Saturday, June 27, 2009

Dead bluebirds in shelters.

The other day the following email crossed my screen.


Today(Th., 06/25/'09), I found another dead bluebird in one of our cone shelters at Raystown. It must have died a horrible death.

The Raystown folk are looking at getting mesh covers for the cone shelters. This is dead bluebird#02 and other bluebirds have been rescued out of the cone shelters. I encourage everyone to keep their shelters wide and I discourage the use of cone shelters without mesh covers. For some reason, bluebirds like to go down into the cone shelters. They don't realize the peril.

--Rick Entrekin
Huntingdon, PA.

Plantra responded with the following offer.

Plantra will supply free nets to anyone who requests them for any brand of tube. This is an important topic.

Yes, this is an important topic and I want fill in some history, offer some alternative solutions and ask for any ideas others might have for ways to keep bluebirds out of tree tubes without interfering with tree growth.

At the risk of giving away the ending, we are now recommending installing Plantra tree tubes with stakes on the inside so the birds just walk out.

In 1989, we had the first reports of bluebirds in tubes. (I co-founded Treessentials. We sold Tubex brand.) Other species also end up in tree tubes, but bluebirds do so more than others and since bluebirds suffered significant population loss, losing a single bird is a tragedy to avoid.

The first place we went looking for help was the foreign manufacturer. Initially, they denied experiencing any problems in the UK and treated us as though we were over-reacting. They were no help at first. Later, we learned they knew of the problem. Even The Royal Society for Protection of Birds knew.

Much to my surprise there was the equivalent of a gentleman’s agreement to ignore bird death in tubes. They suppressed the problem by reasoning the tree tubes were creating needed habitat for birds to use for centuries to come. The sacrifice of a few birds was a price worth paying.

I believe they were afraid that if the public knew, there would be an outcry against tubes and tree tubes were the only effective method of ensuring the establishment of young trees in the English forest. Believe it or not, in the UK over half of all broadleaved oaks and other hardwoods are planted with four or five foot tree tubes. The reason is that they do not tolerate planting failure. They expect every tree they plant to live and provide the protection required to get the job done. Why would anyone do any less? Tubex tubes sold in America were the first to supply a free net with every tube 4 feet and over. That policy continues to this day.

From a strictly biological perspective, I cannot argue with the logic of ‘sacrificing’ a few birds for the long-term benefit of the entire bird population, but we will never be satisfied with that solution.

Once it became obvious this was a serious problem and we were not going to get help from overseas, we had to find our own solution. With great trepidation, I called Sadie Dorber who was then president of the North American Blue Bird Society (NABS). Sadie listened carefully as I described how we introduced treeshelters to the US to protect oak seedlings from deer and generally ensure a future for oaks in America. She well understood the problems of plants and animals that evolved survival skills in habitat that no longer exists. She listened and to my surprise was very understanding. Sadie agreed there was a serious problem and offered her help. Bluebirds were dying needlessly in tree tubes.

Sadie told me they had a similar problem with the ventstacks on tobacco drying sheds. The solution was a simple wire mesh over the opening. Sadie put us in touch with Jack Finch. Jack had started the non-profit corporation Homes for Bluebirds, Inc. to distribute bluebird boxes. Jack was known nationally and Dan Rather had recently profiled his efforts. Jack Finch was the “go to” guy for bluebird problems. He once built a pit under bluebird nesting boxes and filled it with snakes to develop methods to keep snakes out of the nest boxes he was producing.

We sent Jack some tree tubes. Chris Siems, one of my two partners at Plantra and the first employee of Treessentials remembers how Jack set up his test.
“He put a wood slat across the top of the tube to reduce the opening size and prevent accidental entry (falling in) by birds, then attached the tubes to stakes so the bottom of the tube was 2-3’ off the ground, and attached a collection bag to the bottom on the tubes. He monitored the tubes/bags hourly, and captured bluebirds in the bags – meaning that the birds had to be trying to get into the tubes rather than falling in.”

