How to Waterweed Plants – Tips to Avoid Overwatering and Underwatering

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How to tell if a cannabis plant needs watering?

While it’d be great to tell if your plants need to be watered by looking at them, the truth is that the safest way to tell whether or not it’s time for your plant to get watered is by touch. Stick your finger about an inch or two into the soil under the plant.

If the soil is dry, it’s time for you to water your cannabis plant.

How often should you water marijuana plants?

Of course, most people aren’t going to check every one of their plants every time they want to water them. Though there’s not an exact number here, there are some rough numbers that you can follow depending on the life stage in which your plant finds itself.

If your plant is just germinating, you’ll water it once every four to seven days. If it is a seedling, you may water it ever so slightly more often – twice a week at most.

By the time the plant is vegetative, you’ll water it once every two to four days. Once the plant is flowering, you’ll look to water it at least once every three days.

How To Water Your Cannabis Plants

Watering plants is fairly easy. You’ll simply pour water on the plants and watch the soil.

If the water pools briefly on the top and drains out through the bottom of the pot, you’ve done a good job. If the water runs through without pooling, the plant is underwatered.

If the water pools without draining, you’ve overwatered the plant.

The Importance Of pH When Watering Plants

It’s vital that you monitor the pH of the water in which you grow your plants. Ideally, a marijuana plant is going to be watered at around a 6-7 on the pH scale, which is quite close to neutral.

This is the ideal level for nutrient uptake and thus will allow your plant to flourish as best it can.

Don’t Leave Your Plants Sitting In Runoff

By the way, don’t leave your plants sitting in the runoff water from your last round of watering. While you might think of this as a clever way to ensure that your plant gets water as long as it is needed, the truth is that this ignores how plants of any sort work.

If you’ve got runoff in which your plant can sit, you’ve got a situation in which your plant is actually dealing with the impacts of being overwatered. Your goal should be to move your plants if they’re in standing water so they can actually grow properly.

What is flushing?

Flushing is one of those parts of the marijuana growth process that’s often ignored but that’s incredibly important. Flushing is the stage at which you stop giving your plants nutrients and start just using water, which can flush away excess nutrients and prevent some nasty health problems in most plants.

It should be your goal not just to flush at the right time, but to know how to flush your plants properly.

How to flush weed plants

Flushing is a wonderfully straightforward process. Go ahead and water your plants when you would usually water them, leaving out any of the bits where you add nutrients to the soil or plant.

Once you’re done, take a fifteen-minute break and come back to water the plants again. This should be sufficient to wash out any nutrients that are left behind.

Flushing marijuana plants before harvest

It’s always a good idea to flush before you harvest. Flushing doesn’t just get rid of excess nutrients in the soil; instead, it helps to force the plant to make use of all the nutrients that it already has.

How to tell if a cannabis plant needs watering?

“The person trimming leaves of medical marijuana plant close-up. Source: Author:”

This will help to prevent any issues with nutrient imbalances and allow you a better chance to make it through the final stage of growth without problems. Follow the same flushing timeline as above, generally at around five to ten days before you plan on harvesting depending on your soil type.

When to stop watering before harvest

One thing to remember is that you actually need to keep watering your plants right up until harvest. Keep watering them as you normally would, as a dry or wilting plant is not a plant that you want to harvest.

As odd as it might sound, you really want to keep your plant’s routine fairly normal before it is time to harvest.

Flushing marijuana plants for nutrient imbalance or lockout

If your plant is dealing with a nutrient imbalance or lockout, you’ll want to flush out the soil so that you can start from scratch. This method of flushing is honestly the same as that mentioned above, but it does require paying very careful attention to your water.

If you are flushing in soil, you’ll want to use a pH level of between six and six-point eight. If you’re flushing a plant grown in aeroponics, you’ll flush at a pH of between five and a half and six and a half.

How to source the best water for marijuana plants

As you start looking into watering your plants, you’re going to have to start paying attention to the water you use. Remember, growing marijuana can be a very delicate process and you’re probably not just going to use water straight from a hose.

It’s up to you to make sure that you pick the right kind of watering option that will help you to get the best harvest and eventually to get the kind of yield that you need for your future goals.

Know Your pH and PPM

You need to know the pH level of any water that you use to grow cannabis. As a rule, you’re looking at something as close to neutral as possible – a seven is ideal here, but try to err on the side of going lower than going higher.

PPM, or parts per million, of contaminants, is also important to track. Water can be full of all kinds of chemicals that can inhibit the growth of your plants, so the fewer parts per million of those substances in your water, the better.

Where to source water

There are a handful of places to source your water for your grow operation. All of them have different pros and cons, so it’s up to you as a grower to stop and think about where you can source the water that best fits your needs.

Unfiltered tap water

The old staple for watering cannabis was always unfiltered tap water. It tends to be the go-to because it is cheap, easy to secure, and seemingly always available no matter where you are.

We explain how to waterweed plants - tips to avoid overwatering and underwatering

“Young Green Leaf Cannabis Indica. Source: Author: arsfolk”

The downside, though, is that most tap water is treated for human consumption – something that’s great for humans, but not so good for plants. As such, you may have to do work to decontaminate your water before you use it on your plants.

Water collection systems

A good water collection system allows you to collect rainwater or other types of natural water for your plants. Easy to scale and great for the environment, it’s hard to find a source of water that is cheaper than mother nature.

The downside here, though, is that you’re going to have to figure out how to both filter and store your water. The answers to those questions, unfortunately, generally require spending a fair bit of money.

Bottled water

Yes, you could choose to use bottled water to grow your plants. It’s pure, it’s relatively cheap, and it’s safe for your plants.

Plastic is also awful for the environment and the fact that you’re going to have to lug around and store more water than you might expect can also end up being very labor-intensive.

Reverse osmosis (RO) systems

If you’re looking at high-tech solutions, you can try an RO system. These water systems totally clean your water, creating a perfect source of hydration for your plants.

They’re honestly the best solution for those with deep pockets, but those who have a somewhat smaller budget or who aren’t operating at scale are going to want to look elsewhere for a more monetarily feasible solution.

How To Water Cannabis Plants When You’re Away

So, what do you do about watering your plants while you’re gone? There are a whole host of possibilities here, ranging from just timing your trips based on your watering schedule, taking the time to get a trusted friend, co-worker, or employee to do the watering for you, or even using an automated system like a sprinkler system to do the job.

What’s important, though, is that you stick as close to your usual watering schedule as possible. Failure to do so can lead to a ruined crop.


Don’t overlook the importance of watering your crop. Pay attention not just to when to water your cannabis, but also to how much you should be watering your plants and with what kind of water.

Once you can get your methods and routines down, you can cross off one very important item on your list of ways to keep your plants healthy and productive.