Crops need love too! Cannabis plants thrive when provided with the right amount of water and nutrients. Watering cannabis plants may seem simple, but there is an art to it. Learn how to avoid the usual pitfalls and make the most out of any grow!
How to water a cannabis plant
Cannabis is generally a resilient plant, and most strains can tolerate mistakes with feeding and watering to some extent. However, consistently delivering water and nutrients in the wrong concentrations or quantities can cause deep-rooted problems that can prove detrimental—or even fatal—to your crop.
Cannabis plants need abundant water, particularly in the flowering stage. As a general rule, plants should never be deprived of water for too long at any stage of their life cycle, as this can severely slow or even halt growth entirely. As well as this, depriving plants of water deprives them of nutrients, which not only slows growth but can lead to deficiencies.
Moderation is key
However, over-watering is a mistake many new growers make. Over-watering can lead to pythium (root rot), botrytis (grey mould) and powdery mildew, as well as causing nutrient toxicity and anaerobic (oxygenless) soil conditions in extreme cases. These issues can be disastrous, and are often extremely difficult for newbies to correct.
Most growers agree that soil should be allowed to dry out slightly between feeds—this lessens the risk of rot, mould and nutrient burn, and may also encourage the roots to grow denser. However, plants should always be watered before the roots start to dry out.
Finding the right balance is crucial, and it varies according to the strain (tropical sativas may be remarkably thirsty, while many indica strains abhor damp) and the size and growth stage of the plant—as well as other factors such as choice of medium.
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When should cannabis plants be watered?
There is some controversy over the best time of day to water cannabis plants. Most growers believe that cannabis should be watered at night time, but some argue that they should be watered earlier in the day.
Those that believe cannabis plants should be watered at night argue that in a natural environment, precipitation does not fall when the sun is shining, due to cloud cover. Many also state that if water droplets resting on the leaves are exposed to heat and bright light, they may act as “magnifying glasses” and burn the leaves.
It appears that this is just a myth, although leaf burn can occur through prolonged contact with some fertilisers. In any case, possible issues can be avoided altogether if care is taken to simply direct the water towards the soil and not the leaves!
On the other hand, watering earlier in the daytime allows the plant to utilise the available nutrients more effectively, as many of the fundamental processes of plant growth occur in sunlight. Leaving soil damp throughout the cooler hours of night can promote mould growth.
If growing outdoors, watering in the morning rather than the warmer afternoon appears to be optimal, as the rate of evaporation is slower. If growing indoors, watering at around the time lights are switched on may be preferable—while temperatures rise quickly with “hot” lights such as HPS, it usually takes some time for them to peak.
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How often should cannabis plants be watered?
At first, young plants will require small amounts of water at frequent intervals—up to twice per day if room temperatures are high and relative humidity is low. As they mature, they may be fed less frequently with greater quantities. Typically, large flowering plants must be fed at least once every 2-3 days.
The correct time to water plants should become apparent upon testing the moisture level of the growing medium. It should feel dry on top, but still somewhat damp below the surface. If it remains dry to the touch at depths of more than 5cm or so, plants are probably too dry.
This may all vary widely according to the drainage properties of the medium. For example, coco typically requires daily watering at first, then twice-daily as the plants increase in size; this is due to the fact that it retains water extremely well, so giving too much at once can saturate the medium and reduce airflow.
With experience, a visual check or simply testing the weight of the container will aid in determining when to feed, as a dry container obviously weighs substantially less than one full of water.
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A step-by-step guide to watering cannabis plants
First, prepare your equipment. You will need a source of water, a pH meter, pH down (this could be any strong acid), your chosen nutrients, and a watering can, hose or similar.
Water should be around room temperature—hot or cold water can shock and stress plants severely and sometimes irreparably. Most agree that water should be left to stand for 24 hours before use as this allows pH to be more accurately determined.
pH should be between 6.0-6.5 if growing in soil; if growing in soilless medium this value may be somewhat lower (coco prefers the 5.5-6.0 range). Use pH down to reduce pH if necessary, making sure to mix well. Incorrect pH can result in nutrient burn and various deficiencies, as roots are unable to process nutrients as effectively.
