In the natural forest, trees sprout up from the humus of the forest floor and grow upwards to the light. Other trees succumb to old age, or fire or lightning strikes and eventually fall back to earth to become the fertiliser for other trees and vegetation. Life and death is the cycle of the forest.
And in our urban areas, the life cycle of trees continues unabated, though the cycle is strongly controlled by the hand of man. Trees are continually cut down for developments and roads and new trees are continually planted, sometimes just for their appearance rather than long-term sustainability.
Are there any guidelines that we might follow for ideal tree selection? Should we be thinking about much more than convenience and appearance when planting trees? I prefer the long-term path of sustainability, following the principles of permaculture where nature can take care of itself if we let it.
So let’s begin with what NOT to plant.
Eucalyptus
Though Eucalyptus has numerous medical and aesthetic values, it’s best left in its Australian homeland. I’ve researched extensively on the pros and cons of eucalyptus and there are many reasons to never plant more eucalyptus trees in your Southern California yards.
Eucalyptus trees suck up inordinate amounts of water, inhibit the growth of other vegetation under the trees and actually cause nearby soil to absorb less water. However, if you must cut one down, the hard wood is good for building projects (like fences) and firewood.
Others
In fact, depending on the area, certain non-native trees create more problems than they solve. Mexican fan palms, for example, widely planted in Southern California, are difficult to maintain and offer little tangible benefit to the local environment: no shade, no mulch that benefits the local soil and they become a shelter for pigeons and rats. Native palms would always be a better choice.
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Natives
Natives of any given area should be among your top choices. Here, where I live in Southern California, there are plenty of natives, which also produce beauty and provide food. Native cherries are evergreen and they produce delicious fruit. Toyon is another native evergreen tree whose little red fruits can be eaten, if you take the time to learn how to prepare them. Elder tree is a deciduous tree that requires a bit more maintenance, but does produce edible and medicinal flowers and fruit.
If you live in a dry and hot enough area, you should consider trees such as palo verde, mesquite and jojoba as yard trees, which also produce something edible.
But whatever you choose, begin by choosing the trees that are native to your area, since those trees are most ideally suited to that region and are most likely to live a long trouble-free life without lots of human interference.
Drought Tolerance
As we proceed into the future with plans for how to green-up the landscape, we cannot escape the fact that trees need care, especially in the initial stages. It behoves the planner to look at those trees that do well on their own, with limited water and limited care. This usually – but not always – suggests natives be used.
Natives live where they live because the conditions are most conducive to their pattern of life. Otherwise, they would not have survived where they are in the wild, with little or no human intervention. They may or may not be deciduous, but they are survivors.
In Southern California, there are old cabin sites in the mountains where people built homesteads a 100 or so years ago. Some of the trees and bushes they planted are still alive, which suggests that those early plants will survive drought and minimal care.
Some of the trees that I have noted in these circumstances include all the natives, of course. The non-native survivors include figs, olives, mulberries, various grape vines and citrus trees. All of these would be good choices for the modern urban planner who wants useful plants that require minimal care.
I have also seen that the oleander bush survives with no care, but because it is so toxic, it would be better not to plant oleanders as part of the urban landscape.
Evergreen Vs. Deciduous
Landscapers are often the ones who have promoted particular trees for their beauty or convenience. They are the ones who’ve given us so many of the poisonous oleanders throughout Southern California. To be fair, the evergreen oleander requires so little maintenance that it is no wonder you see it along so many freeways. But if you have limited space and you want a productive yard, you would be wise not to choose an oleander.
For you non-gardeners, evergreens are those trees and bushes that never go bare and always have some leaves, year-round. Deciduous means that they drop their leaves in the winter and go bare. In some situations, a deciduous tree is a good choice in front of a south-facing window, so that it’s shady in summer, but the sun is allowed into the home in winter when desired.
Although a deciduous tree means that you might have to ‘clean-up’ the fallen leaves, you should also consider the possibility of just letting the leaves lay there. After all, in the forest, the dropped and decaying leaves are what provides ‘food’ for the trees, season after season.
Fruiting Or Not
Yard spaces vary as do everyone’s needs. After I’ve selected natives for my yard, the next consideration is whether or not I want to grow some of my own food there. Quite a few good choices are available for Southern California and you should begin by making a list of those foods you enjoy eating. Then, cross off the ones that don’t grow well here in Southern California. My short list for this area includes avocadoes (each variety has different fruiting patterns), apples (Anna and Beverly Hills do well here), Santa Rosa plum, all citrus, figs and loquats.
Local Considerations
Regardless of where you live, there are local weather patterns and wind patterns that can affect the trees that you grow on your property. Before purchasing and planting new trees, you should consider the lay of your land, wind patterns, sun exposure, soil type and perhaps dominant trees in the area. If you’re like me, you’ll want to plant for the long term, to create a mini-environment, which creates a pleasant living condition, is easy to care for and produces food and fragrance for everyone living there.
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A Study For Future Trees
The University of California Cooperative Extension (UCCE) has partnered with the U.S. Forest Service to undergo a 20-year study to determine which trees would be best for California’s urban area. The research study was prompted due to the changing climate of California, which means less rain, higher temperatures and therefore more stress on the trees of the urban landscape.
“The idea is to look at available but under-planted, drought-tolerant, structurally sound, pest resistant trees for Southern California that do well in even warmer climates,” said Janet Hartin, UCCE horticulture advisor in San Bernardino County.
The collaborative expects to publish the first of their results by the end of 2019, attempting to share what trees might be the best to plant in the future. The focus was upon trees that were already available in nurseries, but were not already widely planted.
They looked for trees that have a good degree of drought tolerance and disease resistance, plus produce minimal leaf litter. The researchers also sought trees that would provide ample cooling shade ideally for at least 50 years.
“Urban areas create heat islands, with dark asphalt surfaces reradiating heat. Cities can be 10 to 20 degrees warmer than the surrounding environment,” Hartin said. The planting of appropriate trees improves not just the beauty of an area, but oxygen availability, soil health and stability and wildlife habitat.
Some of the trees that will be studied for their future potential are acacia and mulga (from Australia), the blue palo verde and desert willow (both native to southwest U.S.), Brazilian cedarwood (native to Brazil), Catalina cherry, netleaf hackberry and island oak (all California natives).
Partners in the tree study are Los Angeles Beautification Team volunteers, the LA Parks and Recreation team, the Chino Basin Water Conservation District and Mountain States Wholesale Nursery.
Coda
The planting of trees creates eco-systems and can improve or degrade the landscape, depending on several important factors that the urban planner should consider:
• The selection of the tree should be based on long-term considerations. Native trees to a given area will always do better than exotics, in part because they will require less work to maintain and less water.
• Deciduous trees can contribute leaf mulch and open up with more light in the winter, so it isn’t always necessary to choose evergreens.
• Trees that produce edible nuts or fruits should definitely be a part of the selection process, as long as there is a long-term plan for collecting, using or distributing the product of the tree.
• Strongly aromatic trees should definitely be considered for their ability to enhance the urban landscape.
Christopher Nyerges teaches sustainability and self-reliance in the urban setting. He is the author of Self-Sufficient Home, Extreme Simplicity: Homesteading in the City, and other books on ethnobotany and survival. He can be reached at www.SchoolofSelf-Reliance.com.
ALL PHOTOS: CHRISTOPHER NYERGES
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