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.

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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.