Trees/ Tree Biology


April 1, 2018: It is refreshing in our know-it-all world to find something we didn't know about. Recently a new species of Hemlock tree was discovered on a remote island off the coast of South Korea. Now, I know that this probably isn't going to set off a tsunamis of tweets, but my heart is aflutter at the news. This new species, Tsuga ulleungensis, lives on the slopes of an inactive volcano on a tiny island and it became both the newest tree discovered in 2017 and the most endangered at the same time and already we have plans for it.

Along the spine of the Appalachians, the Eastern Hemlock is being decimated by a tiny pest called the Hemlock wooly adelgid. This tiny aphid-like creature sucks the sap from needles and it protects itself by exuding a cottony mass around its body. Just imagine thousands of Q-tips heads glued to the branches of a tree. Within a year most hemlocks die. It's a BAD problem.

Enter our new hemlock species. It's related to Japanese hemlock trees. The hemlock wooly adelgid (HWA) came from Japan (thank you kindly). The Japanese hemlock and HWA co-evolved, so Japanese hemlocks have the genetic makeup so that they're not as badly walloped as our Eastern hemlocks are. The hope is that the new hemlock species may have even more resistance genes in its DNA and that crossbreeding it with Eastern hemlock may give it some HWA protection.

Exciting, yes? Well, maybe if you're a forester or arborist. If you're the newly discovered species itself, I'm not so sure. Just imagine if you were Tsuga ulleungensis (that is if you're semi-retired and have time for such ludicrous musings). You've been standing on your volcano with your close-knit group of friends and family for millions of years and suddenly that isolation is shattered. You're discovered and the world has great plans for analyzing, breeding and propagating you. That's when I'd want to be the Howard Hughes or Greta Garbo of the plant world. I yust vant to be alone.

If there are any undiscovered species reading this, a word of warning. Lay low, keep quiet, don't be too showy or useful. We'd love to meet you, but you might not.


Feb. 16, 2017: No, that's not the title of a horror film, but it could be the title of an inspirational "Rockyesque" documentary of a once major tree that has vanished, for all practical purposes, but may have hope of beating the odds and returning. That tree is the American chestnut (Castanea dentata), not to be confused with the Chinese Chestnut or the Spanish chestnut.

Chestnut grove - pre-blightChestnut grove - pre-blightThe American chestnut (hereafter just referred to as "chestnut" to save me extra typing) was never part of the Pacific Northwest forests but was one of the dominant hardwood trees of the Appalachian mountains. There were billions (some estimate 4 billion) of them growing, some up to 120 foot heights and 8 feet or more in diameter. The mast crop of chestnuts produced were a major food source for animals and humans. Its wood was rot resistant and light weight. It was often used for furniture and you can tell a true vintage piece of furniture if you can identify chestnut as its material.

The chestnut is now classifed "functionally extinct" by the USDA. That means you cannot find a live chestnut tree anywhere (except a small handful I'll tell you about later), but you can find chestnut shrubs. So how did it go from being the dominant tree of the Appalachians to a rare to find shrub? Answer: the chestnut blight.

Somewhere around 1904, give or take a couple of years, a load of chestnut logs from Asia came into the States carrying a fungus, the chestnut blight. The Chinese chestnut is resistant to chestnut blight, developed through eons of evolutionary battle between the fungus and the tree back in Asia. Our chestnut though did not have that resistance and in the space of 40-50 years the American chestnut as a tree disappeared.

I used to be a forestry contractor in the 80's based in western North Carolina. Most of my contracts were in the southern Appalachians. What was amazing to me is I could still see in the woods these huge stumps of the chestnut that were still alive. The roots, which are not killed by the fungus, still sent up shoots. They would grow to about as about as big around as my arm and then the blight would kill them and then more shoots would arise. The chestnut would not die, even 40-50 years after the trunk was gone!

The fungus attacks the cambium, the small ring of growth tissue inside the bark, which in turn kills the Blight cankersBlight cankersbark and eventually girdles the tree which kills it. There is no preventative nor post-infection treatment to stop it. It was a killer and it couldn't be stopped. Less than a handful of isolated pockets of chestnut tree have been discovered. One pocket , found in 2006, on the Franklin Roosevelt's Little White House estate at Warm Springs caused a flurry of excitement as to whether these trees might have genes resistant to the blight or were they just isolated.

The major effort to bring the chestnut back from the dead has been focused on hybridizing it by crossing the American chestnut with the Chinese chestnut, which is resistant. This crossbreeding has been taking place since the 1930's with marginal success by the USDA. In 1983, several botanists and geneticists set up the American Chestnut Foundation (ACF)to try a different type of crossbreeding called backcrossing, where a Chinese and American chestnut are crossed and then their offspring are crossed back to the American chestnut for several generations in a row. It's slow work but has finally produced a resistant chestnut that is 15/16th's American chestnut and 1/16 Chinese chestnut. If there was AKC registration for trees it wouldn't make it but it's close.

