Posts Tagged ‘street trees’

Guest Post: Our Exotic Urban Forest

This is a guest post by Nancy Nordman from Our City Forest, San Jose’s urban forestry group. Our City Forest is a non-profit organization that provides free trees and tree advice to San Jose residents and promotes greenery in our urban environment. They’ve planted some 65,000 trees in San Jose! Here, Nancy takes us on a tree walk of the urban forest around San Jose’s Rosicrucian Egyptian Museum. Why not poke around and see what’s growing in yours?

When I first started as an AmeriCorps member at Our City Forest, I probably couldn’t name even ten different tree species, let alone classify the species I was standing under.  I knew plenty about how trees used photosynthesis to make food and I definitely had an appreciation for the benefits trees provide to us and the environment.   But ask me to tell the difference between an Ash and an Elm?  At that point, your guess was as good as mine.

Once I found out I would be leading tree tours around the city, I began to poke around looking for any information that could help me – field guides, the internet, and my enthusiastic co-workers.   I found there to be incredible diversity just among the 65,000 trees planted by Our City Forest. I  began to see opportunities everywhere I looked for more greenery to be added to this city to make it healthier, more efficient, and more beautiful.

At Our City Forest, we are often asked why we allow any planting of non-native trees.  While we are a strong advocate of planting native trees, there are numerous situations where planting non-natives actually makes more sense.  As the city of San Jose has grown, urbanization has drastically altered the native environment, so some natives can no longer thrive in the urban setting.  Oftentimes we plant drought tolerant non-native trees from similar Mediterranean climates that can handle harsh urban challenges such as smog.  Species diversity is also incredibly important to maintaining the health of an urban forest so that if a disease comes through, the tree population can make a comeback.

The wonderful thing about all this diversity is that you don’t need to go somewhere special to see a bunch of different trees!  I encourage you to take a walk along your street and just try to notice the urban forest around you.  To get you started, here are some great trees to check out at the Rosicrucian Egyptian Museum in San Jose.  (There are around 50 different tree species within the grounds of the Rosicrucian Museum alone!)

Canary Island Palm. Photo credit: Our City Forest

Canary Island Palm (Phoenix canariensis)

Where better to start than a “tree” that is not really a tree?  Palms are technically classified as grasses.  Unlike true trees, palms do not undergo secondary growth and therefore do not produce true wood, but rather a fibrous trunk structure.  There are also differences in their growth and structure as well as their root system.

In contrast to the equally common Mexican Fan Palm, Canary Island Palms are shorter and stockier and have pinnate feathery leaves instead of the fan palmate structure of the Mexican Fan Palm.  If you still aren’t sure which palm it is, look underneath the feathery stalks hanging down and you can usually see what looks like a large pineapple.   The Canary Island Palm does in fact come from the Canary Islands and is highly ornamental, sporting large, orange, edible dates.

Jacarandas in bloom. Photo credit: Frank Reyes

Jacaranda (Jacaranda mimosifolia)

If you are looking to see some color in our urban forest, keep your eyes peeled for the gorgeous Jacaranda trees!  Though found all over San Jose, these trees originate from the tropical environment of Brazil and Argentina and have since been introduced all over the world.  Their popularity is thanks to the large showy violet flowers that appear in late spring or early summer.  Also interesting to note is the large brown clamshell seedpods and the fern-like compound leaves.  These trees are located throughout the museum grounds, but are mainly located near the obelisk.

Irish Yew. Photo credit: Our City Forest

Irish Yew (Taxus baccata)

On the side of the museum directly across from the Starbucks, you will see two short stocky bush-like trees.  But don’t be fooled, they may look tiny but these trees are some of the most formidable trees on the whole grounds!  Bearing toxic wood and leaves, these trees are also extremely long-lived, up to 4000 years!  It is said that bow makers and other wood craftsmen would get sick from working with this wood.  Originating in Europe, this tree was often planted in cemeteries as a symbol of transcendence after death.  They can be identified by their flat dark green leaves and red seeds, which are very much enjoyed by bird species that don’t find them toxic.

White mulberry. Photo credit: Our City Forest

White Mulberry (Morus alba)

If you cared for silkworms in elementary school, you may know that they will only eat mulberry leaves.  The White Mulberry is appreciated here in San Jose for its fast growth and ability to handle pruning.  Less known but certainly more impressive is its ability to shoot out pollen at 350 miles per hour — one of the fastest movements in the plant kingdom!  There is a particularly great White Mulberry on the museum grounds next to the Akhenaten Shrine and near the Peace Garden.

