Table of Contents
What Is Blind Wood
Blind wood, also known as bare wood, is simply sections of apple wood where buds fail to grow, leaving bare, unproductive stretches of a limb or leader (Figure 1). Blind wood is a multi-year issue, leaving unproductive canopy windows that decreases orchard production, efficiency and ultimately profit. It originates on 1-year-old wood, but it doesn’t stay a “1-year-old wood problem.” That blind section persists as the wood ages. What you’re seeing in year 3 or 4 is just missed opportunity from year 1 (Figure 2).
These buds aren’t usually dead, they’re alive but suppressed. Physiologists call them paradormant buds, meaning they are present, but hormonally restrained from growing.
Paradormancy is a term used as the initial stage of dormancy in the tree occurring in the fall in preparation of winter. Para, a Greek word meaning “beside”, with dormancy, originating from the Latin word dormire meaning “to sleep”.
The term paradormancy fits well as the inhibition of a bud to break is not actually within the bud itself, but a mechanism or mechanisms in part of the plant, beside the bud.
Orchards with unmanaged blind wood have:
- Less effective bearing surface
- Uneven light distribution
- More variable yields from year to year
Certain cultivars are more prone than others to have blind wood, especially those with high vigour and high apical dominance, such as Ambrosia, Fuji, Honeycrisp and Jonagold.
Contributors of blind wood can be aging wood, poor sunlight, environmental stress, slow spur renewal and vigorous vegetative growth, but the main mechanism that causes blind wood is apical dominance.
Apical Dominance
Apical dominance is the phenomenon where the topmost growing tip (apical bud) suppresses the growth of lateral buds along the stem. This phenomenon is caused by hormone balances of auxin and cytokinins.
The shoot tip produces auxin where auxin moves down within the plant. Auxin suppresses lateral bud outgrowth. Cytokinins come up from roots and promote bud break. The auxin:cytokinin ratio controls whether buds stay asleep or break dormancy.
It’s the auxin : cytokinin ratio that decides fate:
- Higher auxin → buds stay dormant
- Higher cytokinin → buds push to break dormancy
Modern high density systems can intensify blind wood behavior by encouraging early vigour and strong leaders, rather than focusing on blind wood prevention which can lead to long term production losses.
Although apical dominance is the main contributor to blind wood, higher auxin levels can be exacerbated by poor light distribution.
Poor Light Distribution
Shaded wood experiences reduced carbohydrate availability, which limits both floral initiation and bud survival. Peer‑reviewed research shows that buds exposed to prolonged low light either (i) fail to differentiate, losing viability, or (ii) remain paradormant, making blind wood more likely even if hormones are balanced.
This is not just about shade vs sun. In apple research, poor light distribution refers to:
- Strong vertical light gradients (bright tops with lower canopies)
- Horizontal shading from adjacent shoots or leaders
- Internal canopy light below functional thresholds
When light interception is too high or too uneven, internal canopy zones become functionally unproductive.
Growers often notice blind wood mid‑leader and in the interior of tall spindle systems, which aligns with documented light distribution patterns in apple canopies.
Poor light amplifies apical dominance because under shaded conditions:
- Auxin suppression is stronger
- Cytokinin response is weaker
Buds are less able to “push back” because they are weaker sinks, meaning they are less competitive for nutrients, hormones and energy.
This two‑way interaction explains why blind wood is most severe where strong apical dominance and shade coexist.
Unless we intervene, trees will pour growth and hormones into shoot tips and starve interior wood.
Mitigate Blind Wood
The best forms of blind wood prevention rely on continuous renewal of limbs, effective light penetration, stress reduction and vigour control.
Once those buds don’t push in year one, odds drop fast in remedying the wood section, where it could become semi-permanent blind wood.
Every mitigation tool for blind wood works by interrupting apical dominance, where most effective methods occur when tissue is young and is growing.
Scoring, Notching, Bending
Scoring uses a shallow cut through bark and cambium above a dormant bud. It has shown to have a mild effect and is often inconsistent.
Notching is the physical removal of a thin strip of bark above a bud, that removes a small strip of cambium. This creates a strong interruption of auxin flow, having higher and more consistent bud break in comparison to scoring.
- Timing: Bud swell to ~1–3-inch shoot growth.