The latest greatest news is that a genetically engineered chestnut has been developed. I can see you're thinking now, "OMG a Frankenchestnut!" But hear this out. The chestnut contains 40,000 genes. Geneticists have discovered one gene from the wheat plant that produces an enzyme which detoxifies the blight fungus. Gene spliced trees are 99.999% original American chestnut. and if you're still leery, remember that genetic engineering is happening all the time in nature. It's called evolution and it results in gene mutation (different genes) often much more profound than 1 gene out of 40,000. Hybridization leads to more gene manipulation with less control than genetic engineering

Not only are GMO chestnuts so close to being the original in genetic makeup but before these trees are even made available to the public they must stand the scrutiny of the USDA, EPA and FDA approval processes. This will be the first tree approved for genetic manipulation. When you consider all the other huge threats we have to our rural and urban forest such as Dutch Elm disease, Asian longhorned beetle, oak wilt disease, pine beetle and on and on, maybe this is a ray of hope. In a new world where biological threats can't be contained by distances it's time for a new approach to saving the old.

Several thousand hybrid trees have been replanted in the wild, but that's a long way from 4 billion. I hope to live to see Frankenchestnut emerge from the lab to the marketplace . I'll be the first to toddle out and plant one.


Dec 19, 2016: I've just finished a fascinating book, called "The Hidden Life of Trees: What They Feel, How They Communicate" written by Peter Wohlleben, a German forester. He takes some of the latest scientific research on plant communication and delivers it in a very understandable and easily readable fashion. One of the areas of research that was new to me and utterly mindboggling was that plants (or at least some of them) have to ability to taste. And that their taste palettes may be able to discern between the "saliva" of the different insect herbivores that are eating them.

It's been know for a couple of decades that plants have a very complex defense communication system. We know that some trees, such as acacia, will emit a phytochemical (plant chemical) into the air that warns other acacias that there are predators about feeding on their leaves. Other acacias then have time to prepared toxic, bitter substances in their leaves that deter feeding. One of the biggest herbivore threats to acacia in Africa is the giraffe and in the eons old battle between predator and prey, the giraffe has learned after feeding on one acacia to either move upwind of their last target or at least 100 meters away. The defense aroma can't tip off those unsuspecting acacias.

What's more recent is that botanists, or more specifically chemical ecologists, believe that some plants may be able to identify who is attacking them. There are two possible ways they may do that. By recognizing the saliva of the herbivorous insect or by recognizing the vibration patterns of the leaf munching of that insect. Why does a plant care what's feeding on it? This is what is truly evolutionary genius.

The acacia I mentioned above doesn't distinguish between whether it's a giraffe or whether it's a caterpillar. It's reaction and those of its buddies close enough to "smell" is to produce bitter toxins in their leaves. That requires a fair bit of energy to do on the part of the plant. What if a plant could instead enlist others to protect it? Maybe other insects that will feed on the insects that are feeding on them?

That's what some elms and pines . . . and brussel sprouts do. They are able to detect the species that isSawfly parasitic waspSawfly parasitic wasp feeding on them and then secrete a fragrance that attracts a tiny parasitic wasp that then attacks the attackers. The parasite - host relationship is very species specific, so the leaves must produce a very specific fragrance that only attracts the specific parasitic wasp for that attacker. If another species attacks then it has got to produce a different fragrance to attract a different beneficial parasite or predator. The advantage is that the plant is not taking up a lot its time and energy building up defensive chemicals in it's leaves. The disadvantage is that there are a limited number of fragrance options. Over evolutionary time the fragrance palette develop to the most commonly occurring attacking species. Get a new species in the area or environmental pressures cause a minor pest to become a major pest and there's no alarm fragrance for it.

Again, for every plant defense strategy its predators try to develop a counter strategy and it's been found that some species of caterpillars secrete a enzyme inhibitor when feeding that masks the true nature of its saliva. Copenhagen for insects.

For more detailed information, I highly recommend ( and I absolutely love the title of this article!) '"The Silent Scream of the Lima Bean" from the Max Planck Institute of Chemical Ecology. Google it.
As with all good research the attempts to unravel mysteries lead to the exhumation of many more. For instance, if plants can taste the saliva of different predators does that mean they have a memory? Don't ask me. To quote the Great Bard, "There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy."

And hey, the next time your kid turns up their nose when you serve them brussel sprouts . . . there might just be a perfectly good phytochemical reason.


Oct 16, 2016: It's the morning after a big storm here in NW Oregon. This early in the fall and with many of the deciduous trees still in leaf, there's going to be a lot of downed trees and branches. If you're one of the hapless souls in Oregon that has had tree damage in your yard, you may be looking for emergency tree work.

A WORD OF CAUTION, only hire LICENSED tree services. Major storms not only mean lots of work for tree companies but it also spawns a small host of what I call "pirates with chainsaws' that troll storm damaged communities looking to stop and offer their services. It's often a "great deal" they're offering because they just so happen to be in your area doing other work.