Based on Jack’s tests, we decided to exclude the birds. Flexible mesh tubes slipped over the top were the easiest solution. We began supplying a free flexible mesh with every tube four feet and taller. We have not had much trouble with shorter tubes. I am somewhat surprised by the incident mentioned in the email at the beginning since it was in a shorter conical tube. It is rare to hear of a bluebird in a shorter tube.

There are additional theories for why bluebirds enter tree tubes.
  1. Jack Finch’s explanation is that bluebirds are cavity nesters and tubes are attractive cavities.
  2. Some folks say bluebirds eat bugs and enter the tube in pursuit of dinner.
  3. I think some bluebirds actually fall into the tubes

Elements of all three might be true. Let us explore each reason

1. Bluebirds are cavity nesters and tree tube openings trigger an instinct to explore cavities even though the cavity faces the sky.

This seems odd in the sense that we expect a nesting cavity opening to be perpendicular to the ground, not open to the sky and rain the way a tree tube does. The instinct to explore cavities probably does not have an orientation requirement since tree cavities facing the sky can be quite spacious and provide adequate cover.

To my surprise, the NABS FAQ page has an entry near the bottom about open top nesting boxes. This style is discouraged because the nestlings get wet and die of hypothermia. The important point here is that the bluebirds nested in a box with a top open to the elements. That fact strongly supports Mr. Finch’s explanation the birds are looking for a nesting site when entering vent pipes and tree tubes. Even if unwise, cavities open to the sky are acceptable to the bird.

It could be that the ideal nest height triggers the instinct to explore a cavity. NABS says bluebirds will tolerate a nest as low as three feet, but prefer 4 or 5 feet. The bluebirdsforever website says: “The bottom of the nest box should be at least 3 feet above ground. Ideally, it should be mounted 4 to 5 feet above ground.” The reason given is that anything lower is more susceptible to predators. This strongly parallels our experience with tree tubes. Dead bluebirds are found in 4 and 5-foot tall tree tubes and rarely 3 foot. In over twenty years, I do not recall a single instance of a bluebird in a tube shorter than 3 feet.

Jack Finch’s explanation of birds looking for nesting sites probably covers the vast majority of cases. There are two other possibilities often put forth that may explain some cases.
2. Bluebirds eat bugs and enter the tube in pursuit of dinner.

According to insects make up 80% of the bluebird diet during spring and summer. A University of Michigan site states: Eastern bluebirds eat a variety of foods depending on the season. In summer months, eastern bluebirds consume mostly beetles (order Coleoptera), crickets, caterpillars, grasshoppers, and other insects. These are exactly the sort of insects found crawling on a leaf in a tree tube.

Given the obvious fact that bluebirds have no fear of entering a tree tube, it seems plausible a bluebird would drop into a tube to grab a beetle.

3. Bluebirds fall into the tubes

It is hard to imagine a bird falling into a tube. Still, we have all seen wildlife videos of botched landings by birds. (Click the link to the left and watch the video if you think birds always land perfectly) The tree tube in a field is a suitable perching structure and thereby creates bluebird habitat. The tree tubes become convenient perches from which to pursue flying insects or swoop down to the ground and grab a grasshopper. The hunting bird takes off and lands hundreds of times in a day. Not all landings are perfect and some tree tube designs make landing riskier.

The bluebird has three toes forward and one toe back somewhat like a thumb. Think of the rear toe as analogous to the tailhook on a jet landing on an aircraft carrier. If the tailhook misses the arresting wire, the plane hurtles forward and must take off or fall into the sea. Perching birds evolved to land on round twiggy branches covered with soft bark. The classic Tubex tube has a hard surface with a flair curved like a funnel into the tube.

When landing on a flared hard plastic rim the three forward toes have nothing to grab and can slide forward. To land successfully the rear-facing toe must catch the edge of the hard rim flare. If the single rear toe slips, the downward momentum of the bird will pitch it head first into the tube. Once in the tube it cannot open its wings to fly out and it cannot walk up the smooth inside.

