Why are my cannabis seedlings growing so slow?

Slow growth of your cannabis seedlings may be nothing to worry about so long as your basic grow room conditions are within spec. It may take a couple of weeks until the seedling looks reasonably well established. But make any rookie mistakes with the environment, cannabis seed germination, nutrients, lighting etc and you can stunt the seedling slowing growth. Depending on the extent of the damage done, this may have significant impacts on final yield and quality. Our guide explains all you need to know about seedling care and what to do if you think growth is simply too slow.

How long does it take for cannabis seeds to germinate?

Most cannabis seeds germinate within ~2-4 days. Very occasionally it can take up to a couple of weeks. Once the seeds have germinated, they have all the genetic information they need to complete growth, you just need to ensure optimised conditions and avoid stressing the young plants.

Can you speed up the germination process?
Unfortunately not. All you can do is use a consistently reliable cannabis seed germination method. Whether you use autoflower seeds, feminised seeds or regular cannabis seeds you will have to wait roughly the same length of time for cannabis seed germination to occur.

Stunted cannabis seedlings growth: causes and cure

Stunted cannabis seedlings are often the result of the seedlings having to battle through adverse conditions. Of course, you could get very unlucky and simply have a weird dwarf plant. But if you’re buying proven cannabis seeds from a top supplier this risk is minimal.

Low-quality cannabis seeds

Even professional, licensed master growers will struggle to achieve respectable results if forced to grow second-tier cannabis seeds. If all cannabis genetics had 25% THC potential it would be easy to choose the right seeds for your next grow. In reality, most growers spend quite some time researching different seed suppliers, checking out their grow reviews and finalising their strain choice.

Grow the best cannabis seeds you can buy and be sure to check out as many online customer grow reviews as you can find. Dutch Passion has the biggest archive of customer grow reports & grow guides. Check them out, along with the many thousands on social media.

If you are simply looking for the cannabis seeds with the highest THC potential, then you will be pleased to know Dutch Passion have done all the hard work for you. Only our very finest strains are selected to be included in the revered Dutch Passion High THC cannabis seed collection.

Cannabis seed germination method

The two most reliable methods are to start the seeds directly in the grow medium (e.g. moist soil) or to germinate between two damp cotton pads. If you want to aim for the highest cannabis seed germination rates, we recommend you try the damp (but never soaked) cotton pad method.

Watering and pot size issues

One issue consistently seen by less experienced growers is the tendency to over-water their cannabis seedlings. This creates an excessively damp root zone coupled with depleted oxygen levels. Cannabis roots require oxygen to grow and thrive, they can’t do this with water-logged roots. Use of large, highly aerated grow containers such as airpots or fabric grow sacks give great results.

Keeping a plant in a container which is too small will also stunt growth since the root mass is unable to grow sufficiently to support growth. If you do progressively increase the size of your growing container, this includes many soil & coco growers, ensure that you don’t leave it too long and suffer from root-bound plants.

Damping-off / Fungi disease

‘Damping off’ is a disease which can be caused by several different fungi and fungus-like organisms. It causes a thin, shrivelled stem which is unable to support the seedling, often killing it. Although rare, it’s a nuisance for growers. Good levels of tent cleanliness, removal of old plant/grow material, regular tent vacuuming, and regular tent cleaning are the best tips to avoid damping off disease.

Temperature issues

Most growers try to aim for lights-on temperatures of around 25ºC (around 75-77F), perhaps a couple of degrees lower during the dark period. Trying to grow at temperatures too high or too low will slow down growth and introduce other issue too (such as nutrition problems, mould in late bloom etc).

pH issues

Although less of an issue for soil growers (soil tends to buffer pH), pH is important for hydroponic growers. If the pH is outside the preferred range (typically around pH 5.8) then nutrient lock-out can occur, stunting your plants and slowing growth. Nutrient lock-out can occur even if the necessary minerals are present, since they are not bio-available if pH is too acidic or alkaline.

Lighting issues

If lighting intensity is too high the seedlings may struggle to grow. This type of issue is most likely to be seen by less experienced growers using powerful new LED grow lights and simply overloading the photosynthetic capability of the delicate young seedling plant tissues. Leaves may discolour and growth will slow or grind to a halt.

Most quality LED grow light manufacturers have detailed guidelines for the power levels and light hanging-heights at different stages of growth. If you can keep your plants in the optical sweet spot (optimised light levels) from cannabis seedling to harvest, you are optimising one of the most important aspects of plant growth. If you can ace nutrient control as well, you can consider yourself an experienced grower….

Nutrient issues

One of the greatest skills that a grower can acquire is the ability to keep their cannabis plants in the nutrient sweet spot from seedling to harvest. That means avoiding the perils of under-feeding as well as the beginners’ favourite error of over-feeding their plants.

With insufficient nutrients, the seedling will struggle to grow. Conversely, too many nutrients in the grow medium will damage (or ‘burn’) the delicate root system. This can cause permanent damage resulting in dwarf plants. Small cannabis seedlings need relatively little nutrition, as many less experienced growers find to their cost.

Anyone that routinely struggles with the admittedly difficult art of keeping their plants in the nutrient sweet spot may want to consider growing with slow-release organic nutrients, such as those from BioTabs. This means the grower only needs to add water during the grow, greatly simplifying matters. All that may be required are some additional feeds of bloom nutrients in late bloom if the plants look hungry.

Note: Always ensure that your feed/water solution is at room temperature. Preparing feed solutions with cold tap water and using it on your plants will cold-shock the roots and slow down the growth of your plants.

Damaged tap root/root system

Experienced growers know that there is little to do during the early stages of seedling life. Resist the temptation to pull a stuck seed shell off your seedling leaves - it usually comes off on its own accord. Likewise, the root system is very fragile. Pot-up your plants incorrectly and you can accidentally lose some of the crucially important root mass. If this occurs your plant may be temporarily (or even permanently) stunted as it diverts biochemical attention to fixing and re-growing a compromised root system.

Take care of your cannabis seedlings!

Getting your seedlings off to a healthy, strong start is the best way to begin a cannabis grow. It’s neither difficult nor daunting, so long as you avoid the most common errors. Remember, thousands of people successfully harvest their plants each day, for most people growing cannabis is great fun, rewarding and relatively easy.

If you would like a deeper dive into this, you may find the detailed guide (below) useful reading.