Pin Oak

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Pin oak is not drought tolerant.

There are several oaks, especially natives, that do not need much more water than they get from rain. Pin oak, Quercus palustris, is not one of them. It is naturally endemic to areas that are damp or swampy for part of the year. It is more tolerant than others are to lawn irrigation, but is also more sensitive to drought.

Compared to other oaks, pin oak grows fast while young. It can get two stories tall in about ten years. Then, it takes more than twice as long to double in size. Old trees do not get much more than fifty feet tall, with trunks nearly three feet wide.

The deciduous foliage turns as brown as a grocery bag in autumn, and may linger late into winter, or until it gets replaced by new foliage in spring. The distinctively deeply lobed leaves are about two to five inches long, and about two thirds as wide. Each leaf has five or seven lobes. Each lobe has five to seven teeth.

Streets Are Cooler With Shade

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Parked cars stay cooler in shade.

There really is no such thing as a perfect tree. Some are not quite as messy as others. Some have better structural integrity than others. Some have gentle roots; and some stay proportionate to tight spots. However, without exception, all trees grow, drop leaves, and disperse roots.

This is an important consideration when selecting any tree, and especially when selecting a street tree for the narrow space between the curb and the sidewalk (which is commonly known as a park strip). Even where there is no sidewalk, or where the sidewalk is at the curb, most of the obstacles are the same.

Street trees should have reasonably complaisant roots that should not be likely to damage curbs, sidewalks or roadways, at least for several years. They should naturally develop reasonably high branches. They will need to be pruned higher than trucks that may park at the curb. Street trees must also tolerate harsh exposure.

Wider park strips can of course accommodate larger trees. Those that are only two feet wide or narrower are probably not wide enough for any tree larger than photinia, purple-leaf plum or English hawthorn, which are difficult to prune for clearance over roadways and sidewalks.

Messy leaves, flowers or fruit that might not be a problem within the garden might be more of a problem at the curb. It is not so easy to rake such debris if cars park over it. Trees that are commonly infested with scale or aphid are likely to drop sticky honeydew (scale and aphid poop) onto parked cars.

Unfortunately, those who get street trees do not always get to select them. Many municipalities assign specific trees to specific streets. Some streets have a few trees to choose from. Others have only one option. Home Owners’ Associations (HOAs) decide if and where new trees get planted.

Crape myrtle is probably the most common choice for a new street tree because the roots do not get big enough to damage pavement. However, the canopies are not very big either. They stay too low to be pruned above trucks. Crape myrtle is susceptible to scale infestation that can get bad enough to make sidewalks sticky.

For many years, London plane (sycamore) had been another popular street tree. Unfortunately, the voracious roots can damage pavement within only a few years. The messy foliage discolors and starts to fall before autumn.

Evergreen Trees Have Their Place

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Evergreens are sometimes the best choice.

Deciduous trees that were bare all winter are now foliating and making shade. They sure will be appreciated when the weather gets warmer through summer. They will defoliate next autumn, in time to let warming sunlight through while winter is cool. Their lifestyles are naturally compatible with those of the people who live with them. They really have the system down.

Evergreen trees are good at what they do as well. They obscure unwanted views and provide privacy all year. If given adequate space and located far enough away from the home and neighboring homes, their shade should not be a problem. Like any other feature in the landscape, properly selected and strategically placed evergreens are quite functional.

There are certainly more to evergreen trees than the coniferous (cone-bearing) evergreens like pine, spruce, cypress, cedar and juniper. Any tree that retains foliage throughout the year is evergreen, including camphor, Southern magnolia, carob, California pepper, coast live oak, fern pine, all palms and all eucalypti, just to name a few. There are really too many to list.

Larger modern homes on smaller parcels are a bit more challenging to evergreen trees than more traditional homes that have more space around them. Average fences do not maintain privacy for upstairs windows that are too close to neighboring homes. However, there is less space and sunlight for trees, and additional shade can be a bother for lower windows.

It seems that smaller trees are often the best fit for bigger homes. Sometimes, a large evergreen shrub, like one of the various pittosporums, can do the job of an evergreen tree, but fits better where space is limited. As silly and passe as they seem to be, Italian cypress are narrow enough to fit into tight spots, at least until they get too big.

Contrary to popular belief, most evergreen trees are messier than most deciduous trees. They drop only minor volumes of foliage, but they do so throughout the year. Deciduous plants drop most or all of their foliage within a limited time about autumn. Only those that drop flowers, fruit or both in spring and summer are messier than evergreens.