This happened very quickly, but I remember standing in a field and saw a bluebird land on the tube rim and pitch forward into the tube. At least that is what I thought I saw. In retrospect, I might have been witnessing a nest search, a bug pursuit or a botched landing. Whatever I saw we have to keep the birds out of the tubes.

Soft un-flared rim
Plantra tubes are made with soft low density polyethylene (LDPE). Since it is soft, it does not abrade tree bark. The Plantra tree tube does not need a bird sucking flare in the rim. You can bend or roll up an LDPE tube without damage. The softer more flexible rim might allow the claws a better and safer grip. The nested style tubes are made with a similar but hard plastic called polypropylene (PP). PP tubes resist bending and turn white if forced to bend. I think eliminating the hard curved rim helps, but it is not the complete answer. Some customers report fewer bird problems with Plantra tubes, but birds still enter our tubes. Eliminating the flare is not a complete solution.

Pinch the top mostly closed

Inch and a half entrance holes are recommended by NABS for eastern bluebird nesting boxes. That means the opening at the top should be smaller than 1.5 inches to exclude bluebirds.

This should only be attempted with a ventilated tree tube. Without ventilation, the unchecked photosynthesis in a tree tube depletes CO2 below the level photosynthesis needs to keep growing. Also without ventilation, moisture levels in the tube reach levels that cause fungal problems in some plants.

There are some other potential benefits of this approach. Birds do what birds do. We have seen cases where a tube becomes an extremely popular perch and the plant and tube become encrusted in feces. Any fertilization effect is lost if the plant becomes coated. The small opening should limit the amount of feces deposited in a tube.

Additionally, this configuration may produce a straighter stem. The apical meristem or terminal bud seeks blue light. For this reason, we make the sidewalls red to suppress branching in the tube and channel growth toward the blue light that naturally propagates down the tube from the strongly blue middle of the sky. The reduced opening at the top will create a smaller and more focused source of blue light for the terminal bud to aim for. I am speculating here, but that might create a straighter stem.

Put the stake on the inside of the tube.

Sadly, we find many growers do not use the mesh. Recently we have been working on another approach to prevent bluebird death. There is a video on youtube of birds in the UK nesting in a tree tube and walking up and out at will because the tree has emerged. Birds know how to walk up a tree stem. We always knew the problem went away once the tree emerged. This led to an obvious idea. Put the stake on the inside and the birds can walk out. So far, this seems to be working.

Traditionally, we have recommended putting the stake on the outside to maximize the available volume for leaf expansion. We feel if the stake is not overly large, putting the stake on the inside is a great idea.

There are several other benefits. If the stake is on the inside:
1. A buck will not rub the stake with his antlers.
2. The bird can walk up and out on the stake
3. The tube is more wind stable and has a reduced profile in the wind.
4. Rodents cannot use the stake to climb up to the tie hole and gain entrance.

If you have any other ideas, please send them to me at and we will share them.

Again, If you need net we would be happy to supply it free of charge, but consider putting the stake on the inside.

Wednesday, June 24, 2009

Results: Plantra Weed Mats

I have been testing various hybrid oaks for cold hardiness in Minnesota. Yesterday I was out in the field planting some new trees to replace a few that succombed to the -30F temps we had last winter (that's just in SE Minnesota; another test site in NE MN reached -50F!). Most of the hybrids did very well despite coming from more southern seed sources... the ventilation of Plantra Tree Tubes really helps trees harden off for winter as compared to the old solid wall tubes (in which even native, local seed source trees had difficulty going dormant in time for that first hard frost - which can come as early as mid-September here in MN).

In order to replace the dead trees I had to first remove the Plantra Tree Tubes and Weed Mats. These tubes and mats were installed the first week of October 2008. The mats were applied over living, green grass, thistles, goldenrod, etc.

The photo above shows what I saw when I peeled the weed mats away from the planting spot (click photo to enlarge): Nothing!.. except bare soil, dead weeds, and one lonely sprig of grass that tried to take advantage of the small L-slit in the center of the mat and the advantageous growing environment in the tube.
Very cool.

