City Nature Challenge Starts Friday

Over four days starting this Friday, which cities worldwide will engage the most people to record the most observations of wildlife and plants, and find the most species? This is the City Nature Challenge, and it’s open to all, including you. Last year, 68 cities participated and tallied 441,888 observations by 17,329 people. This year, more than 160 cities around the globe will join this citizen science effort.
The free iNaturalist app ( is how data is recorded by those participating in the City Nature Challenge. First, install the app, or the even snazzier Seek version ( on your smart phone or tablet. Second, with a fully charged device, go outside from Friday, April 26 through Monday, April 29 and photograph living things with the app. Seek will tell you instantly what you have seen. The standard version can be asked to suggest possibilities. Third, be sure to upload your photos to iNaturalist. Save precious battery power by uploading your images from your home computer. Scientists and researchers will help identify your findings. To reduce their burden, do not submit photos of your pets, common birds or commonly cultivated flowers. No fido, no robins, no tulips. A short instructional video about how to use iNaturalist can be found here:
If you plan to focus on trees, take several photos: one with the entire tree and its surroundings, one of the branching pattern (alternate or opposite), one of the bark, one of the leaves and any flowers or fruit, and be sure to include any evidence of pests or disease. Submit all of the images of the same subject so that scientists have a better chance of correctly identifying what you saw. Your aim is to get “research grade” status for your work. Sometimes a piece of white paper or foil can help illuminate your subject, such as bark or a stationary salamander, so that researchers can see more detail of telltale markings.
For those fascinated by fungi, a good technique is to take a mirror with you and place it under the subject so that in one shot you can capture the base, stem, connection to the cap, gills and top of the mushroom. Detail of the area where the stem connects to the cap is crucial in identifying fungi with photos, so be sure to focus on that.
This type of crowd sourcing allows scientists worldwide, including many at our own Smithsonian Institution, to mine the data for information they need to track species. You might even find a new species! It has happened in our area before with insects, so go chase some bugs with your phone and see what turns up.
Last year, the DC Metro area did well during the City Nature Challenge, according to Alonso Abugattas, writing on the Capital Naturalist blog. He said the area’s 22,809 observations ranked it fifth overall, behind San Francisco—which with Los Angeles started the competition three years ago—(41,737 observations), Dallas/Fort Worth (34,218 observations), San Diego (33,448 observations), and Klang Valley/Greater Kuala Lumpur (25,287 observations). Just behind DC were Houston and New York. Coming in last was Palmer Station Antarctica, whose three participants had 36 observations of 27 species. Globally 124 new species were added to the iNaturalist data base that had not been present before.
     Participation by 876 individuals ranked our area fourth, behind San Francisco (1,532 observers), San Diego County (1,211 observers), Boston (992 observers), and just ahead of Los Angeles (855 observers).
The DC area came in eighth last year with 1,855 verified species observed during 40 planned events, 25 of them in Arlington. This year, more than 124 local events are planned. Check them out and sign up for events sponsored by Arlington County at Those under the auspices of Arlington Regional Master Naturalists are at For area-wide events, go to

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2018 Annual Report

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Vine Finding on a Fine Afternoon

Tree Stewards, trainees and other environmentalists headed out along Holmes Run in Alexandria Sunday to find native and invasive vines after learning how to distinguish them from a slide lecture by noted naturalist Rod Simmons.

First stop outside Beatley Library was an American elm (Ulmus americana) bursting with light-green ripening fruits on the bank of the old Holmes Run channel.

Tree Stewards and other environmentalists admire an American elm laden with light-green seeds. Photo by R.H. Simmons
Tree Stewards and others admire an American elm laden with light-green seeds. Photo by R.H. Simmons
Detail of American elm fruit. Photo by Jo Allen
Detail of American elm fruit, above, pointed out by Rod Simmons, hand raised, below. Photos by Jo Allen
Rod Simmons, hand raised, describes the elm fruit.
Porcelainberry's wiry tendrils dig into tree bark as the vine climbs.
Invasive porcelainberry’s wiry tendrils coil around branches, digging into tree bark as the vine climbs. Nearby, an Eastern rat snake, sunning itself near the sidewalk, found the group disturbing and slithered off.
Several wild grape vines (Vitis spp.) have co-evolved with native trees and grow up with the trees, draping themselves over limbs as they reach for sunlight. Unlike invasive English ivy (Hedera helix), with green leaves on the same tree, grapes and other native vines do not harm tree bark.
Several wild grape vines (Vitis spp.) have co-evolved with native trees and grow up with the trees, draping themselves over limbs as they reach for sunlight. Unlike invasive English ivy (Hedera helix), with green leaves on the same tree, grapes and other native vines do not harm tree bark.
A native grape vine loops over a tree branch on the north bank of Holmes Run.
A native grape vine loops over a tree branch on the north bank of Holmes Run.
On the north bank of Holmes Run, a beaver felled a tree and gnawed off the lower bark.
On the north bank of Holmes Run, a beaver felled a tree and gnawed off the lower bark.
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Learn About Native Vines and Trees

Vines and Trees lecture and walk announcement
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Top Ten Least Wanted Invasive Plants

In Northern Virginia, there are several plants we and trees would be better off without. Some strangle trees, some add enough weight to topple them, and some grow so vigorously that tree saplings don’t stand a chance in natural areas these nasty weeds have invaded.

