Tree Tube Research, Field Trials & Independent Studies
Tree Tube & Tree Shelter Research, Field Trials & Independent Studies
Tree tubes and tree shelters are not all the same. Choices in light diffusion, venting, tube height, stake material and overall system strength directly affect survival, growth and long-term success. A well-designed tree tube system — combining a vented shelter with a flexible fiberglass stake — performs very differently from a tube installed on a weak or rotting stake. This page summarizes independent research and real-world field trials where Plantra products – especially SunFlex® Grow Tubes and Jump Start® Grow Tubes for Vines – were used in the methods or reported in the results.
Our goal is simple: summarize what the studies actually show, explain how we interpret the results in practical plantings, and help you make decisions that align with the evidence on your site.
Plantra is a family-owned company founded by Joseph Lais. We are dedicated to designing and building SunFlex® Grow Tubes, Trunk Builder® Fiberglass Tree Stakes and Jump Start® Grow Tubes to match what the independent research shows in the field.
On this page
| Study / Institution | Species & Focus | Key Finding / Result |
|---|---|---|
| 1. University of Minnesota | Bur Oak | SunFlex® Grow Tubes outperformed Tubex. Seedlings had 2x the stem diameter and better height growth in Plantra tree tubes. |
| 2. Wisconsin DNR | Oak, Walnut, Cherry | System integrity is critical. Stakes were the weak link; flexible fiberglass tree stakes are essential to prevent complete failure. |
| 3. TACF & USFS | American Chestnut | 92% survival with Plantra shelters. Seedlings protected by 5 ft Plantra tree tubes nearly doubled survival compared to direct seeding (49%). |
| 4. Purdue HTIRC | Hardwoods | Diffuse light builds strength. Higher light transmission (SunFlex style) creates better root-to-shoot balance in tree protectors. |
| 5. USDA PNW | Oregon White Oak | Avoid dark, unvented "oven" tubes. Dark, unvented tree tubes caused heat stress and lower growth compared to light-optimized, vented tree tubes. |
| 6. Stroud Water Research | Riparian Buffers | Durability matters. In mass plantings, reusable Trunk Builder® fiberglass tree stakes and durable tubes reduce long-term costs. |
| 7. SARE (Grazing) | Silvopasture | Cattle-resistant systems. Switching to SunFlex® Grow Tubes & Trunk Builder® Fiberglass Tree Stakes stopped wind and livestock damage seen with wood stakes. |
| 8. Univ. of Missouri | Grapevines | Safe establishment. Jump Start® tubes accelerated early growth and prevented herbicide damage with no yield penalty. |
Independent Studies & Field Trials
These summaries are based on publicly available reports and journal articles. The trials were designed and run by agencies, universities and research organizations. Plantra products were one of the tools they used; we did not design or control these experiments.
1. University of Minnesota – Trout Brook Bur Oak Trial
Institution: University of Minnesota
Location: Saint Paul, Minnesota, USA
Design: 5-year bur oak tree tube comparison
Study overview
This trial followed bur oak seedlings over five years using three treatments: SunFlex® Grow Tubes, Tubex Combi shelters, and unsheltered controls. The goal was to compare growth and survival across the systems under real-world conditions.
Key results
- Seedlings in SunFlex® Grow Tubes reached significantly greater height than those in Tubex Combi or control plots.
- Stem diameter inside SunFlex® was roughly double that of seedlings in Tubex Combi.
- Mortality was lower with SunFlex® (around 13%) versus Tubex (around 25%) over the trial period.
What this means for growers
For bur oak – a species that can be slow to get established – this trial showed a clear advantage in both growth and survival when using SunFlex® Grow Tubes versus the comparison shelter. In practical terms, that means more trees getting above browse height faster with fewer losses.
Shop 5 ft SunFlex® Grow Tubes with Trunk Builder® Stakes - Doe Shield System
2. Wisconsin DNR (2020–2025): Vented vs. Unvented Tubes in Regeneration Plantings
Institution: Wisconsin Department of Natural Resources – Reforestation Program
Location: Wisconsin, USA
Study overview
Wisconsin DNR is running a multi-year trial to compare vented and unvented tree shelters and unsheltered controls in operational reforestation. The trial follows seedlings of red oak, white oak and black cherry protected by SunFlex® Grow Tubes (vented) and Blue-X tubes (unvented), plus open controls.