Sunday, June 21, 2009

It's the Carbon Stupid!

Question: “Interesting, you make and sell tree tubes. So what does a Tree Tube do?”

That is a stressful question at a party. Spouses of those of us in the tree tube industry get a look of alarm when we are asked the simple and innocent question, “What does a tree tube do?” The reason is that a tree tube seemingly does many things and there is no obvious end to the monologue. Where do we begin? Here is a partial list:

A Tree tube:

1. Is used on tree seedlings, acorns, nuts, tissue culture plantlets, grafted grape vines, and etc.

2. Protects the plant from deer, rabbits and other animals

3. Shields from herbicide spray

4. Blocks the wind

5. Conserves moisture

6. Trains the plant to a single

7. Modifies the quality, quantity and wavelength composition of the light hitting the seedling

8. Has photomorphogenic effects

9. Is not a season extender

10. Affects CO2 uptake

11. Protects against mechanical damage

12. Makes it possible to find a plant in the forest to take care of it

13. Works best with small plants

14. Prevents side branching

15. Saves training labor

16. Is made of translucent polyolefin

17. Is tubular

18. Must be the equivalent of 3.5 inch OD in cross-section

19. Prevent seasonal buck rub

20. Discourages rodents

21. Ad infinitum…

I could go on indefinitely.

For over twenty years, my colleagues and I have searched for understanding of what it is a treeshelter or tree tube does to makes trees grow so magnificently. The answer is complex and involves a great deal of plant physiology. What is the simplest way to express what a tree tube does? Around 1pm on Friday afternoon (19 June 2009), it dawned on me. It is possible in three or four words to express the purpose and function of a tree tube. A tree tube does Carbon Acquisition and Retention (CARe) CARe is all a tree tube does. Plantra Tree Tubes CARe!

Everything about a tube flows from these concepts. So here is the answer I have been looking for – with some attempts at developing a useful acronym.

Answer: A tree tube is a Carbon Acquisition and Retention Device (CARD for short) Acronyms help us hold and retrieve knowledge. CARD is not a helpful acronym for what a tree tube does. A better acronym would spell a metaphor. Hmm… CARE or CARe meets that test. So my answer could be “A tree tube is for Carbon Acquisition and Retention (CARe).” Just thought of a third acronym - metaphor. The answer could also be, “The purpose of a tree tube is Acquisition and Retention of Carbon (ARC)” I know Noah’s ark has a “K” and not a “C”, but it is highly suggestive of the notion of saving a species. The Plantra Tree ARC has a ring to it!

The short story is that a Plantra Tree Tube does two things. First, it helps the plant acquire more carbon than it would without the tube and then the tube helps the plant retain the carbon by preventing browsing animals from removing carbon in the form of leaves, buds and twigs.


Since water is most often used as the electron donor in oxygenic photosynthesis, the equation for this process is:

CO2 + 2 H2O + photons(CH2O)n + H2O + O2

carbon dioxide + water + light energy → carbohydrate + oxygen + water

Every fan of science fiction has heard the expression that Earth based life forms – plants and animals – are carbon based. Life on Earth is fueled and made possible by Chlorophyll in leaves. Chlorophyll takes energy from sunlight to chemically convert water and carbon dioxide into sugar (carbohydrate), water and oxygen. Sugar is the fuel of life for both plants and animals. Animals consume plants to get sugar. Oxygen is consumed to “burn” the sugar fuel. When animals release the energy in the plant sugar, water and carbon dioxide are the byproducts. Therefore, animals produce the CO2 & H2O that plants consume to produce sugar and O2 that animals consume in a never-ending cycle. It is all about moving the carbon from plant to animal and back to the plant.

