Colorado Blue Spruce

With such densely foliated low limbs reaching the ground, Colorado blue spruce functions as much as large shrubbery as a small tree.

Colorado and Utah share the same stately state tree; the Colorado blue spruce, Picea pungens, which is native to the Rocky Mountains between Arizona, New Mexico and southern Idaho. Colorado blue spruce are stoutly conical trees that grow slowly to eventually get more than seventy five feet tall. Where they need to compete with other trees in forests, the biggest are nearly twice as tall with trunks nearly five feet wide. However, because they grow so slowly, and do not get much bigger then they need to, well exposed trees stay proportionate to home gardens for many decades. Many shrubby compact cultivars actually stay less than ten feet tall. Foliage can be grayish green to silvery pale blue. The stiff and sharply pointed needles are about three quarters to an inch and a quarter long, and densely set on relatively rigid stems.

The elegant silvery blue foliage of the Colorado blue spruce is striking either in front of or behind darker evergreen foliage, like that of redwoods or junipers. These stout and densely foliated trees make any garden look a bit more woodsy.

Cork Oak

The bark actually looks like cork.

This is a tree that takes some time to impress. Bloom is uninteresting. Foliage is no more distinctive than that of coast live oak. Instead, the most spectacular characteristic of cork oak, Quercus suber, is the boldly striated and uniquely spongy texture of its mature bark. Such bark takes a few years to develop, but gets so thick that it seems significantly older.

As its name implies, cork oak had historically been the exclusive source of bark for corks and cork products. As modern and more practical materials diminished demand for such bark, cork oak became more popular as an evergreen shade tree. It is quite happy within the arid chaparral climates of California. In fact, it behaves much like native oak species.

Mature cork oak trees generally stay less than forty feet tall, even if their trunks are wider than three feet with their unusually thick bark. Without excessive irrigation, their roots are notably complaisant. Low branches are more visibly sculptural than high branches. With pruning for adequate clearance though, trees with high branches are striking street trees. Foliar and floral debris is quite messy during spring bloom.

Tanoak

Tanoak is rare within refined landscapes.

Its plump and inch-long acorns are misleading. Tanoak, Notholithocarpus densiflorus, is not actually an oak. Otherwise, it would be a species of Quercus. Regardless, its wood is potentially as practical for furniture and flooring as wood of other oaks. It also works very well as firewood. Historically, tanoak bark was useful for tanning leather, hence its name.

Although native and somewhat common in some coastal forests, tanoak is almost never a choice for intentional planting. Those that inhabit home gardens likely either grew from acorns, or were there prior to development of the landscapes. Young trees can grow fast to more than forty feet tall, typically with conical form. Mature trees might get twice as tall.

Tall trunks of tanoak are elegantly upright, and eventually develop lofty branch structure. Their gray or brownish bark is handsomely furrowed. The somewhat leathery evergreen foliage produces potentially objectionable tomentum. The dentate leaves are two to four inches long. Sadly, tanoak is very susceptible to Sudden Oak Death Syndrome (SODS).

Argyle Apple

Silvery foliage with fibrous brown bark.

Such silvery foliage provides a bold display on such a substantial tree. Most comparably silvery foliage is of smaller perennials or shrubbery, such as agaves or artemisias. Agyle apple, Eucalyptus cinerea, grows intimidatingly fast to nearly thirty feet tall and almost as wide. Although shorter than most other eucalypti, it can get a hundred feet tall in the wild. 

Paired juvenile leaves of young trees are circular and sessile (clinging directly to stems, without petioles). Unpaired adult leaves are lanceolate and as silvery as juvenile leaves. Coppicing or pollarding force juvenile growth and temporarily eliminate adult growth, but also ruin structural integrity. Trees subsequently rely on repetition of the same technique. 

