How SunFlex® Works For Your Seedlings
The SunFlex® System combines greenhouse-grade grow tube technology with Trunk Builder® support stakes in a one-of-a-kind
seedling establishment system that works the first time, every time. SunFlex® protects seedlings from the moment you plant,
drives rapid and sustained growth, and builds a solid foundation for long-term success in the field.
What sets SunFlex® apart is that every part of the system is engineered on purpose, for a purpose—from the greenhouse film
and Cross-Flow™ venting to the Stem Guides™ (patent pending) and Trunk Builder® stakes that flex in the wind.
Click to view the full-size SunFlex® Grow Tubes with Stem Guides™ infographic (PDF).
SunFlex® Grow Tube
Greenhouse microclimate for faster, safer top growth
- Stem Guides™ (patent pending) protect the emerging stem and help discourage birds from perching on the tube.
- Growth-maximizing 4" inside diameter keeps leaves in the "sweet spot" for photosynthesis and uniform growth.
- Proprietary greenhouse film filters and diffuses sunlight to drive growth while helping avoid heat stress.
- Cross-Flow™ venting refreshes CO2 inside the tube and helps seedlings harden off properly for dormancy.
- Nurture Zone at the base reduces moisture loss from drying winds and shields seedlings from weed-spray drift.
Trunk Builder® Stakes
Flexible backbone that builds stronger trunks and roots
- Fiberglass stake flexes in the wind to trigger natural stem-thickening responses (thigmomorphogenesis).
- Virtually unbreakable and rot-proof, designed to last in the field long after wood or bamboo fails.
- Narrow profile and rounded "trunk-safe" top sit inside the tube, away from climbing rodents.
- Exclusive ground line marker makes correct install depth quick and repeatable for planting crews.
Together, SunFlex® Grow Tubes with Stem Guides™ and Trunk Builder® stakes form a complete seedling-establishment
system—protecting young trees while they grow straight, fast, and field-ready.
It All Starts With the Sun
The SunFlex® name says it all—like a greenhouse, it all starts with the sun. SunFlex® is built around what seedlings
actually need to photosynthesize efficiently: the right balance of sunlight, CO2, and water in a controlled
microclimate.
Ordinary “tree tubes” simply trap heat and block wind. SunFlex® uses twin-wall construction and a proprietary
pigment system to filter and diffuse sunlight. Diffuse light blankets leaves from many angles, which can increase
photosynthesis compared to harsh, direct beam light. At the same time, the film helps prevent temperatures from
becoming too hot inside the tube so seedlings can keep growing instead of shutting down from heat stress.
Cross-Flow™ Venting: CO2 Recharge and Proper Dormancy
Many older-style tubes are unvented or poorly vented. Once the plant uses the CO2 inside the tube, photosynthesis
slows to a crawl. SunFlex® solves this with Cross-Flow™ venting—carefully placed vents that allow fresh CO2 to
enter and circulate through the tube while helping manage humidity and temperature.
In the fall, Cross-Flow™ venting also allows cold air to move through the tube to help seedlings enter proper
dormancy. Unvented tubes can trap warmth well into autumn, which can delay dormancy and lead to winter die-back.
SunFlex® is engineered to grow seedlings hard and fast, then let them shut down on schedule so they come back
strong in spring.
Shock Prevention Zone: Protecting New Seedlings at the Base
At ground level, young seedlings are extremely vulnerable to drying winds and herbicide drift. The SunFlex® Shock
Prevention Zone shields the lower stem and roots from 100% of direct wind inside the tube and reduces
water loss from the soil surface. This helps prevent the “planting shock” that kills many seedlings before they
ever get established.
By stabilizing temperature and moisture around the root collar and protecting against weed-control sprays, SunFlex®
gives seedlings a much better chance to survive the transition from nursery to field.
Acclimation Zone: Training Leaves for the Outside World
As seedlings grow up through the tube, they enter the Acclimation Zone near the top. Here they receive a mix of
diffused light, dappled shade, and controlled air movement. This combination thickens leaves and stems and prepares
them for full exposure outside the tube.
Instead of going from a sheltered environment straight into harsh, open conditions, SunFlex® seedlings are
gradually hardened off. This reduces sunscald, windburn, and transplant shock when the tree eventually grows above
the tube.
Transition Zone: Guiding the Stem and Supporting the Trunk
The Transition Zone at the upper section of the tube does two key jobs. First, it uses color pigments in the tube
walls and blue light entering from the open top to encourage the tree’s natural phototropism—growth that channels
the main stem straight up and out of the tube while suppressing heavy lateral branches down inside the tube.
Second, this zone works with the Trunk Builder® stake to provide safe, centered support so the sapling grows into a
straight, strong trunk instead of a weak, leaning stem. The result is a tree that’s ready to stand on its own much
sooner than with traditional tubes and rigid stakes.
Why Trunk Builder® Stakes Are the Backbone of the System
Your grow tube installation is only as good as the stake behind it. That’s why Trunk Builder® stakes were
engineered from the ground up for this job—not borrowed from another industry. The 3-sided delta fiberglass
profile delivers a high strength-to-weight ratio with rapid “flex memory”: the stake bends with the wind, then
snaps back straight when the wind stops.
Rule #1 – Stake Flexibility + Memory = Stronger Stems and Trunks
Plant biologists have long known that stem movement from wind or mechanical contact triggers
thigmomorphogenesis—growth responses that lead to stockier, stronger stems. To get that natural strength, you
need a support stake that moves with the tree rather than acting like a rigid crutch. Trunk Builder® flexes in
any direction above ground and returns to straight, encouraging the tree to develop a thicker, more wind-firm
trunk and stronger roots.
Rule #2 – Rigid Wood and Bamboo Stakes Don’t Flex and Don’t Last
Wood and bamboo are common because they’re cheap—not because they’re good for tree growth. They are rigid, which
limits stem movement and can scallop holes in soft soil as they rock back and forth. In the real world they also
rot, crack, and snap off at ground level—often within the first couple of seasons. Considering grow tubes often
need to stay in place for several years, wood and bamboo simply can’t keep up.
Rule #3 – Engineered on Purpose, for a Purpose
Trunk Builder® stakes are purpose-built to support grow tubes and train tree trunks. Unlike rebar, T-posts,
electrical conduit, hollow plastic pipe, or improvised materials, Trunk Builder® is designed to flex, recover, and
keep performing season after season. It won’t rot, and it’s tough enough to stand up to wind, snow load, and even
buck rub in many installations.
Rule #4 – Ease of Use Matters
Whether you’re planting five trees or five thousand, installation speed and consistency matter. Trunk Builder®
stakes are matched to SunFlex® Grow Tube heights and include a built-in ground-line marker so crews know exactly
how deep to drive them—no guessing. With the matching stake driver, the slim profile slices into tough ground
where wood and hollow plastic stakes can stall or shatter, saving time and labor across large projects.
Putting the System to Work
SunFlex® is more than a tube with a stake—it’s a complete greenhouse grow tube system with a trunk-building
backbone. Put SunFlex® Grow Tubes with Stem Guides™ and Trunk Builder® stakes to work in your next planting and
give your seedlings the same advantage the pros rely on: faster establishment, stronger stems, and higher survival
in the field.
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