So exactly how does a grow tube help the leaf take in more CO2 than an unaided plant? The carbon used in photosynthesis must enter the leaf through open stoma or stomata. The stoma is a pore in the leaf that opens and closes with the action of two guard cells. The problem is that water vapor escapes out the stoma when open (so does O2, but that is not a problem). To conserve water the stoma only open when conditions are right for photosynthesis and it is not too dry or windy. If it is too dry or too windy, the loss of water is too great for the plant to remain turgid (not wilted) and the stoma close the guard cells. Closed stoma means no CO2 and no CO2 means no photosynthesis. The microenvironment in a tube is humid and still – no wind. There is little evaporative demand in the tube, so there is little loss of water when the stomas are open. Therefore, the stoma stays open continuously. (Bergez Dupraz 1997) There is no interruption in the supply of carbon (CO2) unless the plant depletes the CO2 in the tube. That will happen in an unvented tube on a sunny day that is otherwise ideal for photosynthesis. Without venting the CO2 level in the tube drop below a level that sustains photosynthesis and the plant goes into photorespiration and starts giving off CO2. Venting replenishes the CO2 supply available to the leaf.

It is only a slight exaggeration to say that life on earth is about move carbon into plants, then animals and back. Plantra Tree Tubes move carbon.


This is the easy part. Plantra Tree Tubes prevent browsing up to the height of the tree. The tube is a visual and physical barrier. The animals can’t see the plant. The animals can’t get to the plant.

Tuesday, June 16, 2009

A bluebird's story on life...

To view a comical story with pictures about a bluebird's experience in selecting a mate and choosing a nesting box click here: This narrative offers a truly different perspective, from our feathered friends, and will bring a smile to your face!

The pictures and narrative were actually put together by the tree farmer- Arlyn Perkey, who is working to grow and re-establish resistant American chestnuts in the US. One of the photos shows how the chestnut seeds are grown in milk cartons before being out planted and protected by tree tubes on his acreage.

Friday, June 12, 2009

Great Reading: American Chestnut

This isn't just great reading, it is must reading for any lover of trees and epic quests: American Chestnut: The Life, Death, and Rebirth of a Perfect Tree, by Susan Freinkel. It's available here, along with another amazing book published by the American Chestnut Foundation, Might Giants: An American Chestnut Anthology.

At Plantra we often say that our customers are our heroes. Beside the fact that Susan Freinkel's book is beautifully written, and beside the fact that it chronicles the greatest ecological catatrophe on this continent since the ice age, and beside the fact that it chronicles the heroic efforts of so many dedicated scientists and laymen to right this ecological wrong despite incalculable odds... beside all that the book has special meaning for us at Plantra because we have had the great good fortune to have met many of the heroes mentioned in the book, and to be playing at least a small role in helping them protect their young chestnut trees... hopefully making their work just a little bit easier.

We are proud to play a small role in the fight to restore the majestic American chestnut to its rightful place in the forests of its native range.

Thursday, June 11, 2009

Trail Cam: Searching Elsewhere For Dinner

This spring we set up 2 trail cams to show how Plantra Tree Tubes protect seedlings from deer and to provide a time lapse chronicle of the growth of this western Minnesota hedgerow planting. These trees were planted 4 & 5 years ago, but deer had kept them browsed to knee height until we tubed them this spring. In the first week we got this shot (click the photo to enlarge). She's hard to see but a doe is walking into the field behind the tubes... going elsewhere in search of food now that the seedlings are protected!
Stay tuned for more trail cam updates throughout the summer.

Wednesday, June 10, 2009

Seedling Compass

Blighted Trees

Tim Eck is a very active volunteer with the The American Chestnut Foundation - an organization every tree person should join. On a LISTSERV or mailing list for TACF, Tim asked the following question:
In another list site, the concept of solar polarity arose. Some horticulturists believe that you should mark the (compass) orientation of a tree before transplanting so the orientation can be retained upon transplantation.
While I find it difficult to believe that a one year seedling would be set back due to "disorientation", I might believe it for a more typical nursery size. People also pointed out that when they have a plot of distichous plants or bulbs, they noticeably orient with the compass points.
Any comments or experiences?
My answer to Tim follows:

Where I have run into the recommendation to retain the polar orientation when transplanting, it was to prevent frost cracking in thin barked species such as maple. As I recall, the theory is that the bark has somehow developed strength and/or elasticity to accommodate the expansion and contraction that occurs on the sides that are exposed to the sun. Whenever I have seen a frost crack dissected, the crack has always started at a wound site and propagated from there. Dr. Larry Severeid has some pictures illustrating this in black walnut.