Trunks and limbs can be disproportionately bulky, and create an illusion of a bigger tree. Irregular branch structure can be sculptural. Fibrous brown bark is handsomely furrowed. Juvenile foliage is a popular accessory to cut flowers. Adult foliage is likewise delightful. Incidentally, the Latin name of this species often transposes for Eucalyptus pulverulenta.

Palms Are Very Distinctive Among Trees

Palms provide distinctively lush foliar texture.

Palms seem to exemplify the culture of California. However, only the California fan palm, which is also the desert fan palm, is native. All others are exotic. With its dwarf palmetto, Oklahoma has as many native palms as California. Furthermore, the California fan palm is only endemic within remote riparian ecosystems of the Colorado and Mojave Deserts.

Common date palms were likely the first of the many exotic palms in California. Spanish Missionaries imported them for date production during the Eighteenth Century. Although initially utilitarian rather than decorative, recycled trees from displaced orchards became popular for larger landscapes. Potentially messy fruit is minimal without male pollinators. 

Long before urbanization displaced date orchards, many other palms came to California merely because of their visual appeal. Some are large enough to be shade trees. Others can provide shade in groups. Many develop elegant trunks or sculptural form. Some stay relatively low or shrubby. All innately provide famously and luxuriantly evergreen foliage.  

Palms are most certainly appealing within appropriate situations. They are very different from other trees though. Like arborescent yuccas and cordylines, palms are ‘herbaceous trees’. Unlike yuccas and cordylines, and with very few exceptions, palms do not branch. Nor do their trunks continue to expand in width as they continue to grow in height above.  

Palms consequently spend their first few years widening their bases at ground level. Big palms, such as Canary Island date palm, likely require many years. Once their bases are adequate, developing palms ‘launch’ into vertical growth. Although palms do not branch, a few, such as Mediterranean fan palm, develop multiple trunks from their primary bases. 

Once palms launch, they grow only upward. They lean only to avoid shade, or if pushed by wind. It is impossible to direct their bulky but singular terminal buds around obstacles, such as utility cables. It is also impossible to contain their shade as they get high enough to shade adjacent areas instead. Many palms are spiny, so are difficult to prune properly, even while young and within reach.

Red Ironbark Eucalyptus

The pendulous foliage of red ironbark eucalyptus moves softly in the breeze. The tall, curvy trunks are elegant and sculptural.

The many varied eucalypti never seem to outgrow the bad reputation of the blue gum and red gum eucalypti that get too big, messy and dangerous for urban gardens. Fortunately though, most others do not get nearly as large, and many stay proportionate to urban gardens. Their smaller canopies are neither as messy, nor as structurally unsound. Their adaptability to so many California climates and tolerance of aridity are serious advantages.

Red ironbark eucalyptus, Eucalyptus sideroxylon, is one of the mid-sized eucalypti that can eventually get quite tall, so is probably best where it has room to grow. Pruning for containment in compact gardens is actually quite a bit of work. Their coffee colored and deeply furrowed bark on elegantly sculptural trunks and limbs contrast nicely behind the mint frosting colored and softly pendulous foliage. The lanceolate leaves are about five inches long and three quarters of an inch wide. Flowers are almost always pinkish red, but can be pink or white.

Blue Spruce

Most blue spruce are garden varieties.

Sitka and Brewer spruce both live at low elevations and near the coast within their native ranges. Yet, neither perform as well here as blue spruce, Picea pungens, which is native to much higher inland regions of the Rocky Mountains. It grows neither as big nor as fast here as in the wild, so few old local trees are taller than thirty feet, or broader than twenty. 

Although compact, blue spruce should get sufficient space to develop its densely conical form without pruning for confinement or clearance. Such pruning is disfiguring. Since the evergreen canopy is so dense, it should retain low branches to the ground for as long as possible. Blue spruce works more like big and formal shrubbery than like compact trees.

Some cultivars of blue spruce are very stout and rounded. Most have remarkably blue or silvery color. Seed grown trees (which are not cultivars) are sometimes available online. They have potential to exhibit notable variation. Some might develop slightly more open canopies, with elegantly upwardly curved limbs. Spruce needles are about an inch long with quite a prickly texture.

