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Slow Cannabis Plant Growth And What You Can Do About It

When your cannabis plants grow slowly or stop growing altogether, there is always a reason. It could be a problem with nutrients, an environmental factor, or something else entirely. Let’s explore the reasons your cannabis plants or seedlings may experience slow or stunted growth.

“Why are my plants growing so slow?”. Sometimes, marijuana plant problems occur out of the blue. Your baby may not have shown any signs of an issue, but now you notice that development has halted and have no idea why. Here are some possible factors behind the slowed growth of your cannabis seedling or plant.

18 REASONS FOR SLOW OR STUNTED CANNABIS GROWTH

1. SEEDS ARE OLD OR LOW-QUALITY

Old seeds don’t just take longer to germinate (if they germinate at all); plants grown from aged seeds can also sometimes grow at a reduced pace. Likewise, good genetics are essential for healthy and vigorous growth from seed to harvest. A random bagseed will not perform nearly as well as quality seeds obtained from a reputable seedbank.

2. CLONE STRESS

Sometimes cuttings don’t root well, which hampers their growth. To prevent this from happening, apply a little bit of rooting hormone immediately after taking your cuttings.

Also, make sure your environment promotes root growth. The medium should be humid (but not too moist) with a pH level of about 6.0. Keep your cuttings at a temperature of around 22ºC. If they get too cold, they won’t root at all, and if it’s too hot, the roots will die.

3. ROOT HEALTH

When your plant’s roots can’t receive enough oxygen, metabolic functions slow down. In some cases, a lack of oxygen may stop their growth altogether. One common reason for this is overwatering or using substrates with poor drainage.

What to do about it? Create a light and airy growing medium with good drainage. You can improve poor-draining soil by adding some perlite.

The root zone for your cannabis plants should never get much hotter or colder than room temperature. Likewise, physical damage to the roots, mould, or bacteria can severely affect the growth of your plants. Always use non-transparent planters so light doesn’t reach the roots, as this is bad as well.

4. CANNABIS PLANTS STRETCH TOO MUCH

Stretching among seedlings can be particularly problematic. Multiple factors can induce this response, but the most likely culprit is a lack of light.

If your seedlings are spindly, increase light intensity or bring the lights closer. Prop them up with dowels as an aid during recovery. As a last resort, you can (carefully) replant them deeper into a new pot.

5. PLANTS ARE NOT GETTING ENOUGH LIGHT

Although requirements can vary from strain to strain, light is nonetheless a critical factor for the development of all cannabis plants. A lack of “good” light can absolutely lead to slowed growth. If you grow indoors and suspect that your plants aren’t getting enough light, try to decrease the distance between your lamps and the tops of plants. If you grow outdoors in pots, move your plants to a sunnier spot.

6. PLANTS ARE GETTING TOO MUCH LIGHT

Any type of stress on your cannabis plants, including many hours of exposure to direct sunlight without rest, can also halt or slow down growth. If you grow indoors and suspect light exposure to be the source of stress, decrease the intensity or move lamps further away from the canopy if possible. Know that seedlings are particularly sensitive to intense light! If you grow outdoors and you’re able to, move your plants into a spot where the light is diffused, such as around a shade tree.

7. INCORRECT LIGHT SPECTRUM

How fast and how vigorously plants grow are influenced by the spectrum of light they receive. Make sure you use the correct type of light according to each stage of growth. For healthy vegetative growth, you want a cooler light with more blue in its spectrum, a so-called “vegging light”. Lights with a warmer, more reddish spectrum are used for the flowering phase.

8. LIGHT STRESS: DARK CYCLE INTERRUPTION

Light is essential for all plants to grow. Any changes in light intensity or exposure will have an effect on growth. Flowering cannabis is especially susceptible to interruptions in the dark cycle. A light leak in your tent, stray light from a street lamp, and even a red light from a camera can disrupt flowering, and in a worst case scenario, can turn plants hermaphroditic. For that reason, it is very important to maintain complete darkness during the lights-off hours.

Exposing weed plants to irregular light hours can cause a hormone imbalance that confuses their internal clock. Your plants could flower prematurely, or they could revert back to the vegetative stage. If this happens, growth and yields will greatly suffer. For that reason, make sure to keep your light cycle consistent.

The above suggestions predominantly apply to photoperiod strains, as autoflowering cannabis flowers based on age rather than light exposure.

