Mild winter weather on the West Coast limits the choices for autumn color. So many of the trees, shrubs, vines and perennials that get so colorful where autumn weather is cooler do not get so colorful here. Mild weather also allows so many more evergreen plants and plants that do not get colorful in autumn to thrive here than in harsher climates. Consequently, the tougher and more colorful plants are not so common.
Fortunately for those who appreciate autumn color, there are a few choices that do not mind mild weather. The three most reliable trees for autumn color are sweetgum (liquidambar), Chinese pistache and flowering pear. All three turn yellow, orange and red. Maidenhair tree (gingko) is just as reliable, and turns bright yellow, but lacks orange and red. (‘Saratoga’ gingko turns pale yellow.)
If the weather is right, fruitless mulberry, tulip tree, black walnut and the various poplars display clear yellow foliage. Eastern redbud can do the same, but is a small tree. Smoke tree and crape myrtle are large shrubbery or small trees that can get as colorful with yellow, orange and red as Chinese pistache does. Japanese maples have the potential to turn yellow or even orange, but more often turn dingy brown.
Grapevines and wisteria are vines that can be somewhat colorful if they hold their foliage long enough to get noticed. Boston ivy, which is actually more closely related to grapevines than to ivy, is the most colorful of the vines in autumn. Unfortunately, it can be too destructive to paint, wood and whatever else it grabs hold of to be practical for home gardens. It works nicely on indestructible concrete walls.
Heavenly bamboo, which seems to have appealing but distinct foliar color for every season, turns richer shades of reddish bronze through autumn. Some cultivars turn rich brown. Others become more purplish red or burgundy. Unlike other autumn foliage that sooner or later falls through winter, heavenly bamboo is evergreen, so hold its color until it get replaced by another color in spring. Unfortunately, there are not many other evergreens that turn color in such mild weather.
Autumn is slow in getting here. Yes, as of last Sunday, it is now autumn. The date is determined by the equinox, so is the same for everyone in the Northern Hemisphere, and is the same for the arrival of spring in the Southern Hemisphere. It just takes a bit longer for autumn weather to develop in the mild climate here. Nights are cooler. Shorter days are not as warm as they had been.
It might seem like autumn color is a bit early this year. In the wild, where there is no irrigation, native box elders, and maybe some of the cottonwoods and sycamores, are already yellowing. The box elders are already dropping some of their foliage. However, this is not caused by an early chill. It is caused by late warmth after an otherwise mild summer, and might inhibit better color later.
Autumn color is different every year. Sometimes, early and sudden cool weather after a mild summer promotes good foliar color that lingers longer while relaxed trees slowly realize that they should probably start to defoliate. Sometimes, early wind and rain accelerate defoliation of otherwise good color. There are a few variables that trees must adapt their performance to.
Ferns tends to be . . . well, ‘ferny’, with divided or intricately lobed foliage. Staghorn ferns and bird’s-nest ferns are the more familiar of the rare exceptions. Staghorn ferns have two types of simple undivided fronds, and both types lack rachi. Bird’s-nest ferns have weirdly simple fronds that, although equipped with prominent rachi, lack any distinctive division or lobes that make ferns ‘ferny’.
The list of what ferns will not do is more noteworthy than the list of what they will do. They do not bloom with colorful or fragrant flowers. The do not produce fruit. Very few turn color in autumn, and their color is generally nothing to brag about. Most ferns will not maintain their appeal through drought, or if neglected too long. Nor will they tolerate heat and wind, especially in full sun exposure.
How Italian! Red, white and green! A coastal redwood with a white albino sport (mutant growth) amongst otherwise deep green foliage. Actually, it is very Californian. Coastal redwood is endemic to California with only a a few north of the border on the extreme southern coast of Oregon.
Severe summer weather is something that we think that we do not need to contend with. It only rarely gets as unbearably hot here as it does elsewhere, and when it does, it usually gets breezy by evening, and somewhat cooler overnight. Aridity, or the lack of humidity, is another advantage, at least for us. The plants in our gardens are affected by warm weather very differently than we are.
That refers to the pattern of the veins in the leaves. Long before studying horticulture and botany at Cal Poly, my classmates and I learned a bit about horticulture within the contexts of studying ‘nature’. While in the sixth grade, we all went to camp for a week. One of the many projects we did during that time was collecting a few leaves to represent three different vein patterns, and mounting them under clear plastic on a cardboard plaque. The three different patters were, ‘pinnate’, ‘palmate’, and ‘parallel’. I do not remember if we all used the same leaves, but for my plaque, I got a blue gum eucalyptus leaf to represent pinnate veins. Palmate veins were represented by English ivy. Parallel veins were represented by English plantain.
Staghorn ferns are epiphytes. They cling to tree trunks, rocks or whatever they happen to grab onto. They can root into decayed wood if it is porous enough, but they are satisfied to just cling to the exterior. They do not need soil. They sort of make their own soil by collecting debris that falls from the canopies of trees above. In the jungles where they live, they get all the water they need from rain. They often live in the crotches of branches because that is where they happen to land. (The epiphyte I wrote about earlier was just a palm that landed in the wrong place, but is not really an epiphyte. 
Tony Tomeo 