Pecan

41210One might surmise that a tree that is resilient enough to be the state tree of Texas is not too discriminating. If it can take the heat and humidity of the Lone Star State, it can make it anywhere! However, pecan, Carya illinoinensis, actually prefers heat and humidity, and is bored with the mild local climate. The nuts and the mess that comes with them are actually less abundant than they would be in the Gulf Coast States. The deciduous foliage is not quite so colorful in autumn.

A mature pecan tree may stay a low as fifty feet, or get twice as tall. The height is usually nearly double the width. Generous watering can cause roots to buttress and displace nearby pavement. Most local pecan trees that are intentionally planted are garden varieties that were bred for bigger pecan nuts. Seed grown trees tend to produce nuts that are nearly comparable to the nuts they were grown from. The pinnately compound leaves have nine or more leaflets that are about two or three inches long.

Cottonwood

90724Several native species and varieties of poplar are known collectively as cottonwood. Not many are actually planted. They just have a sneaky way of appearing in well watered parts of the garden that are as damp as the riparian areas that they naturally inhabit. Only Fremont cottonwood, Populus fremontii, gets planted, rarely, and only in big spaces that can accommodate its grand scale.

Although too big and too thirsty for most refined landscapes, cottonwoods work well for shade or erosion control in big parks. However, they need to be in a lawn or irrigated landscape if they are not close enough to riparian areas to disperse their roots into soil that is somewhat moist through most of the year. Even in riparian situations, young trees need irrigation until their roots disperse.

Cottonwoods grow fast and big, with aggressive and potentially destructive roots. They should not be planted too close to pavement or septic systems. Vigorous trees might sometimes need to be pruned to reduce excessive weight. Big trees might grow to nearly a hundred feet tall, with wide canopies. Bark is handsomely furrowed with age. The deciduous foliage turns yellow in autumn.

Mighty Oaks From Little Acorns

90522thumbOak, which might seem to be obvious to many of us, was identified by the Arbor Day Foundation as the People’s Choice for American’s National Tree. We certainly like our redwoods and exotic palms in California. Quaking aspen and blue spruce are probably favorites in Colorado. Sugar maple must be the most popular in Vermont. Yet, everyone appreciates the mighty American oaks.

Connecticut, Georgia, Illinois, Iowa, Maryland, New Jersey and the District of Columbia each have an oak as the official state tree. ‘Oak’ is one of the more traditional names for streets and roads throughout America. Just in California, at least eight towns are named after oaks, both in English and Spanish. Oaks put the ‘oak’ in Oaklahoma! (Oakay, maybe that last one is an exaggeration.)

So, now that we know that oak is what most Americans want to be the National Tree, does anyone know what species the oak should be? Well, that will take a bit more work. There are so many in America. There are too many to select from just in California! They are each so unique too. Some grow into grand trees. Others are shrubby scrub oaks. They might be deciduous or evergreen.

It is important to be aware that, just because oaks are the most popular trees in America, they are not necessarily appropriate for home gardens. Some, particularly in California, are best in the wild outside of landscaped areas. Some get too big. Some are too messy with acorns and leaves that fall slowly for a long time, either evergreen or deciduous. Some are susceptible to disease.

It is also important to be aware that big mature oaks, as rugged as the seem to be, are remarkably sensitive to modifications to their environment. Wild oaks that matured in areas that were not landscaped can succumb to rot in only a few years if the ground below them gets landscaped and regularly watered. Oaks planted into new landscapes adapt to the watering they get while young.

For landscapes that can accommodate them, oaks are grand and elegant shade trees that last a lifetime. There are many good reasons for their popularity.

 

Apologies for posting tomorrow’s article today. Today’s article will be posted tomorrow.

Birthday Trees

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The big wide medians of San Vicente Boulevard in western Los Angeles had been lacking trees since the Red Car Streetcar rails were removed decades earlier. My colleague, Brent Green, had been wanting to add trees to the medians since he was a little kid, and then became intent on doing so after he became a renowned landscape designer in the region.

At about the same time, I was a nurseryman. In my work, it was not uncommon to dispose of a few items that were unsaleable. Sometimes there were entire crops of unsaleable plants; and in 1997, I needed to dispose of a group of coastal redwoods that had very minor kinks in their trunks.

That gave Brent an idea.

