Visiting a forest can induce a significant increase in both the number and activity of natural killer cells, one of the ways our body fights off cancer. Can the aroma of wood essential oils replicate the immune-boosting effects of walking in a forest? Forest bathing is a term coined in Japan in the 1980s. Since then, we have learned it has benefits beyond just the exercise. In this video Dr. Greger looks at some of those benefits, and whether or not you need to actually visit a forest to experience them.

Friday Favorites: Boosting Anticancer Natural Killer Cell Function with Forest Bathing (nutritionfacts.org)

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Intro: Forest bathing is a term coined in Japan in the 1980s. Since then, we have learned it has benefits beyond just the exercise. In this video I look at some of those benefits, and whether or not you need to actually visit a forest to experience them.

Previously, I showed how exposure to nature can have self-reported psychological benefits, but there was a dearth of data on changes in objective measurements. So, I was excited to see this paper on the effects on levels of the stress hormone cortisol in the saliva of those partaking in “forest bathing”––which just means visiting a forest and surrounding yourself by trees.

The level of cortisol in your saliva is considered an indicator of your stress level, and after walking in a forest, compared to walking in a city, or even after just hanging out in a forest compared to a city, people’s salivary cortisol levels were significantly lower. But wait a second, the same effect was found before they went to the forest. Huh? Forest bathing was associated with significantly lower salivary cortisol both before and after, compared with visiting an urban area. Therefore, it appears that just the thought of going to spend the day in the forest relieved stress. So, when comparing the effects of forest bathing versus urban visiting, the anticipation placebo effect may play a more important role in influencing stress levels than the actual experience of being in the forest. So, I was ready to dismiss it as just another nebulous psychological effect until I read this. Studies on the effects of forest bathing on the immune function showed that visiting a forest can induce a significant increase in the number and activity of natural killer cells––one of the ways our body fights off cancer. That got my attention.

It all started with this study. Twelve men were taken on a long weekend to walk in some forests, and almost all of the subjects (11 out of 12) showed higher natural killer cell activity after the trip––and not just a little; about a 50 percent increase compared to before the trip. Now, just exercise can affect immune function, but they weren’t walking any extra; they were just walking in a forest instead. Yeah, but they also were taken on a trip somewhere, introducing other variables. So, how about randomizing them to go on some city trip versus the forest trip? And if there is some special forest effect, how long does the effect last? Do you have to, like, walk in the forest every day? Before jumping into all that, how about we first see if it works in women too?

Same kind of setup, and same results: a significant boost in natural killer cell activity walking around in the woods. And this time, they went back a week later to retest them, and they were still up––though after a month, they came back down. But hey, once a week should do it. But it was a multiple-day trip. Who has time to hang out in forests all weekend, every weekend? How about just a little day trip? The title gives it all away. Boom! Same thing! The same big jump measured the day after the trip, compared to before, and with the same staying power. Natural killer cell activity still boosted a week later. This suggests that if people visit a suburban forest park once a week on a day trip, they may be able to maintain the increased anti-cancer immunity.

Okay, but I’m still not convinced. How can you attribute the benefit to the forest itself, when all you have is before and after data? To make the case that nature had anything to do with it, you’d need a control group that took the same kind of trip but went to somewhere else instead. And…here we go. It turns out visiting a forest, but not a city, increases human natural killer activity. Here’s the forest data, just like before, but nothing on a trip to go walking in a city. By the end of the forest trip, 80 percent of the subjects experienced a boost, compared to only 1 in 10 of the city walkers.

And, both trips were matched for physical activity, and alcohol, and sleep—other things that can affect immune function. And so, here we go. Confirmation of boosted immunity––but only on the forest trip, “indicating that forest bathing does indeed enhance [natural killer cell] activity.” Moreover, they found that the increased activity lasted up to 30 days after the trip. Check it out. Still up a week later, and even a bit up a month later. “This suggests that if people visit a forest once a month, they may be able to maintain increased [natural killer cell] activity.”

Okay, so, now that we know that it’s a real effect, the next question is, why? What is it about forests that gives us the boost? And (you can imagine Big Pharma thinking), can you make it into a pill? We’ll find out, next.

Studies on the effects of “forest bathing,” a traditional practice in Japan of visiting a forest and breathing its air, have found it “can induce…significant increase[s] in the number and activity of natural killer cells” that can last for as long as a month. And, because natural killer cells are one of the ways your body fights cancer (by killing off tumor cells), the findings suggest that forest visits “may have a preventive effect on cancer generation and progression.” Okay, but how? “Why did the forest environment increase…natural killer cell activity?” What is it about the forest environment?