Also I have only seen this recommendation for sapling sized trees and never for 1-0 or 2-0 seedlings. Bareroot seedlings are always planted randomly and I see no meaningful benefit from maintaining the orientation except one. A very important reason. The act of maintaining the orientation will require the grower to handle the plant very carefully. Handling plants carefully matters hugely. I remember visiting a planting where the grower claimed extraordinary growth by playing music on large speakers in the plantation. What I was a plantation with an exemplary degree of husbandry. The weed control was perfect. The fertilization was a secret (and very expensive) mixture frequently and carefully applied. Plants respond to care. Those who play music for their plants also notice when they need water. They see the bugs before it is too late.

Bottom line: Don’t worry about the orientation of a seedling, but the growers who do will have better trees – for the reasons above..

Wednesday, June 3, 2009

Great Reading: Farming For Wildlife

I recently came across a great article on planting hard mast (oaks, hickories, chestnuts, etc.) trees for wildlife, written by our friend Dudley Phelps for Mossy Oak's "Farming For Wildlife" magazine. Here's the link: Dudley has some great thoughts on taking topography & wind direction into account when deciding where to plant mast trees.

I love reading things that make me smack my (every increasing) forehead and say, "Why didn't I think of that?" Among several such points that Dudley makes in his piece is this gem: A few rows of mast trees can have benefits for influencing travel patterns of deer on your property long before the trees every begin producing acorns. That's because the tree row creates an edge, and deer always prefer to travel along edges. It reminded me of a remarkable thing a landowner once pointed out to me: He had a field where 2 different plots - one was a millet food plot and one was a prairie grass area - joined each other. The difference in height between the 2 types of vegetation was just a few inches (you had to look twice to even notice the difference when the plants were dormant). But sure enough the deer knew the difference and used that edge as a travel corridor from one stand of timber to another.

So when you're planting hard mast trees, soft mast trees, and shrubs keep in mind that your planting can pay dividends long before the planting begins bearing fruit & nuts... if you think in terms of creating structure, edges and travel corridors.

Tuesday, June 2, 2009

Results: The Tale Of Two Acorns

It was the best of times, it was the worst of times... And that's why you need Plantra Tree Tubes!

Longtime friend Arlyn Perkey (US Forest Service, retired) sent this great set of photos from his property in West Virginia. Here's the story: In spring 2007 he planted 2 red oak acorns in a Plantra Tree Tube. Both nuts germinated and grew. In the spring of 2009 he lifted the tree tube, and replaced it over just one of the seedlings, leaving the other unprotected.

Arlyn took this photograph on May 7, 2009:

As you can see, the seedling outside the tube has leafed out and looks good. The seedling in the tube has not quite started to leaf out, due to reduced light conditions (BTW the reduce light helps reduce stress & increase growth later in summer). For the seedling outside the tube, this was the best of times.

Now here's the photo Arlyn took on May 22, 2009 about 2 weeks later:

(click on the photos to enlarge them)
Thanks to the red bandanna that Arlyn added for background you can see that the situation has completely reversed: The seedling inside the tube has leafed out and is growing well. The seedling outside the tube was completely stripped of leaves by deer and is trying to leaf out again... no doubt only to be browsed by deer yet again. Outside the safety of the tree tube, it is the worst of times for this young oak!

(It's also a great photo of the dappled sunlight coming in through the vent apertures in the walls of the Plantra Tree Tubes!)

Thanks to Arlyn for a great set of photographs. After 20 years of trying I know how hard it is to get the right depth of field to take photos like this. To see more photos of Plantra Tree Tubes "in action," visit our photo gallery