Add nutrients according to the manufacturer’s instructions, and mix thoroughly. Nutrient concentrations may be adjusted according to the strain and the stage of growth of the plant—such as when plants are young, or just after being transplanted.
Using a watering can, hose or similar, water the plants until runoff is visible in the trays beneath the pots. Many growers aim for around 10-20% of total water draining off, as this is believed to prevent nutrient build-up—but this is disputed.
Nutrient build-up occurs due to oversupply of nutrients (or reduced uptake by the roots due to overwatering or pH issues), and is fixable by flushing with pure water and not by adding more nutrient solution.
This basic guide should give novice growers all they need to successfully water and feed cannabis plants. However, adjustments to the basic principles may need to be made according to local climate, choice of strain, type of medium, and several other factors.
Laws and regulations regarding cannabis cultivation differ from country to country. Sensi Seeds therefore strongly advises you to check your local laws and regulations. Do not act in conflict with the law.
Watering Cannabis Plants: How, When, And How Much?
Watering cannabis plants doesn’t sound like a big deal; any idiot can do that, right? Well, wrong, actually. There’s a bit more technique involved in watering weed than simply sloshing some H2O at your pots every once in a while. At least, that’s not going to do if you’re aiming for strong, healthy plants with big, beautiful buds. Watering cannabis plants is all about finding that sweet spot between giving too much water, or giving too little instead. If you approach watering marijuana the wrong way, you may cause nutrient shortages, or your plants could get sick. To prevent that from happening, this blog gives you a clear guide to wearing cannabis plants, including how much to give, when to do it, and in what way.
The Art Of Watering Cannabis Plants
Watering cannabis plants may not be the first challenge that comes to mind when ordering marijuana seeds to grow. Most people think they’ll be fine as long as you just keep their feet wet. It’s not quite that simple, though. Growers looking for strong, healthy plants should be careful about how much water they give; when they do it, and how they keep them watered. Sure, talking about the art of watering weed may sound awfully zen, but there is an art to it nonetheless. If you just keep the following guidelines to heart, it can really up your growing game.
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Why Weed Needs Water
Without water, there would be no weed plants – it’s that simple. But what do cannabis plants actually use all that water for? It seems so obvious, but here are six reasons for watering your marjuana grow – bet you didn’t know all six of them…
1) Cannabis plants are almost 90% water. They need water to keep their cells firm so the plant remains steady and upright while retaining its structure.
2) Plants need water for photosynthesis. That means without water, plants would have no energy to store, or to use for growing and flowering.
3) Seeds won’t germinate without water. As you can see, even the very first step of any grow is 100% dependent on water.
4) Water is necessary for transporting and absorbing nutrients. Although a plant’s roots absorb nutrients from the soil, they can only do so if nutrients are dissolved in water.
5) Plants use water for ‘transpiration’ so they can keep their temperature stable when it gets (too) hot.
6) Soil life needs water, and without the right life forms in the ground, many vital processes would stop working.
Right. Now that we know why we need to water our cannabis plants, let’s proceed to the best water management techniques.
The Main Danger: Too Much Of A Good Thing
Everyone knows that water is essential for a plant’s survival. What many people don’t know, however, is that too much water can harm or even kill a plant. It’s all about having too much of a good thing, really. Most rookie growers tend to give too much water to their plants rather than letting them dry out. That is why you should always be sparing in watering cannabis plants, as you’re more likely to cause problems by overwatering than by dehydrating them. In fact, for very young plants, even the splash that your average watering can produces can be harmful. There’s your first lesson on watering cannabis plants already, then: don’t damage shoots and roots by using a watering can for seedlings and young plants. The best way to go with the little ladies is to use a spray nozzle instead.
Spraying water is better for young plants.