One thought is that the boost may be related to a reduction in stress. If you measure the amount of adrenaline flowing through people’s systems, did hanging out in a forest—but not a city—drop adrenaline levels down? Yes; so that checks out, but drip some adrenaline on human blood cells in a petri dish, and there does not appear to be any effect. The stress hormone cortisol, on the other hand, dramatically suppresses natural killer cell activity. So, maybe the forest led to less stress; less cortisol, which released the natural killer cells under its thumb––and you get the big boost?

We know being surrounded by nature can decrease levels of cortisol in our saliva, but what about our bloodstream? A significant drop after a single day trip to the forest. But a week later, the cortisol was normalizing, and the forest effects sometimes appeared to last an entire month. Anything else that could cause a longer-term immune system change?

Maybe we’ve been missing some of our “Old Friends.” If you sample outdoor air, you can pick up an abundance of microorganisms floating around from the soil or water, which are absent in our indoor air (which is dominated by organisms that either live on us or try to attack us). So, maybe on a day-to-day basis, in terms of keeping our immune system on ready alert, it might not be sufficient to encounter only the biased microbes of the modern synthetic indoor environment that lacks some of the Old Friends, and probably bears little resemblance to the microbes we evolved to live with over millions of years.

Or, maybe it’s the plants themselves. Maybe it’s the aroma of the forest? Trees produce aromatic volatile compounds called phytoncides, like pinene, which you can breathe into your lungs in the forest. But do these compounds actually get into your bloodstream? One hour in the woods, and you get like a six-fold increase in circulating pinene levels circulating throughout your system. Okay, but to fully connect all the dots, the phytoncides like pinene, these tree essential oils, would have to then induce human natural killer cell activity. And…guess what? Phytoncides induce human natural killer cell activity. If you stick natural killer cells in a petri dish with some unsuspecting leukemia cells, your killers can wipe out some of the cancer cells; but add a whiff of cypress, white cedar, eucalyptus, or pine, and the cancer cells don’t stand a chance.

A combination of wood aromas improved the recovery of mice put through the wringer. But this is the study I was looking for. If we want to know if the magic ingredient is the fragrance of the forest, then let’s see if we can get that same boost in natural killer cell activity just vaporizing some essential oil from one of the trees into a hotel room overnight. And it worked! A significant boost in natural killer cell activity; though it just boosted their activity, rather than their number, and being in the actual forest can do both. So, maybe it’s a combination of the tree fragrance and the lower cortisol levels working together?

Ironically, these phytoncide compounds are part of the tree’s own immune system, which we may be able to commandeer. The researchers speculate these compounds may be playing some role in the fact that more heavily forested regions in Japan appeared to have lower death rates from breast cancer and prostate cancer. Being out in nature has been found to be an “important coping strategy among cancer patients.” It turns out this could potentially be helping more than just with the coping, thanks to the fragrance of trees.

The Texas Tree Climbing Competition will be held at Richard Moya Park southeast of Austin, Texas. Gear check will be May 18th and the competition will be May 19-20, 2023.

The competition aims to simulate working conditions of arborists in the field. Male and female competitors perform five different events during preliminary rounds. Each event tests a competitor’s ability to professionally, and safely maneuver in a tree while performing work-related tree-care tasks in a timely manner.

Come compete or just to watch!

Texas Tree Climbing Championship | ISA Texas Chapter

Third times a charm.  I have officially registered for the 2023 Tour des Trees Reno!  The ride will start in Reno, Nevada, past Lake Tahoe and head into Northern California. Michelle and I are very excited to see what this years ride has in store for us.  I humbly ask that you please consider donating to my fundraising campaign to support tree education and research.  Any amount helps.  Please feel free to share the links below with family or friends who might be interested.  My fundraising page will be open until the end of October.  If you have any questions, please feel free to contact me.  Thanks again for your time.  Stay healthy and safe.

Link to my fundraising page:

https://tour-des-trees-2023.blackbaud-sites.com/fundraising/herminios-tdt-2023-fundraising-page

Ice storms are serious business for Texas trees.  If you are a homeowner that would like to know how to handle storm damaged trees, click here and click here.  Click here to see if your damaged trees covered by insurance. If you are a tree professional, the Texas Chapter has two on-demand webinars from the ice storm in 2021. You can view them here to learn from Texas experts on how trees respond and how to treat them.