Here they are, illustrated in slides from Sarah Archer, Arlington County’s invasive plant and natural resources specialist.

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Big Trees Need Your Help

They soak up rain, sway in wind, spread seed to create more trees. But they cannot fight off invasive plants without helping hands from humans, who benefit so much from trees’ shade and shelter.

Woman holds a large root system from a privwet plant.
Tree Stewards trainee Gretchen Crowley holds a privet root unearthed from East Falls Church Park.

Do this to help trees: Volunteer as Tree Stewards trainee Gretchen Crowley has done to rip out the roots of invaders like privet from East Falls Church Park. Tree Stewards and Master Naturalists are ripping invasive plants from 10 a.m. to noon Tuesday, March 26 in East Falls Church Park, 1730 N. Roosevelt Rd., Arlington. Meet at the basketball court to sign in and tool up. We have gloves and sharp objects to lend. We welcome teens, as long as their parent or guardian stays with them for the duration.

The big prize this month could be a delicious batch of garlic mustard pesto. You pull the garlic mustard, then make the pesto. Or just use the leaves in salad for a touch of garlic flavor.

We and Gretchen hope to see you Tuesday!

Jo Allen and Amy Crumpton
Every Last Weed, Every Last Tuesday RiP in East Falls Church Park

This RiP is sanctioned by Arlington County’s Department of Parks and Natural Resources.

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Protecting Sentinel Trees by Removing Ivy

Eileen Grant and Lynn Gas pulling ivy from trees on a hillside at Ivy Hill Cemetery.
Tree Stewards Eileen Grant, left, and Lynn Gas, right, helped trees In January at Ivy Hill Cemetery in Alexandria by removing invasive ivy. Tree Stewards, Master Naturalists, Master Gardeners and other volunteers, led by city Natural Resources Division staff, will conduct a second Invasive Removal Event (IRE) on Saturday, March 16 from 1:30 to 4 p.m. at the cemetery. Photo by Tree Steward Jane Seward

Sign up here to volunteer Saturday afternoon, March 16!

still of video on removing invasive ivy
Click here to watch a short video about the event and the dangers of ivy.

Don’t just stop at trees! Here are 40 reasons to remove ivy from your yard. Thank you, Colin Purrington, for compiling this list. The environmental destruction caused by English ivy (Hedra helix) is a classic example of why native plants, which evolved to support native bees, caterpillars, butterflies, birds and mammals, are always the best choice.

Posted in Alexandria Tree Canopy, Community Service, Continuing Education, Invasive plants, Ivy Hill Cemetery, Mature Trees Are Valuable, Protecting Sentinel Trees, Tree Care, Volunteer | Tagged , , , , ,

Dichotomous Key Update by Emily Ferguson

Click here for the key to winter tree ID with buds and twigs.

Posted in Bark, Education, Training Materials, Tree ID, Volunteer, Winter tree ID | Tagged , ,

Tree Anatomy for Tree Stewards

Trainees, you’ll want to refer to this valuable Tree Anatomy lecture by Jim McGlone  when thinking about pruning trees, or answering the upcoming Module 2 quiz.

Posted in Class Presentations & Materials, Continuing Education, Education, Events, Growing Tree Canopy, New Training Class, Pests, Rainfall, Training Materials, Tree Care, Uncategorized, Volunteer

Books for Tree Lovers

We asked Tree Stewards and our valued partners to share some of their favorite tree books, and here are a few worth putting on your wish list. Others will be added as more members contribute suggestions.


On Sale Now!

Casey Trees Species Guide

If you’ve ever seen a tree and wondered what it was, this waterproof guide with more than 70 species found in the Washington metro area is for you. [Editor’s Note: Tree Stewards trainees received this highly coveted book as part of their course materials. Now, for the first time, it’s available to all for $30, which includes a $20 tax deductible contribution to the fine work of Casey Trees. Click here.] All proceeds go directly towards our Park Inventory program, which gives us a better understanding of the current tree stock of the District. You can’t protect what you don’t know. —Casey Trees

City of Trees: The Complete Field Guide to the Trees of Washington, D.C.

By Melanie Choukas-Bradley

The best guide for this region, as it has every possible tree species you could find in the area. Most other guides either miss ornamental or native trees, but this one has it all. No pictures, but precise local knowledge on where to find every species and excellent descriptions of the trees. Illustrations by Polly Alexander. —Vincent Verweij, Urban Forest Manager, Arlington County

Nature’s Temples: The Complex World of Old-Growth Forests

By Joan Maloof

An amazing exploration of the value of forests and particularly old-growth forests.