9. OVERWATERING

Overwatering is one of the most common mistakes made by new cannabis growers. It’s like suffocating your plants, and one of the main reasons behind slow growth, nutrient deficiencies, root rot, fungus, and many other problems. Don’t water too often and do not water on a fixed schedule. It is better water less frequently so that the soil can dry out between waterings. A good way to test whether you should water or not is to lift up the pot itself. If it feels quite light, it is time to water again.

10. NOT ENOUGH NUTRIENTS

Although not as common as overfeeding cannabis plants, an insufficient amount of nutrients for healthy growth can well be the reason for slow growth. Know that the nutrients found in most commercial potting mixes will only last for 3–4 weeks; afterwards, you will have to administer some more quality nutrients. Check the label of your nutrient products for the recommended dosage for healthy growth. Also know that your plant’s nutrient requirements are closely linked to the light intensity your plants are exposed to. Plants under intensive lights grow faster and will require more nutrients than plants under fluorescent lights, for example.

11. CALCIUM DEFICIENCY

Calcium is among those vital elements that your plant needs for healthy development. A lack of calcium can manifest in the following symptoms:

  • Fresh growth is slow, twisted, and curled
  • Young shoots are discoloured and turn purple or yellow
  • Overall plant growth is slow and lacks vigour and vitality
  • You can avoid a calcium deficiency by adding dolomitic lime to your soil or growing medium

Address a calcium deficiency immediately with commercial CalMag products that contain liquid calcium. You can add these products to your nutrient solution or administer them as a foliar spray.

Be aware that some growing media, like coco, increase the risk for a calcium deficiency. If you grow in coco, you should use special coco nutrients and/or regularly add CalMag to your nutrient regimen.

12. INCORRECT PH LEVEL

Incorrect pH level of your nutrient solution is among the most common reasons for cannabis growing problems, including slow growth. The reason for this is that cannabis thrives only in a relatively small window of suitable pH values. If the pH is off, the plants are unable to take in nutrients, even if they are present.

Make sure to dial in the correct pH level depending on your growing method. If you grow in soil, make sure the pH level is from 6.5 to 7.0. If you grow in hydro, an optimal pH level is 5.6 to 5.8. For soilless grows, such as coco, a pH level of 6.0 to 6.3 is optimal.

13. TEMPERATURES ARE TOO LOW OR TOO HIGH

Cannabis likes it warm to grow healthy, and does best at daytime temperatures between 25–30°C. Temperatures lower than that will slow down your plant’s metabolism, resulting in slower growth. But excessive temperatures are not optimal either. At very high temperatures, heat stress can also slow down or even halt plant growth altogether. If you grow indoors, adjust your temperature to a comfortable level. You can also provide some cooling with fans that blow a mild stream of air over your plants. This can also help prevent hot air pockets from forming inside your grow room.

14. PLANTING POTS ARE TOO BIG

Cannabis growers often start their seedlings in small cups. Later on, when the plants have reached an adequate size, they will “pot-up” to larger containers.

If you start your cannabis plants in containers that are too big, there is a high risk that you’ll overwater them. The issue is that seedlings cannot absorb all the moisture that is held in a large container, unlike mature cannabis, which can “drink” much more. Furthermore, a large pot will also take much longer to dry out.

To avoid the problems that come with too much soil and moisture, start seedlings in smaller containers until they’re growing vigorously. Once they have a set of 5–6 real leaves (not counting the cotyledons), then transfer them to a larger container, at least twice the current size.

If your seedling is already in a big container and you don’t want to or can’t move it into a smaller cup, water only a small area around the seedling.

• What Is The Right Size Pot For Your Cannabis Plant?

Use this rough guide to determine what size pot you should use for your cannabis plant:

  • Plant height 30cm: 7.5–11l container
  • Plant height 60cm: 11–19l container
  • Plant height 90cm: 18–26l container
  • Plant height 120cm: 22–37l container
  • Plant height 150cm: 30–37l+ container

15. STRESS CAUSED BY PESTS / DISEASES

Insects, pests, and disease can cause damage and compromise a plant’s immune system. In a best case scenario, your plant may survive, but you will have poor yields. In the worst case, your plants could die.

Insects may feed on the leaves, affecting a plant’s ability to retain water and transpire. Other pests may damage the roots or cause additional problems. Any time your plant is sick or infested with insects, it will spend most of its energy defending itself and recovering from damage, which will slow down growth.

If your plants are infested, you’ll want to treat them immediately with appropriate measures. Even better, you can use preventative methods (e.g. neem oil, slug barriers, etc.) to minimise the risk for pest infestations. During all stages of growth, ensure that you regularly check for symptoms of pest infestations, including under the leaves.

