Insider is a mix of sources and references used in compiling Stikky Trees, trivia, things we left out, and known errors

It also provides some insight to anyone interested in the thinking behind the Stikky method.

If you have a specific question you would like to see addressed here, email : insider1 (at)

The Top 10 Trees in the U.S. by State
Find out which trees are likely to be growing in your backyard. Or, the next time you go on vacation, you can get a sneak preview of leaves to be looking out for along your way.

3: Trees are mini oxygen factories. Trees consume carbon dioxide and emit oxygen; humans do the reverse. But the situation isn't quite that straightforward since, when trees die, they also consume oxygen as they decompose. Actually, it's not that straightforward either, since the oxygen used in decomposition is actually used by organisms feeding on the trees. So you can see that any claim along the lines of "trees/animals use/produce oxygen/carbon dioxide" is not the whole story.

6: Oldest living thing. At least, oldest that we know of. The verified oldest living tree is a 4,700 year-old bristlecone pine residing in the White Mountains of California. See

7: (Logging train photo.) A logging train winding down from the fir forests of the Cascade Mountains in the US Pacific Northwest.

54: Aspen. This was by far the most difficult photograph in the book to get. It involved a lengthy train ride to Pelham, north of New York City, followed by a cab ride with a driver who had no idea where we were going. We finally found the promised stand (ie, group) of aspen trees in Pelham Bay Park, next to the parking lot.

62: If they are plural, it's a pine. The first draft of Stikky Trees included the tamarack, a needle tree with bundles of lots of needles. But tamaracks are not very common in the US and space constraints meant it had to be dropped. The tamarack also presented us with another problem: nature being adept at providing an exception to every rule we can invent, tamaracks are the only trees with needles that are, in fact, deciduous not evergreen. This is the sort of thing that is fun to know now, but not much fun when you're trying to learn the basics.

84: The 10 most common trees in the US. The top 10 data was compiled from new research based on the USDA Forest Service database. (Miles, Patrick D. Aug-10-2004. Forest inventory mapmaker web-application version 1.7. St. Paul, MN: US Department of Agriculture, Forest Service, North Central Research Station. Available only on the internet: We grouped trees into genera (the plural of 'genus') rather than species to make it easier to learn for beginners. Once you know the genus, it's relatively easy to add species (white oak, red oak); but if you don't know genera, species just look like an impossibly long list.

87: #9. Actually the ninth most common tree is Juniperus which includes junipers but also the misnamed red cedar. Scientists typically give precedence to the earliest name for a species, not the most correct, so red cedar stuck. (Other cedars are in a different genus--Thuja.) In short, cedars and junipers are a mess and we didn't want to confuse readers at this early stage.

94: Douglas-firs only grow in the western US. Actually, the Forest Service database shows a few Douglas-firs in Pennsylvania.

132: It's about 50 years old. This is based on the a rule thumb quoted in Peter Thomas's Trees: Their Natural History: temperate (ie, not tropical) trees add one inch to their circumference each year when growing in the open, half an inch in woodland. Very young and very old trees may diverge from this rule and, anyway, every species is different. Now the average person's arm span is roughly equal to their height, and the average height in the US is 5 feet 8 inches, or 68 inches. So a one arm-span tree would be around 70 if growing in the open and 35 in woodland. We average this to 50 though, admittedly, that means our rule is wrong almost all the time, but a good order-of-magnitude estimate most of the time.

135: The woman in the photograph is the Stikky designer.

139: The woman in the photograph is not the Stikky designer.

144: Race upwards to the light. This insight is from Tom Wessels' Reading the Forested Landscape.

149: One leaf, several leaflets. You can tell a leaflet from a leaf because leaves have a bud where they join the branch but there are no buds next to leaflets (instead there is a bud where the whole twig joins the branch).

156: All clones of a single aspen. Clones--often thought of as bizarre monstrocities--are, of course, just identical twins.

166: The bark of most trees is ridged. We didn't have space to explain why different trees have different bark. Birches, for instance, shed their bark like snakes shed their skin. Oaks, on the other hand, grow new bark underneath and let the old layers burst off, leaving ridges. See T C Whitmore (1962) 'Why do trees have different sorts of bark?' New Scientist, 312 (8 November), 330-1.

192: Many of the trees you come across. According to the Forest Service database, the 15 genera covered in Stikky Trees account for 80% of the trees in the US. These 15 also account for the #1 most common tree in every state except Hawaii (we can't find hard data on what is the most common tree in Hawaii, but it may be the state tree, the kukui). And they account for the #2 tree in every state except New York (where beech is #2) and Delaware (holly). Inevitably, though, when you step outside your door, the first few trees you look at will turn out to be something else.

210: Officially, all of these are called "fruits". Anything containing a seed is a fruit. So a nut is a fruit; a tomato is a fruit; a potato is not a fruit.

212: The world's largest tree. If you are into famous trees, Wikipedia has a nice list at and there are several books including Jeff Meyer's America's Famous and Historic Trees.

223: The maps on these pages were based on several data sources, most notably those of the World Commission on Forests and Sustainable Development, You'll notice that European forests take a big hit in medieval times whereas most other deforestation happened in the last hundred years or so. In the US, about 70% of the area that was forested in 1630 (at the beginning of European settlement) is forest today. The 30% that has been converted is mainly agricultural. About three-quarters of that conversion happened in the 19th century. See

230: Top 10 species in the US. Again from research based on the Forest Service database at:

231: How trees work. (Apologies for the nutshell joke.) It is intriguing that the whole complicated contraption of a tree is a device to collect enough energy to…build the whole complicated contraption. If this seems circular to you, that's because it is.