Learn everything you need to know about watering your cannabis plants. No more guessing or worrying! Water plays a crucial role in keeping your marijuana plant healthy. Get tips from the experts at Leafly to keep your weed plants hydrated, and learn how to flush them properly. 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 Often Do I Water Indoor Marijuana Plants?
If you’re growing marijuana in soil or another growing medium like coco coir, you will have to hand-water your plants. Watering is an important part of growing cannabis indoors, and knowing how to water your plants will save you a lot of frustration!
How often do you give your cannabis water?
Well, you will want to water your marijuana whenever the top of the soil or growing medium starts to feel dry. I like to water when the medium feel dry up to my first knuckle, or about an inch.
- Soil – Water plants when the soil feels dry up to your first knuckle (or if the pot feels light).
- Coco Coir – Aim to water plants every 1-2 days. If coco is staying wet for 3+ days, try giving less water at a time until plants get bigger and start drinking more. Don’t wait for your coco coir to dry out, but don’t water if the top inch feels “wet”. If the container feels light, it’s definitely time to water!
How to water cannabis properly (when using a well-draining potting mixture with liquid nutrients)…
In soil, wait until the topsoil feels dry about an inch deep (up to your first knuckle – just use your finger to poke a hole in the soil and see if it feels dry).
In coco coir, you want to water every 1-2 days if possible and adjust the amount of water you give accordingly. The top inch doesn’t need to completely dry out between waterings.
If you’re regularly adding nutrients in the water, give enough water each time that you get 10-20% extra runoff water drain out the bottom of your pot. This prevents a buildup in the potting mixture because otherwise, you are continuously adding more nutrients to the system.
Go back to step 1. Note: If water takes a long time to come out the bottom, or if pots take longer than 5 days to dry out before the next watering, you may actually have a problem with drainage (more info below) or need to give less water at a time. If your plants are very small compared to the container they’re in, give water more sparingly until plants get bigger.
Growing in Super Soil?
- If you’re growing in super soil or another heavily amended potting mix, you may not need to add extra nutrients to the water because your plants can get all their nutrients directly from the soil.
- Any time you’re not adding extra nutrients in the water, you want to avoid getting runoff water because it will carry away some of the nutrients in the soil.
- Watering until you get runoff is important when using liquid nutrients because it helps prevent nutrient build up, but with super soil try to give just enough water that you wet the entire medium but don’t get extra water coming out the bottom.
Some growers swear by the “lift the pot” method to decide when to water your plants (basically wait until your pot feels “light” since the plants have used up all the water). It’s up to you to decide what’s easier for you.
I usually water my cannabis with a 1-gallon water jug for small grows, or 5-gallon jugs for larger ones. Runoff water is collected in the trays and after a few minutes I suck it all up with a small wet vac .
How to Provide the Water
When I first started growing, I gave my plants water using a watering can. A watering can works great, but it’s hard to water a bunch of plants with one watering can because you have to keep filling it up.
An old-fashioned watering can will get the job done, but they typically don’t hold a lot of water at a time, which is inconvenient if you’re growing a lot of plants
I personally like using a Battery Operated Liquid Transfer Pump to water the plants. You can pump water from a bigger container to your plants. This is a 3-gallon water container from Wal-Mart, and the pump just reaches the bottom.
My grow tent is 2 feet deep and this reaches the plants in the back. However, I don’t think the tube is long enough to reach the back if your space is deeper than that.
Some growers set up elaborate drip feeds to pump water if they have a lot of plants they can’t easily reach, both homemade or pre-made.
Let us know if there’s something we missed. Growers get creative!
How to Collect Runoff Water
It’s important to keep plants on saucers or trays so you can remove the runoff water. You can collect the saucers one by one and dump them out, but that also gets inconvenient with many plants.
It’s inconvenient to empty saucers one by one if you have a bunch of plants, but you don’t want to leave plants sitting in runoff water
If you put your plant on plastic trays, and then put the trays on a slight incline by putting something small underneath in the back, it will catch all the runoff water and cause it to drain to the front. The item in the back only needs to be about half an inch thick, for example a piece of plywood. However, if you can find something more water-resistant, like plastic, that’s even better.
These 1’x2′ plastic plant trays work well if they fit your space. You can fit four of them in a 2’x4′ grow tent (this is the grow tent I use) with up to two plants each as long as your plant containers are 11″ wide or smaller at the base.
