Hollow stem male (Amsterdam Genetics dot com)
Introduction
Hollow cannabis stems are a common phenomenon that many growers misunderstand. Some believe they indicate superior genetics or increased potency, while others think hollow stems improve nutrient flow. None of this is true.
Hollow stems result from nutrient deficiencies—specifically calcium and boron—and are exacerbated by environmental stress. Far from being a sign of excellence, they’re a red flag for structural weakness in your plants. This post breaks down the myths, explains the real causes, and offers practical, science-backed solutions for growers using coco coir or hydroponic systems. Let’s fix hollow stems for good.
Quick Reference: Recipes for Success
| Amendment | System | Dosage | Purpose |
|---|---|---|---|
| Gypsum (Calcium Sulfate) | Coco | 3 g/L | Provides steady calcium and sulfur. |
| Bonemeal (Dicalcium Phosphate) | Coco | 1 g/L | Supplies calcium and phosphorus. |
| Wollastonite (Calcium Silicate) | Coco | 2 g/L | Adds calcium and silica. |
| Borax (11% Boron) | Coco | 0.5 g/L | Facilitates calcium transport. |
| Chelated Calcium (Ca-EDTA) | Hydroponic | 0.15 g/L | Delivers bioavailable calcium. |
| Solubor (20% Boron) | Hydroponic | 0.01 g/L | Enhances calcium mobility. |
Cross section of a hemp stalk (courtesy J. McPartland)
The Myths About Hollow Stems
Myth 1: Hollow Stems Are Genetic
Growers often blame hollow stems on genetics, claiming some strains are naturally hollow.
- Reality: Research in other crops, like broccoli and celery, shows hollow stems are caused by nutrient deficiencies, especially calcium and boron [1] [2]. Genetics only determine how susceptible a plant is under stress—not the outcome itself.
Myth 2: Hollow Stems Improve Nutrient Flow
The hollow pith in the stem might seem like a pathway for nutrients, but it plays no role in water or nutrient transport.
- Reality: Xylem and phloem handle all nutrient transport. Hollow stems weaken plants and make them prone to snapping under heavy yields [3].
Myth 3: Hollow Stems Indicate Potency
Some growers associate hollow stems with higher cannabinoid or terpene production.
- Reality: Potency is determined by genetics, light intensity, and stress—not stem structure [4]. Hollow stems do nothing to enhance potency.
The Real Causes of Hollow Stems
Calcium Deficiency
Calcium is critical for building strong cell walls. Without it, plant tissues weaken, leading to hollow stems [5].Boron Deficiency
Boron is essential for calcium transport. A lack of boron disrupts cell wall synthesis and causes structural issues [6].Environmental Stress
Excessive nitrogen, rapid growth, and temperature swings make plants more vulnerable to calcium and boron deficiencies [7].
How to Fix Hollow Stems
For Coco Coir Growers
Amending coco coir with the right nutrients during setup prevents hollow stems and strengthens plants. Here’s a tried-and-true recipe:
Gypsum (Calcium Sulfate): 3 g/L
- Provides slow-release calcium and sulfur for strong stems [8].
Bonemeal (Dicalcium Phosphate): 1 g/L
- Adds calcium and phosphorus to support root and stem development [9].
Wollastonite (Calcium Silicate): 2 g/L
- Supplies silica and calcium, improving stem rigidity and reducing the need for additional silica supplements [10].
Borax (11% Boron): 0.5 g/L
- Delivers boron to facilitate calcium transport and prevent hollowing [11].
Instructions:
- Mix these amendments evenly into pre-washed coco coir.
- Use the amended coco coir directly for planting—no soaking or buffering is required.
For Hydroponic Growers
In hydroponic systems, precise nutrient management is key to avoiding hollow stems.
Chelated Calcium (Ca-EDTA or Ca-DTPA): 0.15 g/L
- Ensures calcium remains bioavailable, even in high-phosphate solutions [12].
Solubor (20% Boron): 0.01 g/L
- Provides a reliable dose of boron to enhance calcium transport and cell wall integrity [13].
Instructions:
- Add chelated calcium and Solubor to your reservoir with every refill.
- Mix thoroughly to ensure even nutrient distribution.
Conclusion
Hollow stems are not genetic, beneficial, or a sign of potency—they’re a problem. They signal nutrient deficiencies and structural weakness that can reduce yields and compromise plant health. By amending coco coir with gypsum, bonemeal, wollastonite, and borax or optimizing hydroponic nutrients with chelated calcium and Solubor, you can eliminate hollow stems and cultivate stronger, healthier cannabis.
Fix your nutrient strategy today, and grow the robust, high-yielding plants you deserve.
References
- Xu, Y., et al. "Calcium and Boron Interplay in Plant Cell Wall Development." Journal of Experimental Botany, 2022, pp. 450–453. DOI.
- Haque, M., et al. "Nutritional Synergies in Structural Plant Growth." Plant Science Frontier, 2021, Section 4.2. DOI.
- Taiz, L., et al. Plant Physiology and Development. Sinauer Associates, 2015, Chapter 6.
- Backer, R., et al. "Cannabinoid Production Drivers in Cannabis." Frontiers in Plant Science, 2019, Figure 3, p. 210. DOI.
- Marschner, H. Mineral Nutrition of Higher Plants. Academic Press, 2012, Chapter 3, pp. 112–115.
- Raviv, M., et al. Optimizing Hydroponic Nutrient Formulas. Horticultural Reviews, 2020, Chapter 2, pp. 25–30.
- Springer, J., et al. "Preventing Structural Weakness in Broccoli." Plant Growth Regulation, 2022, p. 34. DOI.
- Wollastonite Use in Agriculture. Agricultural Science Journal, Section 2.3. Link.
- Borax in Nutrient Applications. Horticultural Science Guide, Chapter 5, p. 55. Link.
- Solubor Nutrient Application Guide. Horticultural Science Guide, p. 11. Link.
- Xu, Y., et al. "Calcium Transport via Boron Assistance." Experimental Botany Today, pp. 460–461.
- Haque, M., et al. "Hydroponics and Nutrient Bioavailability." Plant Science Applications, 2021, Section 5. DOI.
- Springer, J., et al. "Solubor and Calcium Uptake Efficiency." Agriculture Research, 2023, pp. 75–77.
Images are copyright by their respective owners and used here under Fair Use Doctrine.