The next tip is more of a where than a how, really. Always start watering cannabis near the stem of the plant, and work your way towards the edge of the pot from there. This encourages the plants to extend its roots outwards to all sides. A more elaborate root system equals a stronger plant with better resilience to outward influences. This applies both to plants raised in pots and to marijuana grows in open soil.
Learning When To Water Cannabis Plants
Too much or too little water can be equally bad for marijuana plants. How much water any individual plant needs depends on several factors, including the stage of its life cycle, soil type, and temperature. As a basic principle, keep in mind that cannabis plants have to be watered every two to three days. The exact watering frequency is determined by the variables listed below.
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Indoor Or Outdoor Grow?
Let’s start with an obvious one: watering outdoor grows is very different from watering cannabis indoors. Inside, growers provide every last drop of water themselves, while outdoor growers have to take drought and rainfall into account. Although this is part of the charm of growing weed in a natural environment, it does add some complications to the process (or at least, different complications). The following tips all apply to outdoor grows, with one crucial addition. Always keep close track of how much rain falls, and when, using a simple rain gauge or similar technique.
While applying the tips from this blog, always take into account what nature has already provided. In dry, hot weather, water evaporates from the plant and from the soil at increased rate. That means you’ll have to water more often. Rainy days can make watering almost unnecessary. In fact, if it keeps pouring for days on end, finding your plants some shelter can be a good idea. Obviously, that’s not going to work for plants out in the open soil, but this problem is partly offset by better drainage than your average flower pot.
Indoor grows grant much more control over the grow environment. Temperature and air humidity can be kept stable, allowing growers to curb evaporation rates. However, watering cannabis indoors poses its own set of challenges. If you forget to water your plants, there is no natural backup rainfall to save them. On the other hand, you don’t want to overwater them either. That is why indoor growers usually work by cycling from wet to dry, letting their grow medium dry out almost entirely before adding new water.
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Indoor growers differ in the level of automation they use. Some grow systems are fully automatic, watering at given times with all the nutrients added to the liquid. Others just use a watering can instead, and then there are many grow setups that are somewhere between these ends of the spectrum. Generally speaking, the less tech and automation you use, the more you should use the guidelines in this blog for careful watering of your cannabis grow.
Ebb And Flow
When growing weed indoors, watering can be arranged by using an ebb and flow setup. This involves temporarily submerging the roots of the plant, allowing them to absorb water rapidly. Usually, nutrients are already added to the water in advance, and the water is flushed out afterwards. That calls for regular refreshment of the water reservoir to deny fungi and bacteria a foothold.
Grow Medium And Watering Cannabis Plants
The soil type in which you decide to grow your cannabis affects the preferred frequency of watering. Different grow mediums have different properties. Clay, for instance, has very good water retention, while sand has excellent drainage properties. Cannabis prefers loose soil that is capable of draining away excess moisture fast. That’s why you should remember to drill a few holes in the bottom of your pots. If you don’t, water will collect in the lower soil strata, which will get you in trouble eventually.
No matter whether you grow indoors or out, the following summary lists some of the main benefits and drawbacks of various grow mediums:
(Potting) Soil: Depending on composition, soil or potting soil provides growers with rich organic soil life, good drainage, and adequate retention capacity (ability to trap moisture). Many soil types offer their own supply of nutrients, reducing the need to add fertilizer. Natural soil also has high buffering capacity, which adds stability to the grow and limits the impact of mistakes.
Perlite/ Clay Pellets: Growers often add perlite or clay pellets to their grow medium to amp up water retention capacity. This extends the wet-to-dry cycle, reducing the need to water often. Clay pellets can also help keep evaporation in check in hot weather.
Coco Fibre/ Coco Peat: Coco fibre can be used as a grow medium instead of potting soil. It is highly effective at trapping water, thus prolonging the wet-to-dry cycle. That means you should pay extra attention to remaining moisture, because the risk of overwatering is bigger
Rock wool: Rock wool is an alternative to soil used almost exclusively indoors. This fibrous material has excellent water retention power as well as good drainage capacity, which generally decreases the required watering frequency, too.
