Autumn Foliage In Mild Climates

Minor chill initiates autumn foliar color.

Colorful foliage is always present. After all, green is a color, even without any other color or variegation. Defoliation of deciduous foliage during autumn reveals evergreen foliage beyond, even if fading through winter. Immediately prior to defoliation though, deciduous foliage of quite a few species temporarily becomes spectacularly colorful autumn foliage.

Whether deciduous or evergreen, foliage that is most colorful during spring and summer contains chlorophyll. Regardless of how variegated, reddish, purplish, yellowish or other color it might be, it is also green to some degree. It could not be photosynthetically active otherwise. Colorful autumn foliage exhibits brighter color as its chlorophyll decomposes.

Autumn foliage is most spectacular where it is native, such as New England. Much more of it inhabits forests than home gardens. It is not spectacular within forests here because only a few sparsely dispersed native species produce impressive foliar color for autumn. Its naturally local scarcity likely contributes to its limited popularity within home gardens.

Locally mild weather also limits the popularity as well as the potential of autumn foliage. Many of the most colorful maples of New England merely turn blandly pallid yellow prior to hastily premature defoliation here. However, several other species develop exemplary foliar color in response to minor chill, and seem to be as happy here as in New England.

Chinese pistache, sweetgum, flowering pear and ginkgo are four trees that most reliably provide autumn foliage here. Crape myrtle is a smaller tree that is almost as reliable, and blooms splendidly for summer. Persimmon gets as colorful as Chinese pistache, with an abundance of fruit. Boston ivy is a vine with color that is comparable to that of sweetgum.

Of course, even the most appealing of plants are not perfect. Their innate characteristics are relevant to selection. For examples, trees occupy significant space. Ginkgo becomes bright yellow, but without any other color. Sweetgum produces obnoxiously prickly fruits. Flowering pear is susceptible to fireblight. Boston ivy clings to surfaces and ruins siding, paint and fences.

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Sweetgum

Sweetgum colors with minimal chill.

The excellent and remarkably brilliant shades of yellow, orange, red and burgundy of the foliage in autumn suggest that sweetgum, Liquidambar styraciflua, is from New England. However, it is native between New Jersey, Florida and the eastern edge of Texas, as well as isolated forests of Central America. It actually prefers mild climates to where winters are too cold. Mature trees are generally columnar (relatively narrow) and less than fifty feet tall where well exposed, but can get more than twice as tall to compete in forests.

Unfortunately, mature sweetgum trees can be somewhat problematic in urban gardens. Limbs are often weak enough to break in wind, or if they get too heavy from the weight of their own foliage. Also, the abundant round seed pods are outfitted with nasty spikes, like little maces almost two inches wide. They are painful to step on, and can actually be quite hazardous.

Autumn Foliar Color Begins In October

After blooming so colorfully for summer, crape myrtle foliage turns bright orange and red for autumn.

Why do so many from other regions comment on the mild climates of the west coast of California as if pleasant weather is a deficiency? If horrid summer heat and frigid winter cold were worth bragging about, not so many people would have been so eager to migrate here.

Contrary to popular belief, the four seasons, although considerably milder than in other regions, are enough to keep our gardens productive, dynamic and even colorful in all seasons. All sorts of deciduous plants and fruit trees get just enough chill in winter to bloom reliably in spring. The warming weather between winter and summer that gets most plants to bloom is what spring is all about. Summer is then warm enough for fruit and vegetables to develop. Then there is autumn, when so many deciduous plants turn flashy colors before winter dormancy.

Although the mild weather limits the choices, there are still a few plants to provide autumn foliar color. Actually, autumn is not so colorful locally primarily because the potential for color is not exploited like it is elsewhere. There are just so many other plants that do not turn color in autumn to choose from. Really, Vermont would be less colorful if palm trees grew there!

Sweetgum, Chinese pistache, flowering pear and maidenhair tree are the most reliable trees for autumn color. Maidenhair tree turns remarkably bright yellow. The others get the whole range from yellow to orange to red. Sweetgum also gets burgundy, and has the added advantage of holding foliage until it gets knocked off by wind or rain. Where the big, bright orange (and yummy) fruit that hangs through winter is desirable, Japanese persimmon is as colorful as Chinese pistache. (Persimmons are horribly messy if not harvested.) Various poplars, tulip tree and black walnut can almost get as bright yellow as maidenhair tree.

