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Six on Saturday: Eucalyptus

Blue gum earned a bad reputation for all species of the genus decades ago. It really is as massive, messy, combustible, unstable and structurally deficient as reputed. Some find its foliar aroma to be objectionable. Fortunately, it is not as invasive as formerly alleged. It is common only because it was planted so extensively a long time ago, and is somewhat naturalized in some regions.

Other eucalypti are more appropriate to landscape situations than blue gum, which is #6 below. #3 and many others are now classified as Corymbia, rather than Eucalyptus. Genus is omitted for these Six.

1. pulverulenta or cinerea is the only eucalyptus that was here when I arrived. I learned this species as ‘cinerea’. However, the correct designation seems to be ‘pulverulenta’. #2 should match.

2. cinerea or pulverulenta, as mentioned above, was supposed to match #1. It was labeled as cinerea. I thought that #1 is cinerea. I still do not know which is cinerea and which is pulverulenta.

3. sideroxylon is the first tree I planted in 2021. For such a dinky tree, it already has quite a history. I gave it to my colleague who appreciates the distinctively dark and coarsely textured bark.

4. citriodora is as goofy as it looks. It is about fifteen feet tall, with just a few leaves at the very top. Its smooth white bark contrasts with that of #3, which it will be planted close to this winter.

5. globulus ‘Compacta’ gets coppiced to produce aromatic juvenile foliage, but is less aromatic than the straight species, #6. It might be my least favorite eucalyptus, although I am fond of #6.

6. globulus gets pollarded to produce aromatic juvenile foliage, like #5, but on a trunk. It is the eucalyptus that gives all other eucalyptus a bad reputation. Nonetheless, I like its grand stature.

This is the link for Six on Saturday, for anyone else who would like to participate:

https://thepropagatorblog.wordpress.com/2017/09/18/six-on-saturday-a-participant-guide/

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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.

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Chinese Elm

Intricately blotched bark distinguishes Chinese elm.

Since the Dutch Elm Disease (DED) epidemic that killed so many old and stately American elm trees so many years ago, the old fashioned Chinese elm, Ulmus parvifolia, has been unavailable in nurseries. That is why there are only old and middle aged trees, and maybe a few feral seed grown trees. Chinese elm is not bothered much by the disease, but is a vector. ‘Drake’ is a modern DED resistant cultivar, but it has a very different personality, with a more upright and symmetrical structure.

The elegantly lanky trunk and main limbs can be quite curvacious, with distinctively blotched gray and tan bark. The deciduous foliage can be messy in autumn as it falls slowly and may linger through December. The neatly serrate leaves are only about an inch or two long, and half as wide. Mature trees can be more than fifty feet tall.

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California Buckeye

California buckeye resembles related horse chestnut.

Chaparral climates are not easy without irrigation. The long summers are warm and arid. California buckeye, Aesculus californica, knows what to do if it can not stay hydrated out in the wild. It simply defoliates. Yes, it goes bare right in the middle of summer. If it does it early enough, it refoliates after rain resumes in autumn, only to defoliate again for winter.

This ‘twice deciduous’ characteristic is likely why California buckeye is not more popular for unirrigated landscapes of other natives. Shade is an asset through warm summers. In coastal, riparian or irrigated landscapes, the original spring foliage lasts through summer to defoliate in autumn, like that of most other deciduous plants. It may get shabby though. 

Nonetheless, California buckeye is a delightful small tree, typically with a broad and low canopy suspended by a sculptural branch structure. Not many get more than twenty feet tall, although some get twice as tall. Bark is strikingly pallid gray. The elegant leaves are palmately compound. Six inch long trusses of tiny white flowers are sweetly fragrant in spring.

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Sunlight Is Becoming A Commodity

Sunlight has not changed. Architecture did.

Shade trees are no longer appreciated like they had been. Only half a century ago, they were important components of suburban landscapes. Big deciduous trees shaded broad lawns and sprawling roofs during the warmth of summer. They defoliated to let warming sunlight through during winter. Now, modern architecture would not accommodate them.

