One of a plant lover’s greatest pleasures is discovering a species that thrives in a place where it has no business growing, at least according to accepted wisdom regarding that species’ growth requirements. I think this may be a reflection of the rebelliousness that characterizes plant lovers and growers as a group. If we are told that a certain plant cannot grow in a certain place because of an inhospitable climate, for example, we immediately start figuring out a way that, nevertheless, this plant could grow there. Entire agricultural industries based on what were considered exotic tree crops for California at the time – including avocado, date, and pistachio – were founded by individuals who defied skeptics in planting certain trees where no one believed they could grow.

It was thus with distinct pleasure that I received a communication from Jeff Ashley in Studio City regarding an unusual tree, for this part of the world, that is thriving in his front yard. It is a red oak (Quercus rubra) nearly 50 feet tall and 50 feet wide with a trunk diameter of two and a half feet. It is at least 75 years old and could be older. I had never seen a red oak in Southern California before. Its habitat is the East, the Midwest, and the Southeast, and we can only speculate as to how this tree ended up in Ashley’s front yard.

I wonder if local nurseries in the 1940s and 1950s grew trees from the East and Midwest, which is where many Studio City residents of the time had probably previously lived. Perhaps they wanted to grow red oaks on account of the brilliant scarlet fall foliage that they remembered from back home. Alas, Ashley informed me that his tree’s foliage, while turning gold, does not display the red color from which it gets its name.

This might also explain why more red oaks were not planted; once they failed in the fall color department, perhaps people decided to plant other trees instead. Although shortening days are a signal for leaves of many deciduous trees such as red oak to change color, fall temperatures (ours are too warm) and soil pH (ours is too alkaline) are also critical factors in foliar color change where deciduous oaks are concerned.

It might also have been the case, however, that other red oaks that were planted simply did not survive the dry Southern California climate. Ashley speculates with good reason that the microclimate enjoyed by his red oak has contributed significantly to its robust growth. Immediately to the west of his tree, a towering liquidambar tree is growing in the parkway, while a California sycamore of immense size is flourishing just across the street. These trees clearly provide protection from the harsh afternoon sun and take the edge off the dry heat foreign to the red oak’s habitat.

We can learn a lesson from Ashley’s red oak about the importance of microclimate, especially in these droughty times. Shade or just protection from afternoon sun can do wonders when it comes to coping with drought since it will reduce water loss from leaves of nearby plants and from the soil in which they grow. A side benefit of trees is their leaves, which can be piled as high as four inches to bring soil water loss to a bare minimum and keep roots cool.

Incidentally, one of the most desirable Studio City streets from the standpoint of arboreal beauty is Cantura Street, one block south of Ventura Boulevard. Both sides of the street are lined with California sycamores. Are there unusual or memorable trees in your past or present? If so, you are invited to write to me about them.

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If you are looking for trees that do change color, there is a variety from which to choose even if, as luck would have it, each of them is somewhat problematic.

Liquidambar (Liquidambar styraciflua) foliage turns the classic gold, orange, red, and burgundy that we associate with fall color but, as it ages, its surface root system makes it impossible to grow anything in its vicinity.

Chinese tallow tree (Sapium sebiferum), of moderate size, has striking, unparalleled iridescent foliage in the colors noted above but, alas, is shapeless when mature and produces slippery, hazardous fruits. In its early years, however, there is no more exquisite tree to have around for fall color. Chinese pistache (Pistacia chinensis) may have the most brilliant orange and scarlet fall color of any tree. Its berries, however, are messy, staining sidewalks, and if you give it too much water it will die from Verticillium fungus that enters and clogs its roots. However, Chinese pistache is an excellent selection for a drought-tolerant landscape.

Bradford pear (Pyrus calleryana var. Bradford) has the most brilliant burgundy fall foliage of any tree, but its clusters of branches grow out from a single point and their breakage is a constant concern. The foliage of birch (Betula spp.) and willow (Salix babylonica) trees turns a pleasant golden color, but as two of the most water-needy trees, the wisdom of planting them is now questionable, in addition to the fact that willows are short-lived in any case due to early death from foliar fungus diseases.

Probably the two most reliable trees for golden fall color are Modesto ash (Fraxinus velutina var. Modesto), although it can occasionally defoliate due to disease, and ginkgo (Ginkgo biloba), as long as your plant the male ginkgo since the female produces slippery, malodorous fruit.

Island oak Quercus tomentella (Photo by Joshua Siskin)

California Native of the Week: Island oak (Quercus tomentella), indigenous to the Channel Islands and Guadalupe Island off of Baja California, has a more lush demeanor than most other native trees and easily withstands a frost. Sunset Western Garden Book calls it “the handsomest of California’s evergreen oaks.” It exhibits strong and rapid vertical growth, reaching a height of around 50 feet and thrives in full to partial sun with a  minimum of water, although it will be a bit thirstier grown inland than near the coast.

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