With the soil so thoroughly soaked, it would be a shame not to take advantage of one other fall planting opportunity--to plant a tree or some shrubs. Both require big holes, which are a whole lot easier to dig in a moist soil. But if your soil is still soaking wet from the rain, let it dry a little more.
Trees and shrubs can be planted in almost any season, but they enjoy an advantage planted in the fall. This is the time of year when their roots do the most growing.
Research suggests that plants favor spring for leafy growth and summer for flowering or making fruit. In autumn, the roots get all the plant's attention, so a tree or a shrub planted now will immediately begin growing roots out into the soil, quickly becoming established in its new home.
You won't see much happening above ground until spring, but below-ground roots will reach out into the moist, warm soil. A year later, a tree or shrub planted in the fall will be double the size of one planted in the spring, simply because it will have the roots to support the above-ground growth.
There are some exceptions. Truly tropical plants such as bougainvilleas and hibiscus may not be on this same timetable (no researcher has looked into the matter), and you definitely risk damage from winter frost, which a plant is most susceptible to when young.
Deciduous fruit trees may be another exception--trees such as apples and peaches and plums--and they are a better buy in the middle of winter when they are sold bare root.
Most deciduous trees--such as liquidambars, birch and sycamores--and the few deciduous shrubs we grow do seem to benefit from fall planting, even though they are about to lose their leaves. This is suggested by research originating on the East Coast and in the Midwest.
Research back East has turned up another surprising fact that most likely applies to California as well--that the common practice of digging big planting holes and adding lots of amendments to the soil that goes back into the hole (the backfill), may not be such a good idea. Astute gardeners will immediately note that this means planting a tree or shrub may be easier than thought.
As reported in Avant Gardener magazine, trees planted in a large hole filled with well-aerated soil make dramatically more growth the first few years but in the long run, they may be poorer trees as a result. Trees planted in smaller holes, with the soil going back in the hole being only slightly amended or not added to at all, start more slowly but become better established.
The explanation is enlightening: A well-prepared planting hole becomes much like a container after a few years, the roots preferring to circle around inside this good soil, rather than venturing out into the native soil. So the plant becomes pot-bound, on a big scale.
It is also less able to endure drought of any kind, because the tree is essentially growing in a large container and doesn't have as large a soil reservoir to draw upon.
So how does one plant a tree or shrub? Dig a hole no deeper than the root ball but roughly twice as wide. Set the soil aside and pulverize it so there are no clods and perhaps add a little soil amendment.
If you have a very heavy soil--adobe or sticky clay--and you suspect that the soil stays soggy for days after watering, you can dig a hole in the bottom of the planting hole that will act as a drain. Use a post-hole digger so it isn't very wide, but is deep. Try for three feet. Fill this drainage hole with a mix of soil and soil amendment, or some suggest with pea gravel.
Take the plant out of its container and with a knife, make four evenly spaced slits down the side of the root ball, cutting about one-half inch deep. Continue these slits across the bottom of the root ball so they make an X. Cutting the roots like this will force the roots to regrow out of the root ball and into the surrounding soil, but to make sure, pull the roots gently away from the root ball where they have been cut so they are pointed in the right direction.
Now set the plant in the planting hole, making very sure it will not end up deeper in the ground than it was in the container. If anything, the base of the plant (the "crown") should be slightly higher than ground level. Put the soil back in the hole, pressing it down so it is not too porous.
Prevent Drowning Plant
Mound up a temporary basin of soil (with what's left over) around the plant to help funnel water to the roots when you water, but rake it flat again during rainy weather so the plant doesn't drown.
Trees should be staked, but not with the flimsy affair it came with. Use 2x2-inch stakes placed on either side of the trunk, each about a foot away from the trunk, and tie the tree with that green plastic plant tape between the stakes. This lets the trees sway in the breeze so it can develop the strength to stand on its own. Never tie trees directly to their stakes--stake and trunk must not touch.