16. STRESS CAUSED BY TISSUE DAMAGE

Physical damage, such as broken branches, can significantly slow your plant’s growth. Any damage will make the plant redirect valuable resources to repair wounds—resources that could be better spent on growing or flower production.

If you’re growing outdoors, situate your plants in an area sheltered from strong winds and heavy rains, and use chicken wire and stakes to maintain support.

Seedlings and young cannabis plants are especially vulnerable. Allow your seedlings to mature indoors for some weeks before setting them outside.

17. STRESS FROM CANNABIS TRAINING TECHNIQUES

Tissue damage from high-stress plant training techniques always causes some delay in plant development. But when you’re pruning excessively or too frequently, your plant may ultimately spend more energy repairing itself than growing.

If you plan on pruning, don’t overdo it. Be aware that each pruning can delay the development of your plant for days, if not weeks.

If you’re using other plant training techniques such as topping, make sure you start as early as possible. If you’re growing autoflowers, don’t use any plant training techniques that involve tissue damage, such as pruning and cutting.

18. AGE STRESS

Older cannabis plants have different nutritional requirements than young plants. Their tissues become hard and woody, they’re less vigorous, and they’re unable to take in as many nutrients.

Because of this, you’ll want to adjust your feeding regimen accordingly. Otherwise you risk overfeeding, which in turn results in stunted growth, deficiencies, and disease. Keep this in mind if you’re keeping mother plants around for a long time.

Why is my cannabis plant growing slowly or not at all? Find out the answer to this question and see what you can do to solve it.

How To Get To Harvest Faster

“I need to harvest as soon as possible. What’s the fastest growth method? What can I do to speed up the time to harvest?”

How to Speed Up Harvest Time

Many of our readers write in to ask about speeding up the time to harvest.

So, how long does it actually take to grow marijuana?

Short Answer: From Day 1 of your marijuana plant’s life to a smokable harvest, you are looking at a window ranging between 3 and 7+ months!

Many factors will affect the total time, but the average grow takes 3-4 months. Learn more about the marijuana growth timeline.

Long Answer: These factors have the greatest impact on total time to harvest:

Plant strain – strain has the largest impact on growing time.

Desired yields – do you want to grow a few grams, a few ounces, or a few pounds?

Growing method – differing grow methods/setups can add or subtract a few weeks or even months!

7 Tactics To Get To Harvest As Quickly As Possible

Faster is not always better, but there are ways that you can speed up the time from seedling to harvest without sacrificing quality, potency or yields.

So today I’d like to share a short guide on how you can reduce the time to harvest, and how you can reduce the amount of time you actually spend tending your plants, and still get outstanding results.

If you’re serious about getting yields as quickly as possible, then these tactics will get you there the right way! Let’s get to it!

1.) Fewer Hours of Light Each Day in Flowering Stage

With photoperiod (regular) strains, you can manipulate the light schedule in the flowering stage to get buds to mature faster. Although most plants will start flowering when they get less than 13 or 14 hours of light a day (that’s when plants usually start flowering outdoors), it can take them a long time to “finish” and be ready to harvest with days that long.

Because of that, it’s recommended to give plants 12 hours of light each day, and 12 hours of dark to get the plant to start flowering, because plants usually finish maturing in about 8-12 weeks after the switch to 12/12.

However, some Sativa and Haze strains are from the equator, and they may not flower properly under a 12/12 light schedule. In that case, a grower can give a plant 10 or 11 hours instead of 12 hours of light a day, like a 11/13 or 10/14 schedule. This will cause the plant to finish flowering faster. In fact, this can be done to any strain to get it to finish flowering faster.

Give plants only 10 or 11 hours of light a day to get buds to mature faster

The one downside is that a shorter flowering stage with less hours of light each day mean that buds get less time to fatten and you will end up with smaller yields. Therefore it’s not recommended to try to get a plant to finish flowering in less than 8 weeks, as you’ll end up with very small yields. This technique is best used if you have a plant that’s been flowering for 2-3 months and doesn’t look like it plans on stopping any time soon.

How can this technique reduce yields? ​The less light you give your plant overall during its life, and especially in the flowering stage, the less your yields will be in general. A strain that takes longer to finish flowering usually produces bigger yields than a short-flowering strain because it gets so many extra light-hours where it’s making energy and fattening buds.

On a similar note, an auto-flowering plant gets pretty great yields considering it goes from seed to harvest in just 3 months. A big part of that is because they get 18 hours/light a day during their entire flowering period (compared to only 12 a day for regular plants)/ This gives the plant more light each day to produce buds, resulting in bigger yields.