Crape myrtle and redbud are shrubby plants that provide good autumn color. Redbud turns clear yellow. Crape myrtle though, can also get bright orange and brownish red. Several of the Japanese maples, although not always as reliable, can actually get even more colorful if the weather is right. Boston ivy (which is actually related to grape) is the most colorful of climbing vines, but because it attaches directly to whatever it climbs, it is best on concrete walls that it will not damage.

Maidenhair Tree

Maidenhair tree leaves look rather ‘fishy’.

There are not many trees that are as reliable for strikingly bright and clear yellow autumn foliar color as the maidenhair tree, Gingko biloba, is, even in mild coastal climates. The distinctive leaves flare out like fish tails, each with a prominent cleft that divides it into two wide lobes. (The species name ‘biloba’ means ‘two lobed’.) Some cultivars lack foliar clefts, have narrower leaves, or even develop milder yellow color in autumn. Those developed for home gardens exhibit relatively symmetrical branch structure, and are exclusively male, so can not produce the stinky fruit that some older female trees drop. (Trees grown from seed can be either male or female. Female cultivars are grown for fruit production and bonsai.) Some ancient trees in Japan, Korea and China are more than a hundred feet tall. Fortunately, maidenhair tree grows slowly enough to stay proportionate to compact urban gardens for many decades.

Maidenhair trees develop the best yellow fall color.

Chinese Pistache

Chinese pistache colors with minimal chill.

Those who crave fall color in mild climates should appreciate Chinese pistache, Pistacia chinensis. It is happy to provide fiery yellow, orange and red color in response to a slight chill. Actually, it retains its colorful foliage later into the season with mild chill than it does with frosty weather. Rain eventually dislodges all of its deciduous foliage through winter.

Because it is so resilient to harsh situations, Chinese pistache is popular as a street tree. Pruning is necessary to establish adequate clearance of broad limbs over roadways and sidewalks. Since roots can be shallow with regular watering, root barriers should protect nearby pavement. However, established trees do not need regular watering, if any at all.

Old Chinese pistache trees, as well as those that grow wild from seed, are either male or female. Female trees produce tiny but annoyingly abundant fruit. Modern cultivars are all male, and therefore fruitless. They may get more than forty feet tall, with broad canopies. The pinnately compound leaves are just about eight inches long.

Fall Color To Fall For

Fall color develops with seasonal changes.

Autumn is also fall here. Actually, ‘fall’ is the more popular name. It had been the popular name in England during the Sixteenth Century. The (generally) French name of ‘autumn’ became more common there during the Seventeenth Century. Yet, both names remained in use in the American Colonies. That is why autumn foliar color is more simply fall color. 

The natural fall color in New England, the Appalachian Mountains, the Rocky Mountains and the Great North Woods is famously exquisite. So many of the native deciduous trees develop remarkable fall color in response to local weather conditions. These same trees might not get sufficient chill to develop comparable fall color in milder climates of Florida. 

In most regions of California, natural fall color is limited by the ability of native species to develop such color. Bigleaf maple and the various poplars turn bright yellow with a slight chill, but are not abundant. Even when chilled, the foliage of most other native deciduous trees simply shrivels and falls without much color. Most of the native trees are evergreen. 

Therefore, most of the best local fall color is provided by exotic (nonnative) tree species. Such trees not only develop remarkable fall color, but do so in response to minimal chill. Sweetgum, flowering pear, Chinese pistache and ginkgo are four trees that most reliably develop brilliant fall color where winter weather is mild. None are native. All are popular.

Ginkgo turns brilliant yellow. The other three display various colors that range from bright yellow, to fiery orange, to rich red and burgundy. Their colorful foliage lingers longer than that of other deciduous trees. Sweetgum and flowering pear might retain fall color until it succumbs to rain in winter. Of course, these are not the only options for reliable fall color. 

No tree is perfect. Although very colorful in autumn, sweetgum is notoriously structurally deficient, and produces obnoxiously spiked fruiting structures. Flowering pear is innately susceptible to fire blight. All deciduous trees drop leaves, which need raking. Trees must conform to their situational limitations, as well as their particular landscape applications.

Boston Ivy

Boston ivy gets colorful before autumn.

It is the ‘ivy’ of ivy league schools. Nonetheless, Boston ivy, Parthenocissus tricuspidata, is neither an ivy, nor indigenous to Boston. It is from eastern Asia, and is related to grape vines. It is related to Virginia creeper too, which is actually native to Boston, Virginia and the eastern half of North America. It has become popular locally for freeway sound walls. 