Collect Fallen Leaves Before Winter

Fallen leaves can clog drainage.

The problem with all the colorful foliage that adorns so many of the deciduous trees in autumn is that it does not stay in the trees too long. Combined with all the other less colorful deciduous foliage, as well as whatever evergreen foliage happens to fall this time of year, it will become quite a mess by winter. Rainy and windy winter weather will only make it messier by bringing down even more foliage!

Contrary to popular belief, many evergreen trees are just as messy as deciduous trees are. Instead of dropping all their foliage in autumn or winter, most evergreens drop smaller volumes of foliage throughout the year. The mess is less obvious since it sneaks up slowly, but can accumulate over a few months. Only a few evergreen trees drop much of their foliage in more obvious seasonal phases.

Debris from evergreen trees is actually more likely to be a problem for plants below. Pines, cypresses, firs, spruces, cedars, eucalypti and many other evergreen trees produce natural herbicides that inhibit the emergence of seedlings of plants that would compete with them in the wild. In landscape situations, this unfortunately interferes with lawns, ground covers and annuals. Besides walnuts and deciduous oaks, not many deciduous trees use this tactic.

Regardless, any foliar debris can be a problem if allowed to accumulate too long. Large leaves, like those of sycamore, can accumulate and shade lawn, ground cover and some dense shrubbery, and can eventually cause mildew and rot. Finely textured foliage, like that of jacaranda or silk tree, can sift through most ground covers to the soil below, but can still make a mess on lawn.

Before rainy weather, debris should be cleaned from gutters and downspouts. Because some foliage continues to fall through winter, gutters will likely need to be cleaned again later. Flat roofs and awkward spots that collect debris, such as behind chimneys, should also be cleaned.

Gutters at the street are more visible and accessible, so do not often accumulate enough debris to be a problem, but may need to be cleaned if they become clogged with debris washed in by the earliest rains. Fallen leaves should be raked from pavement so that it does not get dangerously slippery, or stain concrete too much.

Fern Pine

Narrow leaves resemble pine needles.

It is neither a fern nor a pine. Fern pine, Podocarpus gracilior, can be a tree taller than fifty feet, and half as broad, but is often a shorn shrub or hedge that can be kept less than eight feet tall. Stems are limber enough while  young to be espaliered. The finely textured evergreen foliage is somewhat yellowish out in full sun, and darker green in partial shade. Individual leaves are as long as two and a half inches, and less than a quarter inch wide, and hang almost like fat pine needles. Some but not all mature trees can drop a bit of messy fruit with hard pits that are a bit larger than those of cherries. Bark gets distinctively blotched as it ages. The deep roots can be remarkably complaisant with concrete. Outer growth can get damaged by the harshest frosts every few winters or so, or roasted by hot dry heat every few summers.

Canary Island Pine

Canary Island pine displays fluffy foliage.

For spacious landscapes, Canary Island pine, Pinus canariensis, became more common than Monterey pine through the 1970s. New trees became less popular as old trees demonstrated how big they get! However, as seemingly docile live Christmas trees, they still often sneak into gardens that are not big enough for them. Their short blue juvenile needles suggest that they stay small.

They instead get quite tall. Old trees can get more than a hundred feet tall, even if their canopy gets no wider than twenty feet. Their rich brown bark is distinctively and coarsely textured. Their thin and long needles are somewhat pendulous, with a rather fluffy appearance. They are in bundles of three. Although individual trees are not very broad, their shade can get too dark for other plants.

Canary Island pine is a stately tree, but is not easy to accommodate. It produces copious foliar debris that can shade out lawn and ground cover, and accumulate on shrubbery. In unrefined areas, without other plants, foliar debris suppresses weeds. However, too much can be combustible. Such grand and resilient trees suit parks, and are ideal for freeway embankments and interchanges.