Texas Gov. Greg Abbott has received the full amount of the lawsuit settlement from the 1984 accident that put him in a wheelchair — $8.9 million.

Abbott, 65, was the state’s attorney general in 2013 and running for his first term as governor when he decided to voluntarily release copies of the September 1986 agreement to the media. He won a third term as governor in November.

He was 26 at the time of the incident when he went for an afternoon jog on a windy day through River Oaks in Houston. A limb snapped off a large oak tree as he was passing under it, crushing his spine and damaging his kidneys.

Abbott sued the homeowner and tree care company and won a settlement, which shows tax-free annuities in graduated payments. The payments began with a $300,000 check in 1986. They include both monthly payments that will continue for the rest of his life and lump sums that are deposited every three years until the final one last year.

 

Read the rest of the story here in the Dallas Morning News

 

Mistletoe may be a welcome holiday sight when hung over a doorway if a loved one is near. But it can be an unwelcome intruder when found in your trees, according to a Texas A&M AgriLife Extension Service horticulturist.

“Mistletoe is a hemiparasite – a semi-parasitic plant,” said Allison Watkins, AgriLife Extension horticulturist for Tom Green County. “It makes its food from photosynthesis, but the roots grow into the host tree, sucking water and minerals out from the sap.”

In other words, you likely do not want to see mistletoe growing on your favorite shade tree or prized ornamental. However, mistletoe can survive as long as the tree it inhabits. So, some mistletoe alive today may still be around in 100 years.

One type of mistletoe you commonly see used as decoration over the holidays is in the family Phoradendron, which appropriately translates to “thief of the tree” in Greek. Mistletoe has been used across various cultures throughout history for everything from warding off demons from entering a doorway to protecting babies from being stolen from their cribs in the night by fairies.

Although mistletoe is called the kissing plant, its name may have originated from Old English for the words for twig and dung. How’s that to get you in the romantic holiday spirit?

The Issues With Mistletoe

Mistletoe causes tree stress and can make a tree more susceptible to diseases and insects, Watkins said. Although unlikely to kill a healthy tree, it can cause limbs to die. It can be especially hard on a tree during drought.

Mistletoe easily spreads as birds eat the berries and then spread the seed from limb to limb and tree to tree through their feces. The seeds are exceptionally sticky and may also hitchhike on their feet and beaks.

Certain species of mistletoe can also shoot out their own seeds at speeds around 60 mph once the berry bursts like an overfilled water balloon.

Some mistletoe is poisonous, so it is always wise to use care when handling the plant. Different parts of the plant and different species have varying levels of toxicity. And while birds and wildlife eat the berries, it isn’t something you want your family members, including pets, to ingest.

How To Identify Mistletoe In Nature

Mistletoe is most easily spotted in winter when many of the host trees lose their leaves to reveal clusters of the evergreen mistletoe. The spherical shape can be as large as several feet across.

Since birds like to perch in the tops of high trees, mistletoe is most often found in mature trees near the crown. A tree branch may be enlarged where the plant has attached itself.

In Texas, the type of mistletoe you’ll find on trees typically has white berries in clusters. Although we mostly find mistletoe in our region on deciduous trees, like oak and mesquite, the plant’s 1,000-plus species around the world have adapted to survive on everything from cacti to pines.

A Friend To Forests, Pollinators And Woodland Creatures

Mistletoe plays a key role in many woodland and range ecosystems. For example, its white flowers provide nectar and pollen for native bees and honeybees. There are also several types of butterflies and moths that rely solely on mistletoe species as host plants for their caterpillars.

“Birds aren’t the only animals that munch on mistletoe – squirrels will also eat the berries, and deer and porcupines will eat the plant itself, especially if other food is scarce,” said Maureen Frank, Ph.D., AgriLife Extension wildlife specialist, Uvalde.

Many animals nest in clumps of mistletoe, especially when the plant causes its host tree to form witches’ brooms, which are dense masses of distorted branches, Frank said. Mistletoe and the corresponding witches’ brooms are used for shelter by tree squirrels, flying squirrels and a variety of birds, from tiny chickadees to raptors like Cooper’s hawks.

The damage done to trees by mistletoe can also provide homes for cavity-nesting species of birds, bats, insects and small mammals.

Should You Remove Your Mistletoe?