Key findings so far
- Oak survival has been mixed, heavily affected by drought and deer interference.
- Black walnut has shown strong survival under both tree shelter systems.
- The most common failure mode is not the tube itself but stake failure and tubes being pulled off by deer.
- Reports emphasize that shelter performance collapses when the support stake is weak, underscoring the value of flexible, non-rotting fiberglass tree stakes.
What this means for growers
The Wisconsin data reinforces a simple point: the system is what works or fails. A tree tube system with a vented grow tube that stays upright and a flexible fiberglass tree stake performs very differently than the same tube on a weak, broken or rotted wood or bamboo stake. In higher buck-pressure sites, our 6 ft SunFlex® Buck Shield with Trunk Builder® Fiberglass Tree Stakes provides the height and stake strength the data supports. SunFlex® paired with Trunk Builder® Fiberglass Tree Stakes is designed to hold up for the full establishment window. Additionally, our stakes have a small profile and should be installed on the inside of the tree shelter, which keeps the stake away from curious deer and reduces leverage when they bump or rub the tube.
3. TACF & USFS – Allegheny NF American Chestnut Restoration (Pinchot et al. 2020)
Organizations: The American Chestnut Foundation (TACF) & USDA Forest Service
Location: Allegheny National Forest, Pennsylvania, USA
Study overview
TACF and the Northern Research Station installed large-scale plantings of hybrid American chestnut in shelterwood harvests on the Allegheny National Forest. They compared:
- High-quality chestnut seedlings planted in the field, each protected by a 5 ft Plantra tree shelter, and
- Direct-seeded chestnuts without comparable protection.
Key results
- Two years after planting, roughly 92% of seedling-planted chestnuts in Plantra shelters were alive.
- Only about 49% of direct-seeded, unprotected chestnuts were alive over the same period.
- Survival was consistently high across treatments when seedlings were planted and protected by shelters.
What this means for growers
For high-value or slow-replacement species like chestnut, nearly doubling survival is the difference between a successful planting and a failed project. This study supports using SunFlex-style reforestation tubes and tree tube systems as standard equipment wherever deer and competing vegetation are serious threats.
4. Purdue University (HTIRC) – Tube Light Levels, Stem Strength & Architecture
Institution: Hardwood Tree Improvement & Regeneration Center (Purdue University)
Focus: Effects of tree shelter light transmissivity on root/shoot balance
Study overview
Purdue-affiliated researchers evaluated how different shelter wall transmissivities (from very dark to relatively clear) affect morphology and biomass allocation of oak and pine seedlings. They wanted to know whether dark, low-light tubes create tall, weak “noodle trees,” while lighter tubes promote sturdier trunks and healthier root systems.
Key results
- Seedlings grown in darker tree protectors with very low light transmissivity had less above- and below-ground growth and a higher leaf-to-root mass ratio.
- As shelter transmissivity increased into a moderate range, both shoot and root growth improved and plants allocated biomass more evenly.
- The work reinforces that grow tubes admitting more diffuse light help build stronger stems and better-developed roots, reducing the “spindly tree” problem.
What this means for growers
This is the physiology behind what you see in the field. Light-diffusing tree tubes like SunFlex® keep trees growing, but also give them enough light to build wood, not just height. In windy or snowy climates, this is exactly what you want when the tube comes off: a tree that can stand on its own.
5. USDA Forest Service – Oregon White Oak Microclimate Study (PNW-RP-576)
Institution: USDA Forest Service, Pacific Northwest Research Station
Location: Southwestern Washington, USA
Study overview
This study tested four shelter types – fine-mesh fabric, white solid tubes (vented and unvented), blue solid unvented tubes, and an unsheltered control – around Oregon white oak and western redcedar. Researchers measured air and leaf temperature, humidity, photosynthetically active radiation (PAR), and seedling growth inside and outside the tree tubes.
Key results
- Solid tubes raised daytime temperatures relative to ambient conditions; the blue unvented tube produced the darkest, hottest interior with the lowest light levels.
- All shelter types increased height and diameter growth of western redcedar compared with unsheltered seedlings.
- For Oregon white oak, photosynthesis and diameter growth in the blue unvented tubes were significantly lower than in unsheltered seedlings, showing that too little light can hurt stem strength even when height looks good.
