Potential for frost
Sudden rain and shorter days
Just as natural cycles cause plants, animals, and insects to draw closer to home, move around or grow less, and to retain resources, we can copy those behaviors to the benefit of our garden and landscape. While there is still time to plant onions, poppies, spring blooming bulbs, winter crops mentioned in the October notes, and cover crops, November is an excellent time to clean up and prepare for the holidays and colder weather.
As trees drop their leaves, think before you rake. Fallen leaves make excellent compost or mulch but they will interfere with your lawn, if you still have one. Leaves should be removed from lawns and concrete (due to staining), but there is no reason that I know of for removing leaves from anywhere else. From my point of view, fallen leaves are plant foods and soil amendments that have been around a lot longer than us. The only exception might be leaves that are exposed to a lot of car exhaust. You might not want to add those amendments to your soil. Also, really thick layers of leaves, more than a couple of inches, can interfere with soil respiration. If you have that many leaves, it is a good idea to chip them, or chop them with your lawnmower to speed decomposition up a little bit.
Cooler temperatures may reduce the number of pests in your garden and landscape, but imported cabbageworms, brown marmorated stink bugs, and Harlequin bugs, along with ever-present aphids, will be doing their very best to wreck your cole crops. Cabbages, cauliflower, and broccoli leaves should be checked frequently for imported cabbageworm butterfly eggs (tiny clear-ish white flecks on the underside of leaves), small (and some not-so small!) green cabbageworms, and clusters of drum-shaped Harlequin bug eggs. These eggs can simply be extermigated (brushed off) and the hatched larva will generally be unable to find their way back to the host plant. You can also use row covers, once you are absolutely certain that you have removed all the eggs. [Check every few days anyway, just in case.]
Fall clean up
If you haven’t already, this is a good time to discard any plants that are not thriving. Annuals and other garden plants that have completed their life cycle are best removed by cutting at ground level, rather than pulling. Pulling plants up by the roots disrupts microbe populations, which interferes with soil health. Also, by cutting plants off at root level, you may get a surprise next spring when that annual turns out to be more tenacious than you thought!
Fires can be devastating. Dried brush, dead weeds, and stacked firewood can speed a fire closer to your home than anyone wants, and can provide shelter for rats. Well-watered plants are less likely to catch fire. It is all too easy to think it won’t happen to you, but it can. Change the batteries in your smoke detector, have your chimney and/or furnace inspected, and look at your landscape with an eye for fire safe gardening.
It may be difficult to imagine frost in California, but Santa Clara Valley's first frost date is November 15th. Frost dates are statistical averages over time. They are not written in stone. I can tell you, speaking from experience, it is far easier and more comfortable for you to prepare your plants' frost protection against winter sunscald and frost cracks before it is needed. Old bedsheets, row covers, and even umbrellas can provide all the protection that's needed, just be sure to make it so that the fabric does not actually touch the plant, or you defeat the purpose.
Some California winters are wet and others are not. Until regular rains occurs, your plants will still need to be watered, though not nearly as often or as much as during the peak of summer. An inexpensive moisture meter can help you see which plants need more water and which do not.
You can stabilize soil temperatures, reduce weeds, and slowly add nutrients to your soil with mulch. You can buy different sizes, colors, and materials, or you can contact local tree trimming companies for free mulch. Wherever it comes from, be sure that it is disease-free and that it won't float away when the rains comes.
Sooty mold fungus
Remember those aphids, mealybugs, whitefly and scale bugs that tormented your garden all summer? Well, they left behind copious amounts of honeydew that create the perfect growth medium for mold. Sooty mold is common in San Jose, California, and is easy to recognize as black smudges on leaves and fruit. While the mold can be washed off food and eaten safely, it can be devastating to host plants. The mold actually blocks sunlight from entering the leaves, slowing or even halting photosynthesis. Ants carry the disease, so slowing ant traffic can be a big help. The easiest way to block ants is to wrap tape around the trunks of trees and apply sticky barriers to the tape. Also, trim branches away from buildings, fences and other plants, and use ant bait. While you are at it, November is also the perfect time to caulk your home against winter invaders.
Before the rains get started, this is a good time to look through stacks of materials to see what needs cleaning, repairing, sharpening, or discarding. Plant saucers and pots should always be scrubbed clean and then soaked in a household cleaner, such as Lysol, for ten minutes to prevent the spread of disease. They should also be stored upside down or on their edge to prevent water collection and mosquito breeding. I used the staves from a half barrel that fell apart to create a simple storage system for planter saucers. I just drilled screws in from above. It makes them easy to see and they do not collect water.