased limbs, and remove any suckers, long shoots that grow straight up from the trunk base, or watersprouts, long shoots that grow straight up from a branch. Keep tree trunks, especially those of young trees, painted with light-color, matte-finish, indoor latex paint to protect them from sunscald. Remove bird netting; if you leave it in place, it will become enmeshed in new shoot growth. Rake the area beneath each tree bare, and apply a new mulch. These clean-up efforts will prevent diseases from spreading and harmful insects from hiding for the winter.
Fruit Tree Watering, Not Feeding
Water trees deeply, but stop feeding trees later this month or the resulting tender new growth may be damaged by winter frosts. The gradually cooling weather and lack of additional nitrogen fertilizer during September, October, and early November will help harden exuberant summer growth to withstand winter's cold.
Trim Flowers For Repeat Bloom
Remove faded blooms of perennials like coreopsis, Shasta daisies, delphiniums, penstemons, and yarrow. Cut them back to within six inches of the soil, and they may bloom again in the fall. Divide clumps that are too large or no longer blooming well. Sidedress the plants with bonemeal and compost, and water in.