1. What attributes are important when selecting a growing mix for hemp seed propagation?
Seeds need to be surrounded by a uniform layer of moisture for the imbibition process to begin. The best way to create this environment is with a blend of fine-grade peat moss, perlite and vermiculite (e.g., Berger BM2 Seed Germination). The small particles of peat moss and vermiculite help maintain a high moisture content, while perlite ensures the media isn’t oversaturated. Using a germination chamber is not necessary as long as you maintain a warm and humid environment during the germination process. In fact, hemp seeds germinate well in the presence of light. If you are using larger cavity trays (more than 72 cells, for example), you may want to consider using a coarser grade of perlite (BM2 20P) to improve porosity.
2. What about cuttings?
Additional drainage is also preferable when propagating cuttings. Cuttings typically root very well in clean and slightly more porous growing media. A combination of fine-grade peat moss and coarse-grade perlite gives great results (e.g., Berger BM2 PPP or BM2 20P). Hydrating the mix helps not only stimulate root initiation but also improve water distribution during initial irrigations. Hemp cuttings shouldn’t be watered thoroughly after sticking. The base of the cutting needs oxygen, otherwise the stem may rot.
3. How will the composition of the growing media in later growth stages differ from the propagation phase?
The particle size of the ingredients must be larger in later growth stages to provide excellent drainage and increase air space. This allows growers to be much more precise with their fertilization and easily steer the crop during the vegetative and flowering stages. Growers have had great success with Berger’s classic peat perlite blend (BM6 HP) or a combination of peat, perlite and wood fiber (new BM5 HP).
4. What other factors should growers consider when selecting growing media?
Growing media selection will depend on several factors, including the climate zone, season, water source, irrigation method and container size. Each ingredient used in the growing media has its specific purpose, and the mix ratio can be adjusted to enhance certain characteristics:
- Professional/coarse-grade sphagnum peat moss helps increase both water/nutrient retention and porosity. It also improves cation exchange capacity (CEC).
- Horticultural/coarse-grade perlite provides additional air space.
- Coarse-grade NF Wood (Berger’s wood fiber product line) improves both drainage and water retention.
- Coir chips help provide additional air space but also can hold a significant amount of water. Be sure to wash coir to avoid high salt content and a massive release of potassium during initial fertilization.
Whether for propagation or finishing, growing media quality will have a direct impact on final output. Without a uniform mix, it is very difficult to manage production and obtain predictable results, especially within a large operation. Inconsistent growth can be very hard to correct and will directly affect your bottom line. Don’t be afraid to invest in your substrate; it will be worth it in the long run.
5. Why should growers consider finishing production in a controlled environment?
Mature hemp seedlings or rooted cuttings are typically transferred to the field to finish. However, in high-value markets like pharmaceuticals, there has been a push toward finishing hemp in a controlled environment. Obviously, this requires more capital investment, but the benefits include year-round production, faster turnaround and fewer pest problems. In indoor production, young plants are transferred into a more porous growing media for better control of the growing parameters.
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