Sunlight has not changed. Human interaction with it has. Modern homes are significantly taller, so create bigger shadows. They are closer together, with less garden space that is not within their bigger shadows, or shadows of adjacent homes. Higher fences intended to compensate for the minimal proximity of adjacent homes contribute even more shade.

Gardening can be difficult within the limited space and abundant shade of modern home gardens. Small evergreen trees or big shrubs that obscure unwanted scenery above the fences can also obscure much of the sunlight that manages to get past the infrastructure. Substantial vegetation in neighboring gardens can get close enough to be influential too. 

The primary part of modern homes that is not excessively shaded is the roof, which is not used for gardening. Trees that are proportionate to modern home gardens are not much taller than associated modern roofs. Modern attics are fortunately insulated so efficiently that shade is not important. Besides, many modern homes are outfitted with solar panels. 

Walls and windows of modern homes are efficiently insulated as well. Warming sunlight during winter is therefore not as much of an advantage as it is for older homes, although it is appealing within sunnier homes. Ironically, the utility cables of many modern homes are subterranean, so will not interfere with trees that get too big for their confined spaces. 

Regardless of their functions within their landscapes, even small trees can develop roots that are sufficiently aggressive to displace pavement and deck suspensions, particularly since they are likely to be close to them where space is limited. Turf grass that is thin and wimpy because of insufficient sunlight is more susceptible to lumpiness of surface roots. Because of proximity, neighboring gardens must be considered too.

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Box Elder

Box elder is the ‘other’ maple.

No other maple is native to so much of North America as the common box elder, Acer negundo. Yet, because of innate structural deficiency and a general lack of pizazz, it is also one of the least popular. The smaller and more adaptable garden varieties are more often grown for their interestingly colorful foliage. ‘Flamingo’ starts out with pink, white and pale green foliage that turns richer green and white by summer. ‘Violaceum’ has smokey purplish new foliage that fades to rich green. ‘Auratum’ has yellowish foliage that fades to chartreuse green. Any stems that try to revert to a more natural shade of green should be removed before they dominate. Unlike other maples that have distinctively palmate leaves, box elder has compound leaves with three or more leaflets each.

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Black Locust

White black locust bloom seems oxymoronic.

The natural ranges of black locust, Robinia pseudoacacia, likely included only the Ozark Mountains, the Ouachita Mountains, and the Appalachian Mountains south of New York. Early American colonists planted it elsewhere before botanists documented its origins. It was notably used for firewood, durable lumber, erosion mitigation, and soil conditioning.

Modern cultivars are less useful for such applications, but are more appropriate for home gardens. Regardless of elegantly lofty form, delightfully finely textured foliage, and richly fragrant white bloom, the species is aggressively invasive and wickedly thorny. Cultivars can bloom pink or rosy pink, lack thorns, and develop more compact and shapely forms.

Bloom resembles that of wisteria, with many small flowers hanging in pendulous trusses. Deciduous foliage, which was absent through winter, appears in conjunction with bloom, but does not obscure it. Individual leaves are pinnately compound, with small leaflets on central rachises (stalks). Most modern cultivars will not get much more than forty feet tall, to make moderate shade.

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Limb Failure Of Spontaneous Nature

Riparian trees notoriously shed limbs spontaneously.

Winter storms sometimes break limbs or topple trees. Such damage is no surprise during winter because that is when almost all windy weather happens here. Early storms during autumn might be more damaging because deciduous trees are less aerodynamic prior to defoliation. Nonetheless, falling trees and limb failure are typically associated with wind.

That is why spontaneous limb failure is such a surprise when it happens, typically during pleasantly mild or warm weather of spring or early summer. It is more likely without wind than with it. Humidity, although atypical here, is a contributing factor. Healthy trees within riparian situations or lawns are more susceptible than distressed trees in drier situations. 

Particular types of trees are more susceptible to spontaneous limb failure as well. Valley oak, coast live oak, sweetgum, carob, some pines and various eucalypti may shed limbs after an unusually rainy winter or an increase of irrigation. Riparian trees, such as willow, cottonwood, box elder and sycamore are notorious for shedding big limbs unexpectedly.