Put trays on a slight incline by placing something underneath the tray in the back. This causes all the water to come to the front for easier collection. Each of these trays has a small plastic board (which we found around the house from something else) under the back. Anything that’s about half an inch high will do the trick. These particular trays accommodate plant containers up to 11″ wide at the base.
Not sure how to remove runoff water after watering your marijuana? Wet vacuums can be a great choice, especially if you already have one in the house. I didn’t have one, so I got Bucket Head attachment which can turn any standard 5-gallon bucket into a wet vac. You can buy one online but it’s $10-15 cheaper if you get it in person at a Home Depot. Another similar option is the Power Lid, though it’s also a bit pricey.
A downside to the Bucket Head is it’s a little loud, just like most wet vacs. Luckily you only need to use it for a few minutes after watering your plants!
Removing runoff water is a great start to make sure you are watering your cannabis plants perfectly, but it’s also important to…
Make Sure Pots Have Good Drainage
It’s very important to make sure that water can drain freely from the bottom of the pot, otherwise, the plant can get waterlogged and become overwatered (causing the plant to droop).
In addition to making sure the actual container has drainage (holes on the bottom, or some other way for extra water to escape), it’s also important to make sure your growing medium drains freely. If it takes several minutes for the water to come out the bottom of your pot when you water, it means that there isn’t enough drainage in the actual growing medium (it’s too dense, so water is having a hard time getting through).
How to improve the drainage of your growing medium
- Never use dirt you find outside. Chances are it does not have the correct properties for vigorous cannabis growth.
- Mix in extra perlite to loosen the soil and allow water to drain through more easily.
- Bark or wood chips are not the best choice for growing cannabis plants, even though they’re sometimes recommended to improve drainage in soil for some types of plants. On that note, avoid using soil that contains bark or wood chips. What makes soil good or bad for growing cannabis?
- Use Smart pots – these fabric pots help get oxygen to your roots (which gives you faster growth) and this type of pot makes it harder to overwater your plants. A cannabis plant growing in a tan fabric smart pot is pictured to the right.
This is an example of great soil for growing for cannabis – rich, composted, and well-draining
Composted super soil lets you grow organic marijuana without any extra fertilizers or nutrients
Watering Too Often? Barely at All?
In the beginning of your grow, you will likely be watering your marijuana plants every couple of days. Watering every 2-3 days is optimal for a young plant. If it’s taking too long for your plant to dry out, you may need to give less water at a time until the plant is growing faster.
If you feel like you are watering your plants too often, you may need to give more water at a time. You can also move plants into a bigger pot (which holds water for longer).
If plants take longer than 3-4 days to dry, make sure your potting mixture has good drainage and consider giving less water at a time
If plants are drying out in 1 day or less, try giving more water at a time or transplanting to a bigger pot
Speaking of pot size, it is generally best to start young cannabis plants in relatively small containers (like a solo cup with a few holes cut out of the bottom for drainage), and move plants into bigger containers as they get bigger. Starting in smaller containers makes it a lot harder to overwater your plants when they’re young, and makes it easier to flush plants and/or respond to problems if they occur.
That being said, you can plant your seeds right into their final container. Just be careful not to overwater your seedlings at first if they’re in a big container as they’re not drinking much water in the beginning.
If you started your plants in a solo cup, I’d recommend moving to a bigger pot once the plant is a week or two old, as soon as the leaves reach the edges of the solo cup.
10-20% Extra Runoff Every Time You Water (if you’re providing nutrients in the water)
Every time you water your plants, make sure that you provide enough water to get about 10-20% extra run-off out the bottom of the container, especially if you’re feeding additional nutrients in the water.
Sometimes soil and soilless growing mediums like coco coir start to collect natural salts from fertilizers that never get washed out.
These built-up salts can eventually cause nutrient problems, pH problems, and nutrient lock-out if they’re not removed on a regular basis.
Making sure you keep adding water until you get run-off is also a great way to make sure that your plants are draining properly.
Plus, this practice will immediately alert you to any drainage problems, (as mentioned earlier, cannabis likes well-draining soil) because you’ll be able to notice if the water takes a long time to come out the bottom, or doesn’t come out at all.
Different Nutrients for Different Stages of Life
First, make sure you’re using proper cannabis nutrients for your growing medium. They should be formulated for a plant like tomatoes, and they should have a different feeding schedule for the Vegetative (Grow) and Flowering (Bloom) stage.