2.) Choose A Quick-Finishing Strain of Marijuana

As you probably know, the life cycle for all marijuana plants is separated into two parts: the vegetative stage and the flowering stage.

The vegetative stage can be shortened by getting the plant to grow faster when she’s young. Yet the length of the flowering stage (the time between when flowers first start forming and when the plant is ready to harvest) is pretty much strain-specific.

That means that once you’ve started flowering a specific strain, there isn’t a whole lot good options to speed things up during the flowering stage.

Note: There are special light schedules, that involve lowering the amount of light each day in the flowering stage, which can sometimes get harvest to come a little quicker. For example a 10-14 schedule (10 hours light, 14 hours dark each day) during the flowering stage may get plants ready to harvest a week or two sooner for some strains, but lowering the amount of light each day combined with harvesting sooner really hurts your yields.

Many Indica hybrids (such as AK-48 and Northern Lights) naturally have very short flowering periods of only 7-9 weeks, which is a shorter flowering time than most other strains.

Hazes and Sativas often take much longer. For example a haze strain (like Haze 1 from Nirvana) can take 3-4 months in the flowering stage before being ready to harvest.

Every different strain has pros and cons, but if time is a factor for you, pay close attention to the length of the flowering stage when deciding which strain to grow. The majority of seed banks list the length of the flowering period as part of their stats for each strain.

Some strains are ‘auto-flowering’ and go through their whole life cycle regardless of light cycle or anything you can control. These strains tend to be ready to harvest in only 2-3 months from seed (though you should definitely expect smaller plants with relatively small yields when choosing an auto-flowering strain).

Auto-flowering strains of marijuana contain higher levels of CBD, a cannabinoid which has been associated with many medical benefits. So they may be the perfect choice for a medical marijuana user who needs to harvest quickly.

Also, check out my recent autoflower grow if you want to see autos in action…

In this auto-flowering grow, I harvested more than 6 ounces in less than 3 months!

3.) Give Plants 24 Hours of Light per Day During the Vegetative Stage

As long as you give your plants more than 14 hours of light a day, they will stay in the vegetative stage. But if you give the plant more light than that, they have more time in the day to grow!

Some growers believe it’s better to give marijuana plants 18 hours of light a day max, with a 6 hour dark period during the vegetative stage.

This is because plants grown under 18/6 tend to be more resilient to problems. If you have a sick plant, just reducing the light period and/or light intensity a little bit can help it recover faster.

Regardless of which is best for plant health, it’s a proven fact that marijuana plants given a full 24 hours of light a day will grow at least a little faster during the vegetative stage (however, you may consider back down to 18/6 if your plant is sick to help it recover from problems faster).

Therefore, if a short time to harvest is of the utmost importantance to you, you may want to consider going with the 24 hour light period during the vegetative stage for fastest growth. Again, this won’t make the plant’s flowering stage go any faster, but it enables you to start the flowering stage a little bit sooner. Speaking of which…

4.) Initiate The Flowering Stage Sooner

You may not realize that regular (non auto-flowering) marijuana plants can be flowered directly from seed.

When I say “flowered,” what I mean is that you can change the light schedule so that it forces your young seedlings to start making buds right away.

You can get a marijuana plant to start flowering by ensuring that it gets 12 hours of uninterrupted darkness each night, often referred to as the 12-12 light schedule.

This makes the plant “think” winter is coming, and it’ll start making buds as soon as it’s able. This means that your “flowering stage countdown” begins within about a month from the seed being planted.

So for example, Northern Lights has a flowering stage length of about 8 weeks. If you flowered a Northern Lights strain plant from seed, your buds would be ready to harvest in about 11-12 weeks.

Some growers will also flower marijuana clones as soon as they have formed roots, for basically the same effect, though clones tend to start flowering a little faster than a plant put on 12-12 directly from seed.

That being said, flowering from seed is a very inefficient manner of growing. Plants flowered from seed don’t get enough time to grow stems where buds form.

If you want to initiate flowering early, it’s better to do so after after waiting just a bit, so you grow plants that are relatively small but can produce more than a couple of grams worth of bud. This is known as the “Sea of Green” (SoG) technique. A bunch of smaller plants is easy for new growers to manage, plus it gives you the option of trying different strains instead of getting of lot of one strain.

5.) Grow Indoors

Growing outdoors can be more convenient and vastly cheaper for those who happen to live in a place with great growing conditions since the sun and nature are doing a lot of work for you. But outdoor growing isn’t the fastest way to grow and harvest your crop. Though there is an exception….

