Congratulations, You have survived another San Joaquin Summer
September has arrived! Having grown up on a vineyard ranch (near Raisin City!) I remember September and the fall raisin harvest. Cool mornings and hot days then cool evenings with a nice breeze.
Your plants will feel the change too. Now would be a good time to trim and fertilize. Many flowering shrubs (especially roses) will respond with blooms similar to spring. Annuals (those that survived the heat and bugs!) will really benefit from a light fertilizing now. Be careful what you prune since many shrubs have buds already set for spring blooming. Heavy pruning may eliminate those buds. Azaleas, camellias, forsythia and viburnums are a prime example.
Pre-emergents like Dimension, Amaze or Surflan should be applied now for winter weed control. It's so much easier than trying to spray weeds down during cold wet weather, I'm surprised more people don't take advantage of it. Don't use these products where you'll be planting fall annuals or over seeding lawns.
You should be enjoying a second round of summer vegetables or maybe start clearing the bed for fall planting. Mid September to early October is the prime time. Cabbage, cauliflower and broccoli need enough warm weather and sunlight to set buds before cooler weather. Planting lettuce, onions and other leafy vegetables is not as time critical. Do check the weather before planting, a short heat wave (100*F or more) will wilt young fall seedlings. Hold off until the temps cool. Also be on the lookout for those cute white and yellow butterflies in the garden, they're laying eggs of voracious worms! Light weight row covers or frost fabrics work great at protecting against the heat and as a barrier for bugs. You can keep the frost cloth on all winter. Add an organic mulch to areas that were planted this summer to replenish nutrients and beneficial microbes.
If you have a Bermuda lawn, mid September to mid October is the optimum time to over-seed with perennial rye (NOT annual rye) for the winter. This is also a good time to plant or repair fescue lawns by over seeding bare or thin spots.