The world’s most sought-after cannabis seeds command some truly sky-high prices. A single seed of the most unique, high-performing cannabis genetics can now cost upwards of $50 and sometimes north of $100 per seed in exceptional cases! Whether you’re breaking the bank on your latest acquisition of top-shelf cannabis genetics or opting for more regularly-priced cannabis seeds, the best way to honor your financial outlay—as well as the years of painstaking selections claimed by the professional cannabis breeder—is to give your cannabis seeds the very best start in life. All well and good, you might say, but what does this really mean in practical terms? 

The Paper Towel Seed Starting Method is Outdated

Let’s get this out of the way first. While germinating cannabis seeds within the careful folds of a moist paper towel is still a common practice among hobbyists, it’s no longer common in commercial cannabis cultivation settings. For one thing, transferring germinated seeds from the paper towel to the growing medium can easily damage delicate taproots and increase the risk of contamination. Direct sowing into Grodan A-OK starter plugs is easier, safer, and more efficient. Some cultivators pre-soak their cannabis seeds in plain, room-temperature water for 12 to 24 hours before sowing in an effort to speed up germination, but it’s not strictly necessary.

Choosing the Ideal Propagation Media for Cannabis Seeds

Selecting a growing media that is perfectly suited to cannabis propagation is just as important a decision as the cannabis genetics themselves. Stone wool is the commercial cannabis cultivator’s go-to for providing their seeds with the ultimate ‘crib’ for several key reasons. The fibers inside a Grodan A-OK starter plug have been carefully bound together at a precise density to allow tender new roots the ideal balance of physical anchorage and ease of exploration through the medium. Grodan A-OK starter plugs are firm enough to be easily handled by employees while mitigating the risk of inadvertent root damage. Perhaps most importantly, stone wool is exceptionally good at providing the optimal balance of air and moisture to young seedlings, which are particularly sensitive to both overly dry and wet conditions.

Infusing Stone Wool with the Perfect Nutritional Balance

Grodan plugs are designed for fast, uniform propagation of cannabis cuttings and seedlings. They won’t degrade or start composting like soil, peat, or coco coir, even if stored for decades. Neither do they harbor pests, pathogens, or other diseases. Instead, Grodan A-OK plugs provide a perfectly blank canvas for your propagation feed solution. And, thanks to stone wool’s super-low cation exchange capacity (CEC), what you give your seedlings is what they get! On the other hand, cultivators using coco coir plugs, for example, understand all too well the medium’s tendency to readily exchange residual potassium with calcium in the feed solution, leading to cation imbalances when growers least want them.

Keep a Close Eye on Microelements

Once Grodan A-OK starter plugs have been pre-soaked in a mild nutrient solution, seeds can be inserted straight away. They don’t need to be left to drain like larger grow blocks.

Even in a soilless media, it’s easy to overfeed seedlings. Stone wool is a smart choice for cannabis cultivators because the nutrition levels can be precisely calibrated with the initial pre-soak solution. Growers use very dilute nutrient solutions in the propagation stage (typically between 250 and 400 PPM or 0.5 and 0.8 mS/cm). At these dilution levels, it’s important to keep a close eye on micronutrient levels (e.g., iron, manganese, zinc, boron, and molybdenum) to ensure they remain adequate. Specialist starter nutrient products with elevated micronutrients are sometimes used to help mitigate this issue. Alternatively, a common ratio for using three-part nutrients during the propagation phase is 1:2:1 grow:micro:bloom. Some cultivators choose to add a specialist trace element supplement instead.

Download Propagation of Cuttings Chapter

Whatever Growing Medium You Choose, Don’t Rush the Propagation Stage

An A-OK starter plug can typically support a cannabis seedling for about 10 to 14 days before it needs to be transplanted. During this period, the seedling will develop a robust root system and its first true leaves. Wait for the roots to emerge from both the bottom and the sides of the plug, usually when the seedling has 2-3 sets of true leaves. Starter plugs can be easily and evenly re-moistened with a quick dip in feed solution. If daily dips are required, this is a good indication that the seedling is ready to be transplanted into a larger grow block or its final growing medium. Delaying transplant beyond this period can result in the seedling becoming root-bound, which could stunt growth.

One final point: starting your seedlings in stone wool doesn’t necessarily lock you into using stone wool for the entire grow. While Grodan Gro-Blocks are highly recommended for the next stage, many cultivators use A-OK starter plugs to produce hundreds, sometimes thousands, of healthy and uniform seedlings before transplanting into their preferred loose-fill media.

Looking to optimize your investment in premium cannabis genetics? Grodan offers a wide range of propagation products tailored to your needs. From the versatile A-OK starter plugs available in various sizes to suit different crops and growth stages, to our highly durable Gro-Blocks, Grodan’s propagation solutions are designed to give your plants the best possible start.