Olive tree. Photo Credit: Our City Forest

Olive (Olea europea)

Possibly my favorite tree yet is the Olive tree, mainly for its incredibly beautiful silver-gray leaves and whorled trunk.  You likely know this tree for its production of olives, or perhaps from its history of use for crowns in ancient Olympic games. The Olive tree does very well in San Jose’s climate because it originally comes from the Mediterranean Basin, making it quite drought tolerant.  Worldwide, the olive tree stands for peace and wisdom and the museum has dedicated a large section of the grounds to these magnificent trees.

Dawn Redwood. Photo credit: Our City Forest.

Dawn Redwood (Metasequoia glyptostroboides)

Tucked in a corner by the library and rose garden of the museum, you will find a gem of a specimen—a huge Dawn Redwood!  These fantastic trees were actually widely thought to be extinct, but as they were attempting to classify fossil records of the leaves, a matching specimen was found in an area of central China.  Similar to the ginkgo, this tree is considered a “living fossil.”  Don’t be surprised if you find this tree looking dead in the autumn and winter.  The Dawn Redwood is the only living deciduous redwood species and so it will turn a beautiful bronze color and then drop its feathery leaves, taking on a skeletal appearance.

Bunya Pine (Araucaria bidwilli)

To the left of the main entrance to the museum are a couple of Bunya Pines, which are an interesting evergreen species from Southeastern Queensland.  Take a close look at the branches which have tufts of leaves at the ends and few by the trunk — but do watch for large falling seed cones!  The edible cones get as heavy as 10-15lbs, so during fruiting season this tree can be quite dangerous!  From far off, it is very pretty with its branches forming a rounded dome structure toward the top.


I hope you enjoyed this brief tour of the unique non-native trees you can discover in San Jose!  As I continue to learn more about trees, I find my appreciation of their beauty and function is constantly growing.  Trees are already working hard filtering pollutants out of the air, cleaning our water, and providing home for critical wildlife species.  I hope you will join Our City Forest in advocating for a vast and healthy urban forest!  If you wish to learn more about trees and urban forestry, check out the Our City Forest website, like us on Facebook, come out and volunteer with us, or consider getting a tree from our nursery!  We also have free educational tree tours and classroom presentations.  Our City Forest is a nonprofit that has been providing free trees for residents, schools, and parks across San Jose since 1994.  For more information on our planting, tree care, and educational programs, visit our website or call (408) 998-7337.

Jennifer: Do you know what’s growing in your urban forest? On my street are maples, ashes, sweetgums, olives, birches, redwoods, redbuds, gingkos, and Chinese pistachios, just to name a few. Going on a tree walk with a knowledgeable local is a great way to learn about the forest you live in. Thanks, Nancy!

Why Trees Matter

If you turn your head to the side and squint, ash tree bark kind of looks like ocean waves at sunset.

On Friday, the city cut down the healthy 50 year old ash tree outside my bedroom window. The reasons cited: streetlight and minor pavement damage. I’m no Julia Butterfly Hill, but when the notice first went up, I complained to the proper authorities, who assured me that the site would be re-evaluated. That was the last I heard when the men with the saws came. For six hours, the  roar of the chainsaw ground through my bones. All day, I felt cold, queasy, and thoroughly ashamed at my species. What  kind of society values a streetlight and concrete over a beautiful, mature, living tree?

Part of it was the timing. I’m currently reading The Man Who Planted Trees by Jim Robbins, which is about David Milarch‘s quest to preserve and clone the trees most likely to survive in an inhospitable future.  I had just read this stunning figure: as of 2010, about 8 million acres of lodgepole and ponderosa pine in the US and 43 million acres in Canada have been killed by bark beetles. I can’t even imagine what 51 million acres looks like. Milder temperatures caused by climate change have extended the destructive beetles’ season from two weeks to six months, broadened their range, and increased their victims from mature trees only to saplings. There’s even some evidence that pine beetles are starting to attack other tree species. And warmer weather often means dryer conditions, which stress already vulnerable trees. The bottom line? 6.3 measly degrees is going to make a huge difference for trees. How much, we don’t really know — there’s an overwhelming lack of information when it comes to tree research.