Hydroponics: Growing cannabis using hydroponics is an altogether different affair. This method involves growing plants directly in water, without using soil or any grow medium whatsoever. The water holds all the necessary nutrients if you do it right. As you’ll understand, the guidelines in this blog do not apply to hydroponic grows. You can read more about hydro grows in our dedicated hydroponics blog.
Especially when growing weed indoors, water quality makes all the difference. This is where individual approaches differ considerably, though, mainly because many weed growers only have access to regular tap water. Of course, tap water quality varies wildly between regions and countries, but generally speaking, cannabis plants can handle whatever spills from the tap. Growers living in hard water areas (where groundwater and tap water contain high levels of calcium) may want to purify their cannabis water supply to prevent mineral deposits, though. Weed can suffer from calcium and other mineral deposits. High-tech indoor growers should note that mineral deposits can damage automatic irrigation systems too.
Ideally, the purest and – according to many – best water quality comes with purified reverse osmosis (RO) water. This can be tricky to come by in large quantities, however, so we are just going to leave the suggestion here and repeat that generally speaking, clear tap or rain barrel water will do nicely.
Outdoor growers can also install a rain barrel for a water reservoir. This takes some planning ahead, but on the plus side, it can seriously cut water expenditure and ecological footprints, as well as supporting any attempt to grow weed organically. Incidentally, building your own filter for water barrels is not as hard as it may seem.
Clean, fresh water is always a good idea; however, pH values and nutrient contents are equally essential.
The Right pH For Watering Cannabis Plants
Cannabis plants can make the best use of water that is slightly acidic, at pH values (representing acidity) of about 6.5. You can use a pH meter to gauge whether your water is too acidic, or too alkaline instead. If that happens, the roots become unable to absorb the nutrients from the grow medium. That will slow down growth and could eventually be fatal. Here too, outdoor grows in open oil are less vulnerable to acidity fluctuations; indoor growers should pay extra attention to pH.
pH meters are useful tools for any grower.
Adding Nutrients, Yes Or No?
Then there is the question of which nutrients, if any, to add to the water you’re using. There are as many preferences as there are growers when it comes to nutes, but being cautious is always a good idea. Nutrient deficiency harms plant development over time. Overfeeding can cause ‘nutrient burn’, which will also prove fatal in the long run. Here too, the grow medium makes a big difference. In potting soil, for instance, many of the important nutrients are already naturally present, whereas rock wool offers no nutrition at all. As mentioned earlier, many indoor growers automatically use premixed vats of water and nutrients, with different composition for growth and flowering stages, specifically attuned to what the plants need at any given time.
The Life Cycle Stage Of Your Plants
Young plants and seedling require less water than larger, more mature plants. Generally speaking, the bigger a plant gets, the more water it needs. Yet even though nutrient requirements can change as cannabis passes from growth to flowering stage, the demand for water tends to rise stably with plant size irrespective of these stages.
Flushing Before The Harvest
Growers also use water to flush their plants before harvesting. By giving only pure, nutrient-free water in the lasts two weeks before harvest time, the plant flushes out any leftover nutrients, for a harvest that is as pure as can be.
Temperature And Light
Light and temperature also co-determine your cannabis watering regime. Generally speaking, your plants will grow more slowly in cool conditions than in warm weather. That is why a rapid-growing plant standing in the full sunshine will need more water and nutrients than a grow in colder conditions, all other things being equal.
How Much Water Does A Cannabis Plant Need?
So how much water should you give to one pant? As a rule of thumb, watering up to 25-30% of the total pot volume (the flower pot, that is) should do the trick. That gives the plant enough water to absorb all the nutrients it needs, without soaking the soil to the point where problems arise. Still, even if you know how much water to give, you’ll need to know when to water your plants for successful growing.
When Is It Time To Water Cannabis Plants?
To some extent, growing marijuana is always a matter of intuition. Good growers, however, will keep a close watch on their plants to detect just when they need a splash of fresh water to drink. For outdoor growers, the advice is not to water plants during the hot hours of the day, as the sun can easily burn the leaves at high noon. Wait until the sun starts to set, or get up early and water your plants before the sunlight hits them.
