Treeshelters & Winter Die Back: That Was Then, This Is Now

This 1997 research study appears prominently in web searches for treeshelters. The conclusions reached by Doug Lantagne and Raymond Miller at that time and on that study site were that solid wall treeshelters did not increase height growth and were not successful in helping to regenerate red oak. Naturally, we are often asked about this study and others like it.

Our answer often surprises the questioner: They were right. And then we elaborate: They were right then, but they wouldn't be right today due to the dramatic changes and improvements in treeshelter (tree tube) design.

The Lantagne/Miller paper was the result of six years of testing, meaning that the seedlings were planted and treeshelters were applied either in 1990 or 1991. Keep in mind that the first treeshelters were imported to the USA from the UK only in 1988, and were commercially available only in 1989. These were early days.

The researchers - and everyone using treeshelters back then - were using a product that,
1) Clearly had fantastic potential to solve several problems limiting the success of hardwood regeneration, especially deer browse, weed control (by shielding seedlings from herbicide spray, not to mention clearly marking seedling location amidst the brush), and moisture/drought stress
2) In retrospect were perfectly suited to the moderate, maritime climate of the United Kingdom, but were ill suited in several important respects for the climatic extremes of North America. The moderate climate of the UK was very forgiving on treeshelter design characteristics that our more extreme climate later exposed as design flaws.

The two most important design changes during that period of time have been: Recognizing the importance of tube diameter in promoting thicker stems and balanced root/shoot ratio, and the revolutionary introduction of ventilation. Both topics are covered in more detail here and here.

In the early days of treeshelter use in the USA reports of initial growth acceleration followed by a period of slow growth that allowed un-tubed trees to catch up were common. Why was this? Ironically, it was not until treeshelters were adapted on a large scale for use in commercial vineyards (and were re-dubbed "grow tubes") that we had to controlled & uniform growing conditions necessary to learn the answer: Diameter. In small diameter tubes (and those early treeshelters came in nested groups where the diameter of the inside tubes was too small) the leaves shade each other and the stem to a much larger degree. This in turn triggers a "shade avoidance" growth response in the tree - it shoots upward for light, but invests little growth energy in thickening its stem or developing roots. Upon emergence from the tube and exposure to full sun and wind, the tree then slows or even halts height growth while it reallocates growth energy into stem thickness and root growth... thus allowing un-tubed trees to catch up (provided they hadn't been eaten by deer!).

Plantra Tree Tubes have a much larger diameter - 3.9 inches - than the average diameter of those early treeshelters. The result: Much more balanced growth while inside the tube, so there's no need for the "rebalancing" period upon emerging from the tubes. Growth builds on growth, and there's no chance for un-tubed trees to catch up.

The Michigan State researchers mention winter die back as the main reason un-tubed trees caught up to or surpassed those in solid wall treeshelters, and they were right. This was a real problem throughout the 1990's with solid wall treeshelters. After a summer of rapid growth hardwood seedlings in those early solid wall treeshelters would simply keep right on growing deep into the autumn; they did not get the moisture (drying) and temperature signals they need to initiate dormancy. They were the forestry equivalent of hothouse orchids. Consequently when the first killing frosts of autumn came these trees often suffered significant die back from the tip down. It was better than getting eaten by deer, and eventually the trees would re-sprout and emerge from the tubes early enough in the growing season to properly harden off for winter, but it was far from ideal.

The introduction of the vented treeshelter has solved this. Ventilation has several benefits - increased stem thickness, increased rate of CO2 exchange for optimal growth - but the most immediate and dramatic was the virtual elimination of winter die back of hardwood seedlings in treeshelters. Ventilation equalizes temperatures in & out of the tubes. And while the seedling still enjoys the moisture-stress reducing benefits of wind protection, vented tubes don't create the hothouse climate that leaves seedlings exposed to frost damage.

Since we introduced our Plantra Vented Tree Tubes we have not received a single phone call or email regarding winter die back. It is simply a thing of the past.

Researchers like Lantagne and Miller perform an extremely important role, testing new ideas and casting a spotlight on their shortcomings. This was a very important piece of research, one report among many that caused and encourage those of us who have been involved with treeshelters since the beginning to question long-held assumptions about treeshelter design and performance and try new ideas like ventilation that were once considered to be heresy among treeshelter makers.

The result: A Plantra Tree Tube design that is ideally suited to both hot and cold temperature extremes of North America... with more advancements on the way.

Lantagne and Miller were right about tree tubes at that time, but that was then and this is now!