“Even if you remove mistletoe from a tree, the root-like structure remains embedded in the tree, meaning it will grow back,” Watkins said.

Although no herbicide can kill mistletoe without harming the tree, one plant growth regulator called ethephon, Florel Fruit Eliminator, is registered in the U.S. to control the growth of mistletoe on deciduous trees, she said.

The only way to eliminate mistletoe from a tree is to prune the branch it is on. If you feel like your tree is becoming overwhelmed with the parasite, keep in mind that mistletoe takes two to three years to mature so the sooner you can remove the infected branch, then the better you minimize spread. And the smaller the branch that must be removed, then the less stress on the tree.

“In most well-maintained landscapes, there may be mistletoe here or there but it’s probably not something to worry about too much,” Watkins said.

The stress from over-pruning could be more damaging than the mistletoe itself, she said. Watkins said to keep these tips in mind if you do decide to prune:

For more information on mistletoe, visit Forest Health: Mistletoe by Texas A&M Forest Service.

What to do with fallen leaves

COLLEGE STATION, Texas — Even though it’s the Christmas season, autumn is still here and leaves are continuing to fall across the state, building up and around our homes and yards.

Fallen leaves have many benefits to our ecosystem when left alone but can also become a wildfire hazard if they remain in the wrong places. Which creates the question, what should we do with fallen leaves?

The key to leaves around your home is finding the balance between removing and leaving them.

Embers are the leading cause of homes destroyed by wildfires, and embers can gather where leaves have fallen around your home. That’s why removing leaves on and near your home can help reduce your risk to wildfire.

According to Kari Hines, Texas A&M Forest Service Firewise Coordinator, homes should be cleared of fuel buildup, or debris, from zero to five feet away. Homeowners should also decrease the fuel buildup next to wooden attachments.

“Leaves should be removed from these first five feet, usually the gutters, the garden beds that touch the home and where leaves gather up against wooden fences and wooden decks,” said Hines. “If you choose to leave leaves in your yard, which we recommend, do so in a place that is not in one of these vulnerable locations.”

So, why keep leaves in your yard at all? Leaving leaves where they fall can provide the most benefit to your yard, trees and overall ecosystem.

“We recommend leaving leaves where they are because it mimics the forest and a natural setting,” said Matt Weaver, Texas A&M Forest Service Urban Forester. “If you look at the forest floor, it’s leaves. Over time, those leaves break down and become organic material and eventually the soil itself.”

This is especially important in urban settings, Weaver said.

“In urban areas, there are a lot of soil issues like compaction, and that organic material is actually really important for tree health,” said Weaver. “Most of the soil in urban areas is lacking organic materials and the only thing to help with that is mulch, which can be leaves.”

Leaves can be used as mulch to also insulate and protect the roots of trees and plants from cold weather.

“Leaves also provide food and shelter to many insects and organisms that help keep our soil healthy,” said Hines. “By leaving leaves, you are leaving the insects that are overwintering in that thermal protection layer, you’re returning organic material to your soil.”

If you want to reduce long-term yard maintenance while still providing some benefit to insects in your yard, you can use a mulching attachment to mulch the leaves in place soon after leaves fall, but don’t wait too long or you risk mulching the beneficial insects.

The smaller pieces will be less likely to blow away in the wind, while still offering some shelter to overwintering insects. The smaller pieces will also decompose easier, speeding up nutrient cycling and allowing your trees to use the nutrients quicker.

The other option, removing leaves completely, while less desirable, can be done by making a compost pile, burning or discarding of leaves in a biodegradable container. Composting leaves is a good way to cycle those nutrients back into the soil as it is a good natural fertilizer for gardens and flowerbeds.

If you choose to burn your leaves, use safe debris burning practices: keep your piles small, clear flammable materials away from your piles, follow all local burning restrictions and avoid burning on dry, windy days.

Though leaving leaves will require some work throughout the winter to keep windblown leaves from building up around your house, the benefits they provide are invaluable. Find the balance of leaves in your yard this season to help keep it safe from wildfires and provide environmental benefits.

###

Texas A&M Forest Service contacts:

Kari Hines, Firewise Program Coordinator, 512-375-0354, khines@tfs.tamu.edu

Matt Weaver, Urban Forester, 713-688-8931, mweaver@tfs.tamu.edu

Communications Office, 979-458-6605, newsmedia@tfs.tamu.edu

You may have heard the saying, often credited to a Chinese proverb, that the best time to plant a tree was 20 years ago, and the second-best time is now.