Trees of North America and Europe


By Roger Phillips

The best picture book I have for tree ID. This was given to me by Tree Steward Don Walsh, and I highly recommend it.

Up by Roots

By Jim Urban

A more technical guide of how to make a space for healthy trees in an urban environment. —VV

Dirr’s Hardy Trees and Shrubs

By Michael A. Dirr

This may seem old (1997) and expensive ($76 to $143) too, but I still love its fine color photos of a tree or shrub’s most salient features. Dirr’s personal observations about what is worthwhile about each selection and some growth parameters are particularly useful to both new and experienced gardeners looking for that special woody plant for a space to be filled with just the right choice. I bring this book to the tree distributions in Arlington at which I volunteer. Shirlington Library has a copy to lend. —Lynn Barton, TSAA
[Editor’s note: This volume has been updated and named Dirr’s Encyclopedia of Trees and Shrubs, with 3,700 species, 3,500 photos, and lower price, $41.40 hardcover. At 952 large-format pages, it makes a dandy doorstop when not otherwise occupied.]

Whitetail Savvy: New Research and Observations about the Deer, America’s Most Popular Big-Game Animal

By Leonard Lee Rue III

Some time back a [Capital Naturalist] group member suggested reading Whitetail Savvy by Leonard Lee Rue III. I really loved the book because it answered all my questions about my deer neighbors and some I hadn’t thought to ask. It is widely available, from used book sellers, from Amazon, as an ebook. It runs in the $20 +/- range and might make a good holiday present. This author has raised deer herds and studied deer in the wild for decades. If, like myself, you are not a hunter, you just need to ignore or get over those parts. It’s clear he respects the animals. Just FYI. —Robin Young via Capital Naturalist on Facebook

The Wild Trees: A Story of Passion and Daring

Cover: The Wild Trees
Cover: The Wild Trees

By Richard Preston 
Join this nonfiction quest to find and climb the tallest organism on Earth, a California redwood, Sequoia sempervirens. This is the true story of Steve Sillet, Marie Antoine and the daring amateur naturalists and botanists who discovered a new world, with species previously unknown to science, living in soil in the treetops more than 300 feet above the forest floor. This tale has everything: adventure, courage, failure, love, and treetop sex. If The Wild Trees doesn’t make you want to climb a tree, nothing will. —Jo Allen
Amazon review. Kirkus review: Enthralling.

The Hidden Life of Trees: What They Feel, How They Communicate ―Discoveries from A Secret World

hidden life trees cover

By Peter Wohlleben
German forester Wohlleben demonstrates how trees have survived for millennia against daunting odds: They communicate through chemical means, giving sugars to their offspring and signaling pest invasions that allow their neighbors to arm their leaves. The criticism that Wohlleben goes too far down the trail of anthropomorphism is indeed valid. Nevertheless, it will give you a new perspective on forests. —JA
Amazon review. New York Times mini review.

Seeing Trees: Discover the Extraordinary Secrets of Everyday Trees

Cover: Seeing Trees

By Nancy Ross Hugo; Photography by Robert Llewellyn
Look no further than this gorgeous large-format book for a crash course in tree identification. Anyone who digests the descriptions of 10 “everyday trees” and the useful advice about where to look, what to look for, and what it tells will surely ace Tree Stewards! The photographs are fantastically dreamy and ethereal while being perfect illustrations of the text. —JA

Bark: A Field Guide to Trees of the Northeast

By Michael Wojtech

Lavishly illustrated with color photos of the bark of dozens of trees found in the Northeastern U.S., this book is helpful for trying to identify trees in winter when their telling leaves are missing. Wojtech has affixed a quarter, to show scale, on many of the trunks and shows how bark patterns change, sometimes radically, as trees mature and age. Illustrations of bark patterns are useful in the key, and each tree’s branching pattern and leaf outline also help with identification. A gem. — JA

The Sibley Guide to Trees

By David Allen Sibley

Here’s the guide to carry into the woods on your next tree ID trek. It clearly, with bark, branch, bud, flower, fruit and leaf illustrations nails more than 600 tree species, both native and introduced, and includes many maps to show species distribution. Some habit information is included for some species, but not all. So if you want to grow one of these trees, you should consult an online .edu site for sun, shade, water, soil, and other preferences before buying or planting. —JA


The Overstory

overstory cover

By Richard Powers
Here’s an epic novel, set in all corners and the middle of America, uniting disparate souls with a common quest that slowly overtakes them: to better understand and protect trees. Powers brings together an electrocuted co-ed, a wood carver with the last surviving American chestnut tree on his farm, a high-powered businesswoman, a homeless man and others as they edge ever closer to the old-growth redwoods, doing what they can to keep the chainsaws and loggers at bay. It’s a fast and fascinating read, and you’ll learn more about trees than you ever dreamed. —JA

New York Times Bestseller
Shortlisted for the 2018 Man Booker Prize
A New York Times Notable, Washington Post, Time, Oprah Magazine, Newsweek, Chicago Tribune, and Kirkus Reviews Best Book of 2018

Amazon review.

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