What this means for growers
Tube color, venting and light transmission directly shape the microclimate around seedlings. Very dark, unvented designs can create low-light, high-heat conditions that stunt diameter growth and carbon gain, especially in light-demanding species. Vented, translucent tree tubes with good light diffusion – like SunFlex® – strike a better balance between protection and productive microclimate.
6. Stroud Water Research Center – Riparian Shelter Comparisons
Institution: Stroud Water Research Center & partners
Context: Forested riparian buffer establishment
Study overview
Stroud compared three brands of 5 ft shelters in riparian forest buffers: vented Plantra shelters (SunFlex-style), Tubex models and nonvented Suregreen tubes. They tracked survival, height, stem failure and practical issues like stake durability and tube reuse across multiple planting seasons.
Key findings
- The study found few statistically significant differences in seedling survival or height growth among brands when systems were installed and maintained correctly.
- Where failures did occur, they were usually related to broken or poorly installed stakes and maintenance gaps, not tube brand.
- Using any quality tree shelter substantially improved establishment odds compared with no shelter at all.
- Stroud emphasized program logistics, tube durability and waste management (including reuse) as major considerations in large riparian projects.
What this means for growers
Stroud’s work shows that real-world performance hinges on system design and installation quality as much as brand choice. In riparian buffers where thousands of trees may be planted at once, choosing a durable shelter with a reusable fiberglass tree stake – and budgeting for maintenance – matters more than differences between competing high-quality tubes.
7. SARE Lickskillet Farm – Tubes in Grazed Systems
Program: USDA SARE – Sustainable Agriculture Research & Education
Project: FS22-342 – Lickskillet Farm
Study overview
This on-farm project looked at tree establishment in grazing systems. Researchers initially installed 5ft TreePro shelters with bamboo stakes. Those shelters were heavily damaged by wind and livestock, forcing a change in approach. They then switched to SunFlex® Grow Tubes with Trunk Builder® Fiberglass Tree Stakes.
Key results
- TreePro Slit shelters with weaker bamboo stakes suffered significant wind damage and were dismantled or scattered by cattle.
- After switching to SunFlex® Grow Tubes and Trunk Builder® Fiberglass Tree Stakes, the new tree shelter systems resisted wind and animal pressure much better.
- Growers reported improved survival and less maintenance once the SunFlex® systems were in place.
What this means for growers
In any grazed environment – silvopasture, alley cropping, pastures with scattered shade trees – the weak link is usually the stake and attachment system. If the stake fails, the tube fails, and if both hold, trees have a real chance. The SARE project echoes what we see in many silvopasture and agroforestry installations. Remember to always install the Trunk Builder® Fiberglass Tree Stake on the inside of the SunFlex® Grow Tube.
8. University of Missouri – Jump Start® Grow Tubes for Vines
Institution: University of Missouri
Crop: Grapevines
Important product distinction
This is a vineyard study using 30" Jump Start® Grow Tubes for Vines, not SunFlex® Grow Tubes for trees. These shorter vine tubes are designed for grapes and similar crops, not for forestry or tree shelter applications.
Study overview
Under Dr. Andrew Thomas, the trial compared four treatments:
- Plantra Jump Start® 30" vine tubes
- Short waxed cartons
- No tube
- “Fan” training without any tube
Key results
- Inside the tubes, vines grew longer but initially had thinner shoots due to altered light conditions.
- Above the tube height, differences in growth largely disappeared as vines developed.
- Vines in tubes had essentially zero herbicide injury, while around half of unprotected vines were damaged by glyphosate drift.
- By years 3–4 there was no meaningful difference in yield, vigor or survival among the treatments.
What this means for growers
The Missouri study shows that Jump Start® Grow Tubes for Vines change the early growth pattern but do not penalize vineyard performance once vines are established. The accelerated early growth saves time by allowing growers to train the vine to the wire system earlier. The Jump Start® vine grow tubes protected against herbicide injury and browse during the vulnerable establishment phase without costing yield later.
Background Science: Light, Venting & System Design
Diffuse light and photosynthetic efficiency
Modern research in greenhouses and tree tubes has shown that diffuse light – sunlight scattered to reach leaves from multiple angles – improves whole-plant photosynthesis compared to harsh direct light alone. SunFlex® Grow Tubes utilize a twin-wall profile and specific pigments to diffuse sunlight. This "greenhouse effect" stimulates the plant's phytochrome pigments, encouraging the tree to build a functional canopy with improved root-to-shoot balance rather than just stretching for height.