So why is it important to hire a licensed company in Oregon? By "licensed" I mean a company that shows a license number on their truck with the prefix "CCB" or "LCB". Those prefixes stand for Construction Contractor's Board and Landscape Contractor's Board respectively. Companies licensed by one of the two agencies are required to post their number on all their advertising (truck, business cards, ads, etc) and to be licensed they must annually post a bond and show proof of current liability and worker's compensation insurance. It is illegal in the State of Oregon to perform tree work (unless its logging) without licensing.

Now before you get your libertarian hackles up about yet more government interference with the free enterprise system, let me tell you that licensing is in place to protect the consumer. Since a company is required to post a bond, it means that if you have a claim against that company for negligent or non-performance or breach of contract, you can submit a claim to their licensing agency and it will be reviewed by a board and, if the claim is warranted, monetary damages from their bond is awarded. The claims process is a free service to consumers (paid for by licensee fees). Without it you would be forced to go to court, which we all know is not a free process.

The fact that all licensed companies must have liability insurance means that if a tree company is trying to get a tree off your roof and drops a chunk of wood through the window of your Porsche or Yugo, then the insurance will cover the damage.

All licensed companies must have worker's compensation, the insurance that covers workers injured on the job site, which might be your yard at the time. Worker's injured without worker's comp in your yard can sue you, the homeowner, for their medical bills and any subsequent support. You may end up selling your home to pay for the care of a pirate without a chainsaw in a wheelchair.

If you google Oregon CCB or Oregon LCB, their websites have license search pages by which you can search for licensed companies or if a company is licensed. Most tree services are licensed with the CCB, a few with the LCB. A note: CCB licensed companies can do everything when it comes to trees except plant trees. LCB licensed companies can do everything. But when you're tree is resting upside your house, you're probably not thinking of planting right away.

Now you know the difference between licensed tree companies and the unlicensed pirates. If you choose the pirate, beware the financial plank you walk.


August 12, 2016:

"If trees could scream, would we be so cavalier about cutting them down? We might. If they screamed all the time for no good reason" Jack Handey, Deep Thoughts, 1992.

Humorist Jack Handey probably wasn't aware that recently we've discovered that trees do scream, in a manner of speaking, and communicate and share in other ways. This isn't some new age, drum circle, tree hugging crap, this is now hard science. Over the past three decades, research has been showing that plants (not just trees) can communicate to other plants (even species not their own) both aboveground and below ground.

Aboveground, research has found that some plants ( and probably a whole lot as current research is just scratching the surface) communicate distress, which is usually an insect or herbivore animal feeding on them. They do so by emitting an odorous complex of compounds called VOC's, or volatile organic compounds. Other plants sense these VOC's and in turn may generate more of their own chemical compounds internally that are repellent or toxic to herbivores. As omnivores, we have some passing familiarity with some of these compounds such as: nicotine, caffeine, cocaine, morphine, quinine, menthol, camphor, cannabinoids and a gob of others. The level of these compounds can fluctuate in plants dependent upon the threat level the plant senses.

In addition to internally manufacturing defensive chemicals, some plants will also emit their own VOC's that either repel herbivores (usually insects) or attract the predators of the insect attacking them. The plant version of a mace/rape whistle.

Oddly enough, the unburned fuel from car tailpipes also produce VOC's which contribute to increased ozone. While clean air laws have lowered VOC induced ozone in some places, trees have increased their VOC induced ozone. Go figure. I can't.

How plants communicate underground is a newer discovery and it relates to plants in communities, or for the purpose of this article, trees in a forest community. The roots of forest trees can extend many times beyond the crown of the tree, so they are in the close proximity to the roots of many other trees and plants. What really connects all these individual plant roots is a group of fungi called mycorrhizae. Mycorrhizae colonize the roots of plants and live symbiotically. They obtain food from their host and in turn they extend the roots exposure and ability to absorb water and nutrients.

These fungi form a vast interconnected web with tree roots which has been dubbed "The Wood Wide Web" . Trees have been found to communicate distress situations similar to aboveground VOC's. What is really amazing is that this WWW has been found to be a pipeline by which other trees will share food resources, both with their same species and . . . with other species. So contrary to the long held Darwinistic belief that it's the survival of the fittest in jungle or forest, it's instead appearing to be more like a peace and love commune.

One forest ecologist, Suzanne Simard, has identified what are called "Mother Trees". These are larger older trees in a forest that act as the nexus points of the wood wide web. When they are cut down, it's like when a computer server goes down. Resource (in this case carbon) sharing ends and it substantially lowers the survival rate of younger trees in their proximity. It may argue for a whole different perspective on forest management.

All this talk about plants talking and screaming and sharing that makes me and others feel all warm and fuzzy might help people be aware of how truly amazing trees (and plants) are, but it may not be helpful in truly understanding. As one forest ecologist says, we need to stop anthropomorphizing plants and start phytomorphizing ourselves to understand them. . . .I gotta go look that up.

F & P