Spontaneous limb failure occurs if limbs are unable to support their own increasing foliar weight. Bloom can add significant weight too. Warmth promotes the vascular activity that increases foliar weight. Humidity and insufficient air circulation inhibit evapotranspiration (evaporation of foliar moisture), which typically compensates for increasing foliar weight.

As the terminology implies, spontaneous limb failure occurs suddenly, and often without warning. It is therefore potentially very dangerous. It is common among limbs that exhibit no prior structural deficiency. Even experienced and educated arborists who are familiar with vulnerable tree species can not identify and mitigate all potentially hazardous limbs. 

Arborists often suggest pruning to limit the weight of trees that are innately susceptible to spontaneous limb failure. However, limbs that are already sagging from their own weight are risky to engage. Most damage occurs in spring and early summer. Fruit trees that are too productive can succumb to the weight of fruit as it ripens through summer or autumn.

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Junipers Should Get More Consideration

Old junipers still work like new.

Too much of a good thing eventually gets old. That is how so many of the good junipers that were so popular half a century ago became so unpopular. They became too common, and many were planted into situations that they were not appropriate for. As they matured, many became overgrown or disfigured. Only recently have a few newly introduced modern cultivars restored the appeal of both new and traditional junipers to a generation that is less familiar with their former stigma.

Even though all junipers are evergreen and somewhat similar in regard to foliar texture and their lack of interesting bloom, they demonstrate considerable diversity. Some are low and sprawling ground covers. Others are dense low shrubbery. A few develop as small trees. Branch structure may be densely compact, gracefully arching, rigidly upright, or sculpturally irregular.

Some junipers have yellowish new growth that eventually turns to a more typical deep green. Others are bluish gray throughout. A few rare types are variegated. Almost all junipers have scale-like leaves (like those of cypress). A few have needle-like leaves.

‘Blue Arrow’ and more traditional ‘Skyrocket’ junipers are like short and plump Italian cypress with bluish or gray foliage. ‘Wichita Blue’ juniper is even shorter and plumper, with more sculptural branch structure. However, it is not nearly as irregular and sculptural as the old fashioned ‘Hollywood’ juniper. Modern ‘Gold Star’ and the older ‘Old Gold’ junipers are shrubby types that exhibit arching stems with gold tips.

‘Icee Blue’ is like an improved version of the classic ‘Blue Rug’ juniper, that matures as a shallow bluish ground cover. ‘Blueberry Delight’ juniper is one of the few junipers known for conspicuous fruit, with pretty powdery blue berries against grayish needle-like foliage on trailing stems. ‘Limeglow’ juniper gets a bit deeper, and exhibits chartreuse new growth that turns rich green.

Just because junipers can be shorn certainly does not mean that they should be! Shearing deprives junipers of their naturally appealing texture and form. Instead, junipers should be selectively pruned only where necessary to eliminate growth that is beginning to become obtrusive. Stems should be cut back deeply into the main stems from which they originate, in order to avoid leaving stubs or disfigured stems. Tree junipers like ‘Hollywood’ juniper, as well as overgrown shrubby junipers, can be pruned to expose bare trunks and stems. The gnarly stems and shredding bark can be as appealing as the foliage that obscures them.

Otherwise, once established, junipers do not need much attention or water, and are remarkably resilient. They only rarely get infested with spider mites or scale insects, or get damaged by disease. They only want good sun exposure.

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Flowering Peach

Flowering peach flowers produce no fruit.

Since it does not produce an abundance of cumbersome fruit, flowering peach, Prunus persica, does not need the aggressive pruning while dormant through winter that fruiting peach requires, and can get significantly larger. However, tip pruning after bloom instead promotes shrubbier growth that blooms more prolifically the following spring. The fluffy double flowers are clear white, bright pink or rich pinkish red. ‘Peppermint’ flowering peach has red and white flowers, with a few flowers that are only white, and sometimes a few that are only red.