The deeply colored foliage of black mondo grass, Ophiopogon planiscapus ‘Nigrescens’, is about as convincingly ‘black’ as foliage can get. It is darker than bronze New Zealand flax, purple leaf plum or bronze coral bells. Only purple beech or chocolate coleus are comparable. The foliage is dark enough to contrast very well against lightly colored planters or gray concrete, so works well in urns or mixed perennials, and bordering walkways. If it gets enough sunlight, black mondo grass makes a nice small scale ground cover under Japanese maples.
Mature plants stand only about half a foot tall, and spread slowly. The happiest plants can get nearly twice as tall. The softly cascading leaves are only about a quarter inch wide. Small spikes of tiny pink flowers that sometimes bloom in summer would contrast nicely against the dark foliage, but are rarely seen above the foliage. Black mondo grass prefers rather rich soil and somewhat regular watering. However, as they disperse roots, older plants do not seem to mind too much if they briefly get a bit dry.
Sweetgum, flowering pear and Chinese pistache are the most reliable trees for flashy autumn foliar color, especially in such mild climates. They may not seem like it this year though. After a late start, only sweetgum is coloring well. Flowering pear trees that are beginning to show color farther inland seem to lack their typical bright yellow and orange, and are showing more dark rusty red.
Like so many flowers that bloom in spring, foliar color in autumn is as variable as the weather. Temperature and humidity can either inhibit or enhance color. It is impossible to say what caused the disappointing color so far, or if foliage that colors later will be just as bland. A sudden chill could change things for Chinese pistache that are still behind schedule.
Maidenhair tree (gingko) is the best for bright yellow, but lacks any other color. Fruitless mulberry, tulip tree and various poplars can be nearly as bright yellow in a good season, and may still color well. Of the various willows, only a few color well, and they tend to be more sensitive to weather. Early rain can rot their leaves before they get much color at all.
Although elms are not known for coloring, some of the modern varieties turn remarkably bright orange. However, the few oaks that color well in colder climates turn only dingy brown locally. The few North American maples that can provide color do not hold their colored foliage very long. All sorts of trees have all sorts of personalities.
Eastern redbud, smoke tree and crape myrtle are shrubs or small trees that color as well as larger trees in autumn. Crape myrtle can be as bright yellow, orange and red as sweetgum. Some Japanese maples color better than others, and some can be quite impressive, but only if their foliage does not get roasted by warm and arid weather through summer.
Where it can be accommodated, Boston ivy is an aggressively clinging vine that provides all the remarkably colorful foliage on freeway sound-walls. It is out on the freeways for a reason though. It can ruin any other surface that it clings to.