If using nutrients on a regular basis by adding them to your water, it’s generally a good idea to give your cannabis plants nutrients every watering. This ensures the amount of nutrients in the plant root zone is kept relatively stable. If you notice the tips of leaves getting burnt from nutrient burn, it may mean you need to lower your overall strength of nutrients. Most nutrient recommendations on the side of the bottle are too strong for cannabis plants, and should be cut in half unless plants appear pale or lime green (which means they want higher levels of nutrients overall).
If Growing in Composted or Amended Soil, Give Just Enough Water That the Soil is Wet All the Way Through
When growing in composted and amended soil, the soil itself is made to slowly provide nutrients to your plant throughout its life. However, if you’re regularly watering until you get a significant amount of runoff, you’ll also be washing away some of your nutrients.
This is good when the plant is getting the nutrients directly in the water, to avoid unwanted buildup in the soil, but try to avoid a lot of extra runoff if you want your nutrients in the container to last until harvest.
Therefore, when growing in amended soil you should only water until you get just a drop or two of water runoff out the bottom. You want to ensure you gave enough water to reach the bottom of the pot without letting a significant amount of water run out the bottom.
Proper watering practices will greatly help reduce the amount of salt buildup and prevent nutrition problems from occurring.
If your cannabis plants shows signs of drooping, often the plant is getting too much or too little water, but not always. Drooping can be caused by….
- Too much water at a time, or giving water too often
- Not enough water at a time, or giving water too infrequently
- Drooping can also occur in hot conditions, or when it’s very humid or dry because the plant isn’t able to move water properly through the plant.
- Plants sometimes get droopy if they are given a lot of water after being allowed to dry out for too long, due to the stress of the water pressure quickly changing at the roots.
- Drooping is almost always associated with something going on at the roots, but plants also tend to put their leaves down a bit right before the lights go off, as if they’re preparing to “sleep” for the night. That can sometimes be mistaken as drooping when its actually part of the plant’s natural rhythm.
In order to prevent over or under-watering, make sure you water thoroughly every time (don’t just water a tiny spot in the middle of the pot unless you plant is very small for the container). You should be getting 10-20% extra runoff water every time if you’re adding nutrients in the water. In soil, wait to water again until the top inch of the growing medium feels dry, up to your first knuckle or so. In coco coir, aim to water the plants every 1-3 days if possible, and don’t let the top completely dry out between waterings.
Underwatered Marijuana Plants
- Wilting is the first sign of underwaterd marijuana plants
- Leaves are limp and lifeless, they may seem dry or even “crispy”
- Will eventually lead to plant death if not corrected
Overwatered Marijuana Plants
- Drooping / Curling is the first sign of overwaterd marijuana plants
- Leaves are firm and curled down all the way from the stem to the leaf
- Will eventually lead to leaf yellowing and other signs of nutrient problems if not corrected
If your plant is experiencing “the claw” and not just normal drooping (like the ends of leaves are just pointing down like talons, then you may actually have a nitrogen toxicity (too much nitrogen).
Nitrogen Toxicity (“The Claw,” tips bent down, dark leaves)
Learn more about Nitrogen Toxicity
How to water and flush marijuana plants
Like all plants, cannabis requires water in order to perform its basic functions. Water helps plants absorb nutrients from the soil and then moves up the plant and into the leaves, and without it, the plant can’t survive. But giving a marijuana plant the proper amount of water may be more difficult than you think.
There isn’t an exact science for watering a weed plant. You can’t observe the roots in most cases to see if they need water. Also, a plant is constantly growing and the climate it’s in will fluctuate, so the amount of water it needs constantly changes.
Here are some tried-and-true tips to keep your weed plants healthy and properly hydrated.
How often should you water marijuana plants?
A common mistake first-time growers make is to overwater marijuana plants. A cycle of wet and dry is healthy and necessary for the roots of a plant to grow out and reach deeper into the soil.
Additionally, roots pull in oxygen as soil dries and when soil is too wet, the plant can’t pull in oxygen efficiently and essentially can’t breathe.
Below are general estimates and are meant to give growers a rough sense of frequency of waterings; if a plant needs water and it falls outside of these ranges, water it.
|Plant stage||Water every # of days|
How to tell if a cannabis plant needs watering
The best ways to tell if a weed plant needs water is to:
- Stick a finger 1-2 inches into the soil—if it’s wet, hold off; if it’s dry, it’s time to water.
- You can also pick up a pot and feel its weight to determine if it needs water. This will take some experience—be sure to lift up your pots after watering to get a feel for how heavy they are when full of water. This will also give you a sense of what a light, dry, plant feels like.