Cross-Flow™ venting and CO2 recharge
A tree protector must modify temperature without suffocating the tree. Unvented tubes can limit CO2 availability, creating a bottleneck for growth known as the "oven effect." Vented designs like SunFlex® feature Cross-Flow™ venting technology. This allows hot air to escape and, crucially, replenishes the CO2 that the tree consumes during photosynthesis. This airflow also limits prolonged leaf wetness that favors fungal disease while maintaining a "Shock Prevention Zone" that shields young leaves from drying winds.
Thigmomorphogenesis: Why flexibility matters
Several of the studies above (Wisconsin DNR, SARE) conclude that "tube failures" are often actually stake failures. But the stake does more than hold the tube up; the stake influences stem strength and caliper. Thigmomorphogenesis is the botanical term for how trees respond to wind. Movement triggers the production of strengthening tissues in the stem. Rigid stakes (wood, bamboo, rebar) prevent this movement, leading to weaker trunks. We pair SunFlex® with Trunk Builder® Fiberglass Tree Stakes specifically because their "flex" allows the tree to sway naturally in the wind, building the caliper and root strength necessary for long-term survival after the tube is removed.
How SunFlex® Works: The Science Behind the Results
The independent studies above show a consistent pattern: vented, light-diffusing shelters paired with flexible, non-rotting stakes outperform dark or unvented tubes installed on rigid or weak stakes. The SunFlex® system was engineered around these exact principles. Here is the underlying plant physiology and microclimate physics that explain why SunFlex® performs the way it does.
1. Diffuse Light Increases Photosynthesis & Stem Strength
SunFlex® uses a twin-wall profile and pigments that scatter incoming light. Diffuse light penetrates deeper into the canopy, allowing more leaves to photosynthesize. Research from Purdue (HTIRC) and USDA PNW shows that darker, unvented tubes limit interior light and produce tall, weak stems (“noodle trees”), while diffuse-light shelters build stronger wood and better root architecture. This matches the superior height and caliper results seen in the Minnesota bur oak trial.
2. Cross-Flow™ Venting Prevents Heat Spikes and CO2 Depletion
Inside unvented tubes, seedlings quickly consume available CO2, reducing photosynthesis, while heat accumulates to stressful levels. SunFlex® Cross-Flow™ venting allows fresh air to enter while warm air escapes, improving carbon exchange and stabilizing interior temperature. USDA PNW-576 found that vented shelters maintain healthier leaf temperature and better photosynthetic function compared with dark, unvented designs.
3. Greenhouse-Style Microclimate Accelerates Establishment
The combination of moderated temperature, reduced wind stress, and elevated humidity creates a stable greenhouse-style microclimate. Trials from Minnesota, Wisconsin and TACF document faster early growth and higher survival when seedlings are protected from stem desiccation, herbicide drift, and mechanical damage. This is why species like oak, chestnut and riparian hardwoods consistently show better establishment under SunFlex® systems.
4. Flexible Trunk Builder® Fiberglass Stakes Build Wood, Not Whip
Rigid or rotting stakes cause tubes to lean, collapse, or detach. Flexible fiberglass stakes transfer wind energy to the stem in controlled pulses—thigmomorphogenesis—strengthening the trunk instead of producing a weak, tall whip. This is why stake failure is the #1 cause of tube failure in the Wisconsin DNR and SARE studies, and why Trunk Builder® stakes repeatedly outperform wood and bamboo in real installations.
5. Height Matters: Match Tube Height to Deer Behavior
Deer browse between roughly 30–60 inches, while buck antler rubbing commonly destroys stems up to about 72 inches. SunFlex® 5 ft systems get trees above typical browse height faster in moderate-pressure areas; the 6 ft Buck Shield™ system extends protection into the antler rub zone that state agencies and foresters regularly cite as a major cause of seedling mortality. The illustration below shows approximate height zones in a typical deer stand and why 5 ft and 6 ft systems matter.
Match SunFlex® Grow Tube Height to Animal Threat
Use this guide to choose the minimum SunFlex® Grow Tube height based on the animals on your site. Taller tubes can always be used when in doubt.
