5 Questions with Pierre-Marc de Champlain

Special Advertising Section - Ask the Experts: Growing Media

Pierre-Marc de Champlain, director of technical services for Berger, explains how to select the right growing mix for cannabis propagation.

July 7, 2021

1. Why is cannabis propagation a critical step in the production process?

The growing process truly begins with the seedling or the rooted cutting; therefore, if the young plants aren’t healthy and uniform, you’re off to a bad start. Inconsistencies can eventually even out, but they can also be amplified if the appropriate corrective measures aren’t implemented.

Selecting the appropriate growing mix is one important factor. Others include maintaining proper sanitation practices, humidity, air, light and temperature levels, fertilization and scouting programs, and more.

2. What is better, seeds or cuttings (clones)?

There are advantages and disadvantages to both. Although seeds are very expensive, growing from seed is less expensive than cuttings. However, even feminized seeds aren’t 100% reliable as they can contain up to 5% of hermaphrodites that can produce male flowers. These crops need to be identified and eliminated as rapidly as possible to avoid contaminations. Seeds aren’t necessarily identical clones and can exhibit some genetic variations. This can influence various characteristics such as productivity and harvest time.

Cuttings are a true genetic copy of the mother plant, which means all the sought-after attributes are transmitted without those pesky male plants. You also get a two-week head start compared to seeds. However, cuttings are more expensive to produce. You need to maintain your mother plant stock, keeping them healthy, and disease and pest free. Sanitation practices are critical because cuttings are very vulnerable to diseases before significant rooting has occurred.

3. Do both propagation methods require the same growing media?

You could use the same type of growing media, but it’s not necessarily ideal. Seeds need to be surrounded by a uniform layer of moisture to ensure adequate water absorption by the seed. This can easily be achieved with a fine-grade sphagnum peat moss. You also want to include some perlite to provide drainage and avoid oversaturation. For smaller cavity trays (less than 72 cells), a fine-grade perlite is preferable to make sure the cells are filled uniformly without bridging. A fine-grade vermiculite can also be included to improve water distribution and C.E.C. (ex: BM2 Seed Germination).

For larger cavity trays (more than 72 cells), you may want to consider propagation mixes with a coarser grade of perlite for additional structure and drainage (ex: BM2 PPP or BM2 20P).

You also want to maintain uniform soil humidity for cuttings, but they are even more sensitive to oversaturation and require a more porous growing media. The same growing media used to germinate seeds in larger cavity trays is ideal to root cuttings (ex: BM2 PPP or BM2 20P).

4. What if I want to direct stick into larger containers?

I wouldn’t recommend this for several reasons. First, you would need a mix with a coarser grade of peat moss to get the drainage needed for the later growth stages of production. This won’t allow you to create the ideal environment for root initiation. You run the risk of a higher-percent mortality, which means wasted space, resources and labor. If this is your only option, there are several mix options that are available depending on the desired characteristics (ex: BM6 HP and BM5 HP). Rooting hormones are a must.

5. What is the most desirable characteristic for my growing mix?

Uniformity. You select a growing media because it provides specific physical and chemical properties, but these properties need to be uniform to consistently achieve predictable results. How you handle growing media is also critical. If the fibers are overly damaged during the tray/pot-filling operations, or if the mix is significantly compacted, the desired air-to-water ratio will be compromised.

Learn more: cannabis.berger.ca