Even if we stopped logging right now (78% of our ancient forests around the world have already been cut down), our trees would still be in trouble from climate change. As the author says, “The only thing harder on trees than beetles, it seems, is people.” Ouch.

If you consider yourself a tree person or even someone moderately invested in the future of humanity and this planet, you should be deeply concerned about a future with fewer or no trees. Trees matter. I’ve come up with an idiosyncratic and incomplete list of why. (Many are taken from Robbins’s book, which I recommend.)

  1. Trees have a net cooling effect in city as well as forest settings. According to the USDA, “the net cooling effect of a young, healthy tree is equivalent to ten room-sized air conditioners operating 20 hours a day.” Unfortunately, warmer conditions under climate change kill trees, and losing trees leads to warmer conditions, and there you have it — a positive feedback loop and a perfect recipe for climate destabilization.
  2. Massive flooding in Thailand, China, and Pakistan has been partially linked to deforestation.  Trees ameliorate flooding, absorbing and slowing waterflow, protecting river banks against erosion and run-off, and replenishing water tables. Clear cutting these natural barriers aggravates flooding.
  3. Many trees are considered keystone or umbrella species that an ecosystem would collapse without. Protecting, say my beautiful coast redwoods, protects a vast array of animals and plants that redwoods support.
  4. Trees absorb carbon dioxide and produce oxygen. Duh. According to the USDA and the Arbor Day Foundation, “an acre of forest absorbs 6 tons of carbon dioxide and puts out four tons of oxygen. This is enough to meet the annual needs of 18 people.” I wonder what our current forest / human ratio is?
  5. Trees can lower energy bills. Plant them strategically to produce shade and reduce wind. According to Dr. McPherson of the Center for Urban Research, planting one tree on the west side of your house will yield about 12% energy savings in 15 years. (Yes, it takes a while. But as the saying goes, the best time to plant a tree was 20 years ago. The second best time is now.)
  6. Trees scrub our world clean of toxic substances. They can clean up toxic waste better and cheaper than conventional cleanup. It’s called phytoremediation. The roots absorb and break down substances like ammonium, nitrogen, pesticides, and nitrogen run-off from farms that cause dead zones. They can even deal with things conventional methods can’t extract, like pharmaceuticals and endocrine disruptors. One willow can process 15 gallons of waste a day.
  7. Seeing trees makes humans less crazy. Going for a walk in the woods helps kids with ADD concentrate and increases anti-cancer proteins in cells. Proximity to green space reduces the rate of anxiety disorders. Even having a home view of trees cuts down on aggressive conflicts with family members. How do they do it? One theory is that tree gives off a chemical cocktail as an aerosol.
  8. Civilizations that cut down all their trees collapse. This is Jared Diamond’s theory, not mine, but he provides so much proof in Collapse that it’s hard to disagree with his central thesis that misusing our natural resources predictably comes around to bite us in the ass. Money is not edible. To paraphrase Diamond, “being rich just means being the last to starve.”

Trees plainly deserve more attention in the green conversation than they’ve been getting — more research money and energy, too. When I read my Twitter feed and come across yet more articles on miniscule impacts to human health (chemical x is linked to cancer / asthma / infertility / whatever human ailment), I just want to shout, “Hey! Other species besides humans matter!” And then I grumble in my head about why we’re wasting so much energy and money investigating infertility when, at 7 billion people + and rising, infertility is clearly not a major problem humans are facing. But I digress.

While writing this entry, I’ve decided that my next move is to harangue the city arborist again.  If the city budget won’t stretch to replace my cherished street tree, I’ll pay for it myself. It’ll be worth it, emotionally as well as ecologically.

When’s the last time you thought about trees? Did I miss anything major on my list of why we should give a damn about them? (Maybe just the fact that they’re beautiful and fascinating and we don’t really know that much about them?)

Photo credit: Redwood Canopy by Tolomea

Looking at Trees, Part 1: Winter

Time for a confession: I don’t actually hug trees. I’m not a big hugger to start with, and trees are scratchy and unyielding. Many have ants trailing up the grooves, baby snails hatching in knots, sap dripping down in slow motion. I may not be a literal tree hugger, but I am a tree lover and an enthusiastic tree watcher.

