Ventilated Plantra® O-Style Tree Tubes Ensure Planting Success Five Ways
Dappled Shade on Quercus agrifolia in a ventilated Plantra Tree Tube.
1. CO2 recharge: Plants grow using the energy in sunlight to combine water and carbon dioxide into carbohydrates and oxygen. In a conventional tree tube, photosynthesis proceeds at a rapid and uninterrupted pace that consumes the available CO2 and stops further growth. Good tree tube design allows for continual CO2 recharge. If not replaced, photosynthesis is not only slowed or stopped, but the plant is at higher risk for heat and moisture stress. On a calm day the ventilation in your Plantra Tree Tube allows for a gentle influx of air that maintains ambient levels of CO2 in addition to temperature and humidity. Vented tree tubes increased biomass by 50% over conventional shelters (Bergez & Dupraz 2000). Ventilation keeps your tree growing all day long.
2. Leaf fungus prevention: High humidity, free moisture and low light may combine to form conditions that promote fungal disease on leaves in tall conventional treeshelters (Mielke & Ostry 2004). While reducing growth, these fungal diseases do not generally cause mortality. Anything that causes stress can tip the balance when other stressors are affecting your tree. Our overarching design goal for the Plantra Tree Tube is to eliminate every single biotic and abiotic environmental stress we can identify. The Plantra Tree Tube ventilation system does three things to control leaf fungus.
A. Reduced Humidity: Conventional tree tubes maintain fungal promoting high humidity throughout the entire tube. Plantra ventilation reduces overall tube humidity to levels close to ambient while maintaining the layer of super saturated air on the underside on the leaf vital for CO2 uptake. Ambient air enters through the narrow vents and gently moves through the tube without stripping the humid air surrounding the stomata that is necessary for CO2 uptake. B. Reduced Free Moisture: The super saturated air in a conventional tree tube causes condensation to form. Water is continually dripping on the leaves. This free water is a fungal nursery. Ventilation substantially reduces fungal forming free water. C. Low Light: We designed the Plantra Tree Tube to reduce light levels by around 70% to reduce heat and light stress. Intense direct beam light stops or slows fungal growth. Lower light is a risk factor for fungal growth. Ventilation creates a dappled light effect of shade interspersed with intense sun. This moving pattern of intense light and shade acts to reduce the risk of fungus while not increasing overall heat and light stress.
3. Root Shoot Ratio: Intermittent gusts of wind cause the plant to allocate growth away from shoot elongation to stem caliper and root expansion. Plantra ventilation allows wind gusts to move the leaves and stem inside a tree tube. This is good. When establishing a wild tree it is necessary to get the shoot above the browse line and over the weed competition as soon as possible. Still we do not want to do that at the expense of root development. We have to out-compete weeds for sun, moisture and nutrients. The ideal growth pattern expands the root system and elongates the stem at the temporary expense of stem caliper. When the apical meristem emerges from the tube and the stem is flexed in the wind the plant will reallocate growth away from elongation to stem caliper and root expansion. Often growers report a slowing of growth, but the leaves are still producing a phenomenal amount of carbohydrate that is now deployed to caliper and roots. Ventilation allows air movement that helps to promote root development and stem caliper (Whitehead 1961).
4. Dappled Light & Shade: Plantra Tree Tubes are used to grow broadleaved tree species. Tree leaves of various species have evolved a wide range of light sensitivity or tolerance. Sun adapted leaves are often small with the photosynthetic structures (chlorophyll holding palisade cells) stacked on top of one another in layers because direct beam sunlight is able to penetrate deep into the leaf and drive photosynthesis. Small and compact leaves are a very efficient leaf structure for full sun. Shade adapted leaves are often large with a single layer of palisade cells. How do you design a tree tube that will drive photosynthesis in a sun tolerant plant without burning up the shade adapted plant? The Plantra Tree Tube is designed for efficient photosynthesis in both sun-loving and shade tolerant trees. Here is how we do it:
A. Block Bad Light: Yes, there is bad light. Light radiation does two things for a plant. Some wavelengths of light drive photosynthesis and many more wavelengths provide environmental information that plants have evolved to use to determine the ideal growth strategy for that set of environmental variables. Too much radiation of all types wastes water by warming the leaf and increasing evaporative demand (sweating). We block as much of the useless and unwanted light energy as possible while letting in as much good light as possible. For example, besides heating up the leaf, green light actually stunts growth (Folta & Maruhnich 2007) without contributing to photosynthesis. The good light in a Plantra Tree Tube is reddish because red light drives photosynthesis and through the phytochrome pigment system encourages root and stem development. The chart at right shows the various effects of light as known in 1980 (Light and Plant Life, Whatley and Whatley 1980).
B. Diffuse the Good Light: Diffuse light reduces solar stress and boosts photosynthesis by about 20% (Cavazzoni, et al, 2002). Your Plantra Tree Tube diffuses the photosynthetically active light radiation (PAR). Diffuse light hits the leaf randomly and stimulates all of the light catching photosynthetic structures no matter the orientation of the leaf or the structure. That means photosynthesis proceeds at a high rate without the heat stress of intense light levels. We chop, cook and grind food to make it easier to digest and absorb efficiently. Similarly, the Plantra Tree Tube diffuses, filters and selectively reflects light to allow a leaf to absorb and use light energy in an efficient and stress free manner.
That means photosynthesis proceeds at a high rate without the heat stress of intense light levels. We chop, cook and grind food to make it easier to digest and absorb efficiently. Similarly, the Plantra Tree Tube diffuses, filters and selectively reflects light to allow a leaf to absorb and use light energy in an efficient and stress free manner.
C. Dappled Shade/Light: This is new and important. Dappled shade creates moving patches of high and low intensity light. The bright patches are able to meet the minimum threshold for photosynthesis in sun adapted leaves while not over heating shade adapted leaves. Dappled light allows the sun adapted leaf to thrive without stressing the shade adapted leaf.
5. Dormancy: Treeshelters were invented in the United Kingdom by Graham Tuley. We all owe him a tremendous debt of gratitude. And 100s of millions of oaks owe Graham their lives. The UK environment where treeshelters were invented by Mr. Tuley could be characterized without exaggeration as EXTREME moderate. Since the UK is north of all US states except Alaska, it never gets hot. Oddly, it never gets cold either. The ocean influence is so strong you can grow palm trees in Ireland. Dublin at 53ºN latitude is 4º closer to the Arctic Circle than Winnipeg, Canada (49ºN). Stop and think about that for a second. The USDA developed Hardiness Zone Maps to guide North American growers to select plants and trees that will tolerate the minimum expected cold temperatures in a given location. The UK developed hardiness maps based on the US standard. (Why they bothered, I have no idea) If you go to the link and select the option to match the “US colour” scheme, you will discover that the British Isles are dominated by the same brown color keyed hardiness zone found in the Florida Panhandle. In 20 years of work with treeshelters in North America we have never had a winter dieback complaint from anywhere near Florida. We needed to adapt tree shelter technology to US conditions where folks want to grow northern hardwoods. Ventilation is the answer. Young plants are especially susceptible to dieback due to a tendency toward indeterminate growth (Bigras 1996 pg 173). Heat and moisture promote plant activity and retard dormancy. Ventilation cools the plant with ambient air temperatures on sunny days in the fall and reduces available moisture. Ventilated tree tubes promote normal dormancy.