For indoor growers, the best course of action is determining their own wet-to-dry cycles. Do keep in mind, however, that plants will finish their water rations faster as they grow bigger, or if temperatures rise for instance. Indoors as well as out, paying constant attention to water conditions remains crucial.
Whether you grow inside or out, though, you can use the following simple checks to quickly determine the moisture balance of your plants:
Fingers In The Dirt
A very simple method of finding out whether your plants are thirsty is simply to stick your finger in the soil, down to about 5cm depth. You’ll feel whether the top soil stratum has dried out easy enough. Even though you won’t get all the way to the middle of the pot in this way, you will have a rough indication of whether it’s time for water yet. In normal conditions, the top 5cm of the soil will dry out in two or three days, so you’ll know when it’s time to get your hose or watering can ready.
Another method to check whether the soil is dry is to weigh your pots. Put your pots on a scale while the soil is dry. Now, water the plants and weigh again. Regular weight checks are a good indication of when it’s time for watering.
How To Recognize Water Issues
Now that you know how and why to water cannabis plants, we round up with a few water issue symptoms. That will help you detect moisture management problems early on. There is a catch, however: some of these symptoms can signal water deficiencies as well as surpluses. So if you spot the signs of water issues, always check whether your grow medium is too dry or too damp (once again using your fingers). That way, you’re making sure you don’t pick the wrong solution and kill of your grow instead of saving it!
Limp Leaves: Not Enough Or Too Much Water
Dehydrated plants lack so much moisture inside their cells that they grow limp. Be sure to check whether the soil is dry, though. This is important, because plants can go limp after receiving too much water, too. Thirsty plants will display fragile, softened leaf structures, though, whereas drowning plants have dark green, curling leaves.
If the soil turns out to be dry, water your plant right away and watch the leaves pop back up. Don’t wait too long; weed can handle a bit of a dry spell, but regular droughts will make it difficult for them to bounce back up.
Leaves Turning Yellow Or Brown: Nutrients, Water, And Balance
If your plants are chronically dehydrated, you will notice the signs in their discoloured leaves. They may turn yellow or brown on the edges, or the leaf can lose colour altogether. What actually happens is that your cannabis grow is unable to absorb sufficient nutrients, which will retard growth and prove fatal if left unchecked.
Don’t jump to conclusions, however, as yellow leaves can signal other problems than water shortages as well. Too much water can cause discolouration too, so check your grow medium before you intervene. Moreover, too much or too little nutrition can produce similar symptoms, as can light stress. That’s why you should always pinpoint the actual cause of leaf discolouration before you act.
If the leaves of your weed plants appear swollen, similar to basil leaves for example, you are probably giving them too much water. In this case, you’re fairly certain to tackle the issue by cutting back on your watering schedule. Do make sure your drainage is in order, though, as blockages can cause water to accumulate at the bottom of the pots.
Muddy Or Bone-Dry Soil
If the soil in your pots keeps looking like mud or damp clay, you are either messing up your drainage, or you are giving too much water. Add some clay pellets or similar material to your medium to improve drainage capacity. Also make sure the drainage holes at the bottom of the pot are unobstructed. A bit of gardening mesh or some pottery shards at the bottom of the pots can help prevent them clogging up.
If the top stratum of your soil resembles a patch of the Sahara Desert, chances are you’re working with dry dirt. Try to increase the water supply, but be gentle about it or you may end up drowning your plants instead.
Conclusion: Watering Cannabis Plants, Done Right
Watering cannabis plants is not as simple as you may have thought at first, then. No matter how tricky, though, it is still one of the most important parts of growing weed. In fact, it is nearly as crucial as picking the best cannabis seeds to work with. If you want to give your crop the best shot at making it from germination to harvest, be sure to water them with proper care and attention. In your expert hands, they are bound to flourish and yield the harvest you were hoping for. Meanwhile, be sure to check out our other grow blogs, because the right knowledge can help any grower get more joy and better results from every single grow!
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