Notching is labor intensive but is one of the most reliable tools for bud break. Peer‑reviewed studies show notching is significantly more effective than scoring, especially on one‑year‑old wood and when done a few weeks before bloom.
Bending is typically used to alter the crotch angle of young limbs, using material to make limbs more horizontal. This changes hormone distribution by altering shoot orientation. Bending reduces vigour, encourages flowering and weakens apical dominance
Research shows bending alone is unreliable at eliminating blind wood, it is helpful, but best used in conjunction with other methods, like pruning.
Plant Growth Regulators (PGRs)
Use of PGRs with other methods, such as scoring or notching improves the efficacy of bud break in blind wood. There are currently two products available for Ontario apple grower to improve branching: Maxcel and Promalin SL.
Cytokinins
Products like Maxcel, which contains 6-benzyladenine (6-BA)
- Mechanism: They work by increasing the cytokinin signal, shifting the auxin:cytokinin balance, ultimately promoting bud break
- Timing: Apply to actively growing shoots
- Typical window: ~1–3-inch shoot growth (early push) OR when shoots reach ~28–30 inches depending on the tree system.
Cytokinins & Gibberellins
Products like Promalin SL, which contains 6-benzyladenine and gibberellins A4 A7
- Mechanism: Cytokinin wakes up blind buds; GA helps them stretch into usable feathers instead of weak spurs.
- Timing: Best results come when buds are still responsive—around bud swell to early shoot growth.
- Typical window: ~1–3-inch shoot growth (early push)
PGRs only work when the tree is physiologically active and they don’t resurrect fully suppressed, older blind zones effectively. Also, you can spray all the PGR you want, if light isn’t there, the response will be inconsistent. PGRs work best for blind wood mitigation when:
- Apical dominance is already weakened
- Applied at precise timing (during active shoot growth)
- Multiple, early applications at targeted locations
- Used in combination with notching or heading
Pruning
Click pruning, developed by Stefano Musacchi from Washington State University, has shown to be promising for type IV cultivars to control vigour and reduce blind wood. Click pruning consists of heading one‑year‑old wood, forcing lateral bud break, and singling the limb the following season. It is a multi-year pruning strategy that has shown to reduce blind wood and stabilize yield in Cosmic Crisp when compared with bending alone.
For younger trees, remember the following when pruning for blind wood prevention:
- Don’t let the leader run unchecked
- Prioritize early feathering, not correction later
- Systems like tall spindle only work if you actively manage leader dominance and light distribution
Baler Twine Wrapped Around Trees
This one comes straight from the field. Wrapping twine tightly around a leader or limb mimics large‑scale notching, restricting phloem flow, reducing auxin movement (Figure 3). There are no peer‑reviewed apple studies directly testing twine wrapping. However, the concept aligns with known physiology as phloem interruption is proven to release paradormant buds.
Although this has proven to be effective, there are risks. Girdling is a strong possibility if baler twine is left unchecked or not removed shortly after bud break (Figure 3). Monitoring regularly is important and removing the twine after use is encouraged.
Filling Canopy Space
As a last resort, some growers have utilized methods to fill canopy space. Filling canopy space can be achieved by limb wrapping, limb control and neighbour tree sourcing. These blind wood strategies focus more on pulling wood from alternative areas to fit within the blank canopy window.
These strategies are not as effective as previously listed methods, as this can delay the problem and could cause more issues with overlapping limbs and vigour control of the tree or trees involved.
Limb wrapping involves taking young limbs from the same tree and fastening the growth around the blind wood area in hopes of future vegetative growth (Figure 4).
Limb control for blind wood occurs when limbs are left to grow and/or are manipulated to fill the bare space. This can be used as effective blind wood management, but consideration of shading, along with reproductive and vegetative growth should be considered.
Utilizing a neighbour tree’s limbs to fill in blank canopy spaces can decrease blind wood areas, but tree resources and vigour are factors to consider. If using this method be sure that the rootstock and cultivar are vigorous enough to balance vegetative and reproductive growth along with filling the space.
These strategies can be successful in filling blind wood areas but keep in mind that tree resources will change and may not go to where they are wanted when utilized.
Erika DeBrouwer
OMAFA Tree Fruit Specialist