He wanted me to bring some of the trees to Los Angeles to plant them in the medians of San Vicente Boulevard just south of the Miracle Mile District. We were sort of skeptical about their ability to adapt to the climate; but were willing to give it a try, and possibly give the trees a second chance. We planned to install thirty coastal redwoods for Brent’s thirtieth birthday on January 18, 1998.

Well, the trees were not happy there, and did not last long. However, they were the first of what became an annual tradition of planting trees on Brent’s birthday, January 18. The number of trees is determined by Brent’s age for the respective year. For example, we planted thirty coastal redwood trees on his thirtieth birthday, and then planted thirty-one manna gum trees, Eucalyptus viminalis, on his thirty-first birthday, and so on.

After a few more years, there was not much space on San Vicente Boulevard, so Brent started planting street trees in the parkstrips of streets that could use more trees. The original trees in San Vicente Boulevard needed to be removed for the installation of the Metro Rail, but they were nice while they lasted.

This short video is about what the tradition has become now that Brent will be planting fifty birthday trees.

 

European White Birch

60120+It may not be the biggest or best deciduous shade tree, but European white birch, Betula pendula, is famous for tall and elegant white trunks with wispy pendulous stems. It is a very informal tree that typically leans in one way or another, but is somehow right at home in refined landscapes. It is rarely alone, since it is usually planted with two or more friends, and sometimes in groves.

Not many of the biggest European white birch trees are more than fifty feet tall locally. (They can get bigger in cooler climates.) The slender trunks do not get much more than a foot and a half wide. As trees mature, the smooth white bark develops rough black furrows. The small triangular leaves turn soft yellow in autumn. The somewhat sparse foliage makes only moderate shade.

‘Laciniata’ has lacy lobed leaves, and stands straighter and narrower. ‘Youngii’ is so pendulous that it can barely stand up without staking.

Bigleaf Maple

81024It is native from the extreme southern tip of Alaska to the extreme southwestern corner of California, but not many of us will see bigleaf maple, Acer macrophyllum, in our neighborhoods. It is planted only rarely, particularly where winters are mild. Relative to other maples, its roots can be more aggressive, and its shade can be darker, so is likely to interfere with lawn and other plants.

Mature trees in exposed situations can get more than fifty feet tall and quite broad. Old wild trees that compete with other trees in a forest can get three times as tall! The big palmate leaves from which the name is derived are about half a foot to a foot wide, and can get a two feet wide on the most vigorous or shaded growth. They turn a nice golden yellow in autumn, even in mild climates.

Bigleaf maple is like the sugar maple of the West. The sap can be processed into maple syrup and sugar. The wood is made into furniture and musical instruments. The very ornamental wood known as bird’s eye maple is derived from burl growth of various maple specie, particularly bigleaf maple. Bigleaf maple is uncommon in landscapes only because it is so aggressive and big.

How Shade Is Made

70816thumbMany of our trees live at our homes longer than we do. Some of our trees were there before we got there. Some of the trees we plant will be there for whomever comes along after we are gone. Trees very often evolve into something very different from what they were intended to be. Nonetheless, since they are the most significant features of our gardens, trees must be selected carefully.

The recommendation that shade trees near the home should be deciduous is cliché but accurate. It makes sense that the trees that provide cooling shade in summer will also allow warmth and light through while bare in the winter. Evergreen trees are better for obscuring undesirable views around the perimeter of the garden, where they will not shade the home too much through winter.

The problem is that many modern gardens are too small for such diversity. Modern homes are so close to each other that evergreen trees are more important for obscuring views. Consequently, evergreen trees that provide privacy between homes and gardens might also function as shade trees. Limited space also means that trees affect neighboring homes and gardens significantly.

This is why so many of the small trees (that are known almost disdainfully by some arborists as ‘microtrees’) are so popular. Japanese maple, flowering cherry and smoke tree that were once popular for atriums and small enclosed gardens are now popular shade trees. Realistically though, some modern backyards are not much bigger than what was once considered to be an atrium.

Small evergreen trees or large shrubbery, like Australian willow, mayten, photinia and the larger pittosporums, work nicely by providing both privacy and shade for small areas. Contrary to popular belief though, evergreens are generally messier than deciduous trees. They drop small amounts of foliage throughout the year instead of dropping most or all of their foliage within a limited season. Flowers or fruit add another dimension of mess, even for deciduous trees like crape myrtle, flowering crabapple and saucer magnolia.