What’s less well-known is how to choose the best tree and the best site in your landscape to ensure years of enjoyment.

Putting the right tree in the right place will help avoid future problems and bolster the benefits the tree provides over its lifetime. Those benefits include providing shade for energy conservation, increasing property values, reducing stormwater runoff, providing habitat for wildlife and enhancing quality of life.

The best time to plant trees in Texas is November through early spring, and a little research before planting will increase your chances of long-term success.

The first thing to do before you plant is to look at the area where the tree would be growing, taking into consideration any obstructions as well as the type of soil in the area.

“Before you even decide what tree you want, when you’re thinking about planting a tree, look at your site,” said Mickey Merritt, Texas A&M Forest Service Urban and Community Forestry Program Leader. “How large is the site? What kind of tree will it support at maturity? Look for any safety issues. Where are the utilities located? Are electric lines overhead or underground?”

The wrong tree or an inappropriate site can be detrimental to property values and can lead to other problems and even safety issues.

“If you plant the wrong tree in the wrong spot, it could lead to all kinds of problems, including tree instability, structural failure, damage to sidewalks, driveways or underground utility lines, as well as blocking lines of site and obstruction of signage if planted close to a street,” Merritt said. “The tree won’t be allowed to reach its potential, which in turn stresses and weakens the tree.”

Once you’ve established the location, the type of new tree you’re adding can be determined by looking at why you’re planting it and what it will contribute to the site.

“What do you want that tree to provide? Do you want fall color, flowers, wildlife benefits, energy conservation? Do you want it to frame a view?” Merritt said. “Thinking about your reason for planting will help you decide what kind of tree you want.”

Establishing the purpose for planting the tree will help when considering other factors, including the size and shape of the tree at maturity and whether it will fit the design and layout of your property.

Other things to keep in mind include the amount of sun and water available in the planting location, the type of soil and the area available for the roots. Small trees need about 400 cubic feet of soil, and large trees may need more than 1,200 cubic feet of soil area at maturity.

Merritt said trees native to the area are usually the best option.

“They have evolved within the area, they handle the weather patterns and conditions better, they generally live longer and are healthier, are less prone to attack by pests and they provide more benefit to wildlife,” he said.

Across Texas, different tree species thrive in different regions. In the central part of the state, Texas Mountain Laurel, Lacey Oak and Mexican Sycamore are generally good options. In the Dallas-Fort Worth area, American Smoketree, Bigtooth Maple and Ginkgo tend to do well. And in East Texas, in addition to pine trees, Eastern Hophornbeam, Pawpaw and Black Walnut trees are popular.

Invasive trees should be avoided because they decrease biodiversity by threatening the survival of native plants and animals.

For help finding the best trees for your region of the state, visit the Texas Tree Planting Guide at https://texastreeplanting.tamu.edu.

####

Texas A&M Forest Service Contacts:
Mickey Merritt, Texas A&M Forest Service Urban and Community Forestry Program Leader, 713-562-6469, mmerritt@tfs.tamu.edu
Texas A&M Forest Service Communications Office, 979-458-6066, newsmedia@tfs.tamu.edu

 

Join in the Texas Arbor Day celebration here: https://tfsweb.tamu.edu/arborday/ 

Landscape Plants for the South-Central United States is a resource for students, Green Industry professionals, and serious gardeners interested in designing and maintaining sustainable built environments.

The heart of the book is extensive discussions of hundreds of taxa of native and introduced landscape plants. To facilitate selection during design, plants are arranged in their predominant landscape use categories, rather than in botanic families or alphabetical order.

For each main taxa, we provide detailed identification characteristics, plant habit, growth characteristics, cultural requirements, regions of adaptation, aesthetic and ecosystem assets that the taxon can bring to designs for built environments, typical modes of utilization, liabilities and limitations potentially associated with the plant, plant origins, etymologies, and socio or economic importance.

Numerous related taxa are also included. Over a thousand black and white images and line drawings enrich the text throughout and 140 pages of color images are included in plates following each section of the book.

Following up the plant discussions is an extensive glossary of morphological, biological, and cultural terminology, including notations on key diseases and pests mentioned in the text. A master list of references provides a starting point for further studies. An index of all scientific (accepted, synonymous, and misapplied) and common names of plant taxa facilitates plant sleuthing when only a common name or out-of-date scientific name is known.