An under-watered marijuana plant looks droopy and weak, with yellow or brown leaves; there is no strength in the leaves and they look lifeless.
Leaves of an overwatered plant look slightly similar in that they droop, except the leaves will be dark green and the leaf tips will be curled.
Note how often you water plants and write it down in a log. Get your marijuana plants on a watering schedule—as they grow out of the seedling stage, watering every two to three days is ideal.
Keep in mind that as plants get bigger, they will need more water and need to be watered more frequently.
When growing weed outdoors, you’ll need to water more often as the weather gets hotter and less often as it cools.
When you find the sweet spot between too wet and too dry, your plants will flourish.
How much should you water marijuana plants?
The amount of water your marijuana plants need depends on a few factors:
- Size of plant
- Outside temperature
- Overall health
- Stage of growth
You want to water a plant enough to soak all the soil in the pot. Water should pool up on the surface of the soil when you’re watering, and come out the drainage holes in the bottom of the pot after a couple seconds. If water sits on the surface of the soil, that means it’s too wet and doesn’t need more water.
If a weed plant is very dry, water will run straight through the soil and pot and quickly come out the drainage holes. If this happens, water the plant a little bit and then come back to it after 15-20 minutes and water it again, and maybe even a third time. This allows the soil to slowly absorb water until all of it is thoroughly wet.
Roots are constantly on the hunt for water as they grow and stretch out. As a plant gets bigger, so should the watering radius—the area around the stalk of the plant that you water. Doing this will help guide roots to the edges of the pot as they seek available nutrients in soil.
Watering too far away from the roots can create standing water, which can lead to root rot, mold, and pest issues.
Is your container the right size?
To properly water a cannabis plant, it needs to be in the correct size container, or a big enough hole if it’s in the ground. If a pot is too big, the plant’s roots can’t drink water where they don’t reach. If the roots aren’t absorbing water, water will sit in soil and take a long time to evaporate, which can promote root rot and unwanted insects and fungus.
Conversely, if a container is too small, the roots won’t be able to stretch out, which can stunt the growth of a plant. Less soil also meant you’ll need to water the plant all the time, which will add labor.
Ideally, cannabis plants should start in a small pot and progress to bigger and bigger pots as they outgrow each container. For example, you can start a seedling or clone in a 4″ or 1-gallon pot, then move on to a 2-gallon, 5-gallon, 10-gallon, and so on.
Plants are ready to transplant when a healthy root structure encompasses most of the soil and the roots aren’t bound. When transplanting, take time to look at the quality of the roots: Bright white roots with a strong, thick structure is a sign plants are getting watered correctly.
What is flushing?
Flushing is an important part of the marijuana growing process, when you stop giving a marijuana plant nutrients and give it straight water. This is done to flush out nutrients that may have built up in a plant during its life.
Flushing is done for about a week before harvest, at the end of a plant’s flowering stage when buds are almost ready to cut down.
A flush can also be done to clear plants of nutrients if they have a nutrient imbalance, such as nutrient lockout, when your plants are overloaded with nutrients and unable to absorb new ones.
How to flush weed plants
Flushing marijuana plants before harvest
The final flush should occur for a week or so before you cut down weed plants for harvesting. Water your plants with the same amount as you normally would, but only with water. This will force the plant to use the nutrients stored within it—if its nutrient reserves are not used or broken down, it could affect the quality of your harvested buds.
By looking at the trichomes on marijuana plants, you’ll be able to tell when the plants are ready for a flush—begin when they start turning milky.
Different growing mediums require different flushing timeframes before harvest:
- Soil: 7-10 days
- Rockwool and coco: 7 days
- Hydroponics: 5-7 days
If growing in amended organic soil, it is not recommended to flush plants. This is because the soil already holds all the nutrients the plant needs to thrive, and by flooding the soil you can wash away and damage the complex ecosystem that you’ve worked hard to develop.
When to stop watering before harvest
Water your marijuana plants as normal when in the flushing phase—don’t let them get too dry or too wet. Make sure not to harvest dry or wilting weed plants—they should be nice and healthy when you cut them down.
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!
The germination of cannabis seeds is illegal in most countries. Amsterdam Genetics cannabis seeds are exclusively sold as collectable souvenirs to customers living in countries where the cultivation of cannabis is illegal. All information on this website is intended for educational purposes only and is not meant to incentivize people to engage in illegal activities.