Grow Tube*
(mice, voles, rabbits)
Large Hares
Nutria
heavy deer areas
moderate deer areas
girdling
large hares
(mice, voles, bunnies)
Shaded cells indicate the minimum recommended grow tube height for protection from that animal
threat.
*If planting on hillsides, taller tube height may be necessary to protect seedlings on the up-slope side.
When you combine a vented, diffuse-light shelter with a durable, flexible fiberglass stake—and match the system height to the site’s animal threat and pressure—you get exactly what the research shows: faster establishment, stronger stems, and significantly higher survival.
How to Use This Research in Your Planting
- Use tree tubes where browse, mechanical damage or harsh microclimates threaten establishment. Chestnut, oak, riparian hardwoods, urban trees and tropical crops in exposed sites all show better survival and growth with protection.
- Match height to browse pressure. In heavy deer and buck country, lean toward 6 ft systems. In moderate deer zones, 5 ft tree shelters often align with the trials summarized above.
- Treat the stake as a critical component, not an accessory. For grazed systems or sites with strong wind, always choose Trunk Builder® Fiberglass Tree Stakes that fit your budget and project length.
- Keep weed competition under control. Tree protectors protect the stem and leaves; they do not eliminate the need for weed management around the root zone.
- Use the right product line for the crop. SunFlex® Grow Tubes are for trees and shrubs. Jump Start® Grow Tubes for Vines are for grapes and similar vines; the Missouri study confirms they do the job without sacrificing yield once vines are established.
Frequently Asked Questions
Are these studies independent from Plantra?
Yes. The studies summarized here were conducted and published by universities, public agencies and research organizations. Plantra tree tubes were one of the tools they evaluated; we did not design or run the experiments.
Do SunFlex® Grow Tubes always outperform other shelters?
No single shelter wins every trial. In some studies, SunFlex® Grow Tubes show higher survival or faster growth. In others, performance is similar to other quality tree protectors. The consistent pattern is that vented, greenhouse-style tubes paired with flexible fiberglass tree stakes perform best as a system across species and sites.
Are Jump Start® Grow Tubes for Vines the same as SunFlex® Grow Tubes?
No. Jump Start® Grow Tubes for Vines are shorter, C-style protectors used primarily in vineyards. SunFlex® Grow Tubes are taller, O-Style tree shelters designed for forestry, conservation, habitat restoration, and protecting trees from deer.
Can I use this research to justify funding or grant applications?
In many cases, yes. Agencies and funders often want to see that you are using proven establishment methods. Citing these independent studies in your project narrative can help show that your approach is grounded in real-world data, not guesswork.
References
- University of Minnesota. Trout Brook Bur Oak Trial. Green Report 2018–2019, p. 44 – comparison of SunFlex® Grow Tubes, Tubex Combi shelters and unsheltered controls.
- Wisconsin Department of Natural Resources. Reforestation Annual Reports (2020–2025). Vented SunFlex® Grow Tubes vs Blue-X vs unsheltered controls in oak and cherry regeneration.
- Pinchot, C.L., et al. 2020. “Using oak silviculture to reintroduce American chestnut.” USDA Forest Service Northern Research Station – Allegheny National Forest study using 5 ft Plantra shelters on chestnut seedlings.
- Vázquez de Castro, A., et al. 2014. “Light transmissivity of tube shelters affects root growth and biomass allocation of Quercus ilex L. and Pinus halepensis Mill.” Annals of Forest Science – work on shelter transmissivity and plant architecture.
- Devine, W.D., Harrington, C.A. 2008. “Influence of four tree shelter types on microclimate and seedling performance of Oregon white oak and western redcedar.” Research Paper PNW-RP-576. USDA Forest Service, Pacific Northwest Research Station.
- Stroud Water Research Center. “Research on methods for forested buffer restoration – stone mulch and tree tubes” – riparian buffer study comparing Plantra (SunFlex), Tubex and Suregreen shelters.
- USDA SARE. Project FS22-342 – Lickskillet Farm. On-farm experience replacing damaged TreePro shelters with SunFlex® Grow Tubes in grazed systems.
- Thomas, A., et al. 2017. University of Missouri. HortTechnology 27(2): 248–259 – four-year vineyard trial using Jump Start® Grow Tubes for Vines, waxed cartons and no-tube controls.