Outdoors, you must plant in the spring, and wait until late fall to harvest. That means that oudoor grows can take 6+ months. Given the right conditions (high-yielding strain, direct sunlight all day, good soil, avoid pests, etc) you can grow huge plants in that time, that produce pounds of buds.

Yet growing indoors gives you the ultimate control over how big your plants get, how long to keep them in the vegetative stage, and exactly when they start flowering amongst other things. You also have a lot more control over how much bud you’ll end up yielding.

With a well-chosen strain and a good setup, one can harvest several ounces of buds in less than 4 months indoors, which is nearly impossible to do outdoors in the same timeframe.

On a similar note, you might want to consider hydroponics over soil.

You can get faster vegetative growth with almost all hydroponic methods compared to what can be achieved with soil. That means that you could speed up time til harvest by using Deep Water Culture (DWC), Coco coir/perlite, or pretty much any non-soil growing medium. During the flowering stage, this isn’t as important, but this can shave weeks off your vegetative stage time (get straight to growing buds sooner!)

In my experience, top-fed Deep Water Culture hydroponics (also called ‘bubbleponics’) has given me the quickest growth of any hydroponics system I’ve tried.

6.) Pay Attention To Your Plants and Quickly React to Problems

I know this sounds like it doesn’t need to be listed, but it’s a more important job than people think. Every time your plants get sick, it slows down their growth while they try to recover. Every problem your plant runs into can add days or even weeks on to your total grow time.

Simply put: fixing a problem quickly equates to shorter time to harvest.

Plus, by reacting quickly to problems, you will save yourself the stress of trying to deal with a huge problem that’s gotten out of control since you’ve been watching out and adjusting along the way. We all know that problems tend to get much worse when left unchecked!

The more you tend to and baby your plants, the better they will grow, and the faster you will be able to harvest.

For example, the following plant problems will add time onto your grow

  • nutrient problems or a pest infestation can dramatically slow down growth, especially for young plants
  • heat stress or light burn can not only slow down growth in the vegetative stage, they can prevent buds from maturing properly in the flowering stage
  • accidentally re-vegging your budding plants will stop buds from maturing

7.) Make Sure You’re Feeding Plants The Right Type of Nutrients During Each Stage of Growth.

In the vegetative stage, it is important that you give your plants the right nutrients needed to get optimal growth.

Now if you’re starting with a good soil (Fox Farms Ocean Forest soil is a proven choice), you may not need to supplement any nutrients for the first 3-4 weeks, as the nutrients you need are already in the soil.

If you’re growing hydroponically (directly in water, or in a soil-less medium like coco coir), it is essential that you provide all the nutrients your plant needs right from the beginning.

You’ve probably seen ‘N-P-K’ numbers on the bottles of pretty much every nutrient line there is. These number are important to know since cannabis plants use more N (nitrogen) in the vegetative phase, and relatively more P & K (phosphorus & potassium) in the flowering phase. Conversely, giving your plant too much N in the flowering phase will actually slow down bud production. This means that you will harvest smaller yields of less-dense buds in addition to waiting longer for said buds!

This is why you need to either mix your nutrients by hand, or choose a nutrient system that is specifically formulated for the flowering stage of a plant like marijuana. By providing the right nutrients at the right time, you’ll reduce your overall time to harvest.

How Much Time Per Week Does It Take To Grow Cannabis?

Now that you’re equipped with the information to get you to harvest as soon as possible, let’s quickly address another common question we receive about time.

Growers often write in to ask us how much time it will take per week to grow a marijuana plant. We understand that many of you have busy schedules, and want to know if growing your own weed is a realistic goal for you.

The amount of time spent growing varies greatly depending on the method you use to grow, the size you let your plants get and the skill of the grower. But that doesn’t mean there isn’t a growing method that’s conducive to spending less time plant-tending.

The truth is, you can grow weed in only 20-30 minutes a week when you use the right techniques and get used to the process of growing. The following article reveals the best way we know to grow lots of potent bud while using a minimum amount of time to do so. We make this happen using a hydroponic style of growing known as Top-fed DWC (aka “bubbleponics”).

Keep in mind that this is a fairly advanced technique, and should only be attempted by intermediate-advanced growers or particularly brave newcomers.

About Nebula Haze:

Medical m arijuana has had a huge impact on my life, and I’m dedicated to showing you how easy it can be to grow your own medical-grade buds.

I have made it my mission in life to make growing information available to anyone, both new and advanced growers, while also working to get marijuana legalized for all adults.

Learn 7 tactics to harvest your weed as quickly as possible… ]]>