My tree book collection has exploded in the past year with natural histories, field guides, and photography books. In the space of a year, I have started to look — really look — at trees for the first time. I was originally going to write this post in the fall, when trees still had leaves. But winter is actually a very good time to start looking at trees. Leaves can be so distracting. Without them, you can see the bones underneath and appreciate the architecture.

Precise tree identification is probably best left to the experts, but it’s actually not very hard to get started with the basics. I’d like to share a little of what I know in hopes that the boring old tree outside your window will suddenly become a lot more interesting. My earliest tree lessons came from my mother, who gave me the names to eucalyptus, liquidambar, and mulberry trees early in my childhood. I’m grateful. (Incidentally, this post is only about broad leafed trees. I’m just not that into conifers yet, other than the wonderful coastal redwoods I grew up with. Sorry.)

Looking at Branches: Opposite vs. Alternate

If you can categorize a tree as having opposite branches, you can rule out a whole lot of other possibilities. Only a few tree families have opposite branches, and there’s a handy little mnemonic to help you remember which: Damp Horse (dogwood, ash, maple, paulownia, and horse chestnut). Winter is a good time to check out whether your neighborhood trees have opposite or alternate branches. Be careful, though. While black ashes form clear, dark crosses across the sky, you’ll have to look closer with most other trees. Also, alternate trees will have the odd opposite pair, and vice  versa. If you see many pairs of opposite branches, however, you’re probably on to something.

See the way the branches grow out opposite each other to form Vs or crosses? This is an ash tree.

Looking at Fruit/Seeds

Botanists have lots of different names for different types of fruit (drupes, pomes, arils…). I don’t know all of them yet, and you really don’t need to in order to pick out several of the major tree families.

Acorns = Oak (Quercus)

Only oaks bear acorns, so if you see green acorns on a tree or brown acorns beneath one, you’re looking at an oak. Oaks are a crazily diverse family of trees. This photo shows an oak with smooth, deeply lobed leaves, but there are also oaks with sharp lobes (black oak), small spiny leaves (coast live oak), and even smooth, elongated oval leaves (holly oak). Most oaks lose their leaves in the fall, but live oaks stay green year round.

As a very rough generalization, most mature oaks are stout trees with irregular (non-symmetrical) crowns and gnarled branches and trunks.

Paired Samaras = Maple (Acer)

I probably don’t have to tell you what a maple leaf looks like, but not every tree that has maple-like leaves is actually a maple (see plane trees, next), and if that wasn’t enough, there are also maples with leaves that look like ash leaves (box elder). However, all true maples have paired sets of winged seeds, which are called samaras. They spin like helicopters when you drop them, and I’ve always thought they were an instance of awesome design by nature.

Maples include sugar, silver, and Japanese varieties. Many maples turn beautiful colors in the fall, especially on the east coast. Branches are opposite, and as far as I know, all maples are deciduous.

Soft Seed Balls = Plane Trees / Sycamores (Platanus)

 If you see a bare winter tree with camouflage like bark (big gray, white, tan, and/or orange splotches) and 1″ seed balls hanging down, especially near the top of the tree, you’re looking at some sort of plane tree (sycamores in American English). The seedballs are a little spongy and surprisingly light for their size. If you pull one open, you’ll find that it’s filled with white fluff, and the brown outside is actually formed of lots of tiny seeds packed together. They’re kind of like inside-out dandelion puffs.

Plane trees have big maple-like leaves, but good luck trying to tap one for syrup. At least in my area, they are one of the most common street trees.

Wicked Spiky Seed Balls = Sweetgum / Liquidambar (Styrax)

There are probably other trees that produce round, brown seed balls. But the sweetgum is so common and distinctive that I thought I’d point it out to you. The sweetgum has star-shaped, vaguely maple-like leaves that turn brilliant colors even in mild California autumns, and after they’re all gone, spiky seedballs hang down from the bare branches like ornaments. Unlike the plane tree’s seed balls, these are spiked all over and very hard. The seeds are dispersed through holes in the ball, leaving the spiky structure intact. These things decompose very slowly — amid the brown ones of this year, you can often see grayer, smaller seed balls of previous years.

Whew! I could go on for a while, but I don’t want to be a bore. I noticed today that some of our street trees (Bradford pears) are already putting out new buds. California trees live in a state of perpetual confusion about when they’re supposed to do what. In the spring proper, I’ll bombard you with information about flowers and leaves.

Have you ever taken a close look at your hardworking and underappreciated street trees? What kind of trees are around you?

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