Boston ivy is an aggressive clinging vine that can climb to the top of a ten story building. Unfortunately, there are a few problems with that. It ruins wooden or painted surfaces, so can only climb concrete or masonry. It climbs over windows if it gets the chance. Thicket growth is difficult to remove if it is too high to reach. On rare occasion, mice can nest in it. 

Otherwise, Boston ivy works well on freeways. Although deciduous, its vines discourage graffiti. Even while bare, its texture helps to muffle sound. Its exquisite autumn foliar color might begin to develop as early as late summer, and lingers until frost. Boston ivy is quite resilient to neglect. Shabby plants generate fresh new growth after major winter pruning.

Flowering Dogwood

Bloom like this waits for spring.

Flowering dogwood, Cornus florida has something in common with Poinsettia. The most colorful component of their bloom is not floral, but is instead foliar. What appears to be petals are colorful leaves known as bracts. Exactly four bracts surround each small cluster of tiny and unimpressive pale green real flowers. These bracts are most popularly white, but can be pink or rarely brick red.

The deciduous trees are bare now, but bloom spectacularly in early spring. Any necessary pruning should happen after bloom, and preferable after new foliage matures somewhat. Floral buds for next year are already prominent on the tips of bare twigs. Dormant pruning would eliminate some of the buds prior to bloom. For now, only minor grooming of unbudded interior growth is practical.

Mature flowering dogwood trees can be twenty feet tall, but typically stay lower. As understory trees, they prefer a bit of shelter from larger trees. Foliage can scorch if too exposed. Some cultivars have variegated foliage. All can develop vibrant orange and red foliar color for autumn, even with minimal chill. Floral debris resembles fallen leaves that fall just as new and real foliage develops.

Chrysanthemum

Chrysanthemums are just right for autumn.

Mild autumns and arid summers keep chrysanthemums on a different schedule here than in most other regions. They can get planted in spring to grow through summer and bloom through autumn; but because they can take a bit of work, they are more often planted while blooming in autumn. Although commonly grown as autumn annuals, they are perennials that can regenerate next spring, grow through summer, and bloom even better the following autumn.

Centuries of development in Japan have produced more varieties of chrysanthemums than can be documented. There are really some weird types grown for cut flowers or by hobbyists. Garden varieties are mostly limited to simpler flowers that do not need much thinning or staking. Color ranges through all sorts of hues and shades of yellow, orange, red, pink and bronze, as well as a few purplish colors, cream and white. Many have yellow centers. The aromatic foliage is alluring to some, but objectionable to others.

Autumn Color From Deciduous Foliage

Deciduous foliage can get delightfully colorful.

Autumn does not get cool enough locally to prevent everything from blooming. A few plants can bloom sporadically all year except only during the coolest part of winter. A few plants naturally bloom in autumn. Cool season annuals begin blooming before warm season annuals finish. Flowers can potentially provide plenty of autumn color if necessary. A mild climate can be a major advantage.

It can also be a disadvantage. Minimal chill causes deciduous foliage to start to get messy before it starts to get colorful. Some deciduous plants shed completely before getting chilled enough to develop appealing autumn color. A few others do not even get cool enough to defoliate completely. They instead retain their shabby old foliage through winter until new foliage replaces it in spring.

Nonetheless, several adaptable deciduous plants get sufficient chill to develop impressive autumn color here.

Sweetgum, Chinese pistache, flowering pear and ginkgo are likely the four best deciduous trees for autumn color locally. Sweetgum and Chinese pistache produce the most impressive ranges of vibrant colors. Flowering pear is comparable, but with less yellow, and more rich deep burgundy red. Ginkgo lacks such range of color, but develops the brightest and clearest yellow autumn color.

Boston ivy, crape myrtle and persimmon get about as colorful as sweetgum, even if incidentally to their primary duties. Crape myrtle is popular for its abundant and richly colorful bloom in summer. Persimmon is a fruit tree. Boston ivy obscures graffiti and helps muffle sound on freeway soundwalls. Cottonwood and black walnut turn bright yellow, but in the wild rather than in refined gardens.

Even for the locally mild climate, there are plenty of deciduous plants that provide foliar autumn color. Trees are the most familiar. Vines and shrubbery are also popular. Because this mild climate is marginal for some of them, color is likely to be variable from year to year. Unfortunately, some that perform satisfactorily for inland locations may perform less satisfactorily in coastal conditions.