One of the most common questions we receive from cannabis growers is: How do I water my plants?
Though it might sound like a simple question, water is a critical input for cannabis, and there is a surprising amount of debate among growers about the ‘right’ way to get your plants the hydration they need. From different water sources and prep methods, to when and how much your plants need, many beginner growers struggle with water worries. Never fear! We're here to help.
What Kind of Water to Use
Reverse osmosis (RO) water, well water, distilled water, city water, rainwater: you might not have thought about how many kinds of water there are before you started growing. One of the great grower debates surrounds what kind of water you should use. The best answer (and maybe a little controversially) is to go with what works best for you!
RO and distilled water are the purest water sources you can use for growing cannabis, because there are no unknown compounds or nutrients in your water supply, just pure H₂O. This allows you to know with complete accuracy what inputs are going into your grows and limits the risk of unknown variables. However, RO water hookups or water distilling systems can be expensive to install and maintain, especially for small-scale growers. Many large-scale growers swear by it, especially when the alternative option includes purchasing bulk quantities of water solely for growing. Keep in mind that highly filtered water may still need to be pH adjusted and amended with additional trace and micronutrients such as calcium, iron, and magnesium, which are usually available in your water supply.
If you are growing with water direct from your typical drinking water source, it is a good idea to perform a water test to see what kinds of components are present in your water. Salt content, pH, city additives (chlorine, chloramine, etc.), and nutrient content, can all impact your plant development if they’re not taken into consideration. A water test can tell you everything you would need to know about whether water treatment is necessary.
When growing in a compost-based supersoil like IndiCanja®, it is not as necessary to monitor pH of your incoming water supply due to the humate-rich organic matter, and robust microbial activity, which work in tandem to buffer against rapid pH changes in the soil. There may still be some level of pH adjustment necessary, especially if your water supply naturally skews towards the alkaline side of the pH scale, but soils that are rich in microbes and organic matter are not susceptible to rapid changes in pH that can be harmful to plant development.
How Much Water to Use
Although cannabis plants are well known for being somewhat fibrous, they’re actually about 85-90% water, meaning that getting enough water is critical for plant health and function. However, overwatering plants is an incredibly common issue that can cause a myriad of health issues.
The amount of water your plants need will be largely determined by environmental factors, and the specific needs of your plants. Things like temperature, lighting, humidity, pot size, growing medium, and life cycle stage, can all determine how much water your cannabis needs to thrive. With so many variables, there isn’t a perfect hydration plan to fit every grower’s needs. However, there are some general guidelines you can use to know how much water to give your plants, and how it should be applied.
When you water your plants, you want to water deeply and infrequently. This allows your soil to partially dry out between waterings. It is better for your plants to be slightly underwatered rather than overwatered, so err on the side of keeping your plants a little dry.
Saturate all the soil in your pot evenly. Plant roots can sense moisture in the soil and will naturally gravitate towards areas where water is available. When you only water at the base of the plant’s stem, your plants won’t extend their root system beyond the column where water is being applied. This can lead to root binding and soil compaction.
In the early stages of growth, you will want to use a mister or a gentle stream of water to avoid disturbing roots and plant development. Once seedlings are a little more established, you can drench the soil more deeply. You should always hydrate your soil before transplanting, rather than planting into dry soil then drenching. Transplanting into dry soil dramatically increases your risk of transplant shock.
When growing with salt-based fertility models, it is recommended to see approximately 10-20% runoff (where 10-20% of the water you apply will run out of the bottom of the container) to flush the soil and prevent salt buildup. When growing with organic amendments, especially in a supersoil like IndiCanja®, excess runoff can leach nutrients out of the soil. Our grower team recommends 0-10% runoff to preserve soil fertility when using organic amendments.
When to Water Your Plants
Once you’ve determined generally how much water your cannabis needs, the next question is typically, “how often should I be watering them?”
The frequency of watering will depend on environmental conditions, though many growers will recommend a general watering recommendation of once every 3-4 days. In very humid environments you may be able to stretch this out a bit, but you should be mindful of overwatering if your soil is taking a long time to dry out. The same concept applies to environments where your soil is drying out too quickly. It may be necessary to lower light intensity, increase humidity, or decrease temperature, if you find yourself needing to water your plants every day. Though it is generally better for plants to be slightly underwatered rather than overwatered, plants should not be dehydrated.
Some growers have careful watering schedules that they build based off humidity, temperature, soil type, and depth of watering. Others will determine when their plants need water by checking plant response or soil hydration. When soil is metered, many growers recommend keeping your soil within the 30-60% saturation range.
Outside of using gizmos and gadgets, the easiest way to determine if your plant needs more water is to feel the soil for dryness! If you stick your finger in the soil, your plants will likely need more water when the top 5 centimeters of your soil is dry. Depending on your container size, some growers will pick up their pots and use that as a more reliable indicator of how much water is in the soil. This is more useful for deep-set containers, where the soil may dry out at the top, even if it is properly hydrated where the roots are situated.
Overwatering Worries
We’ve said it a few times at this point, but overwatering can be a silent killer for your cannabis. There are many issues that overwatering can cause for your plants. When soil is waterlogged, roots don’t have access to oxygen, which is necessary for nutrient absorption (nutrient deficiencies can pop up as a long-term side-effect of overwatering, though by the time you’ll start seeing deficiencies your plants will likely have other compounded issues). This oxygen starvation can quickly result in root rot, which may be difficult to remedy. Fungus gnats thrive in wet environments, making overwatered plants or flooded catch-trays the perfect home for them. With so many things going wrong in overwatering environments, it’s important to know the signs of overwatering, and when to correct them.
The first thing you will see when plants are experiencing stress from overwatering is a pronounced drooping of the leaves. Leaf drooping may be slightly misleading, as this is the first thing that most plants will do when they are starting to experience stress. In the case of nitrogen toxicity (too much nitrogen in the soil), cannabis will form what is referred to as ‘the claw’ where just the tips of the plant will droop downward. In overwatering, the whole leaf will droop downwards, giving the plant a waterlogged appearance. Leaves will also start to yellow and die off. If you see these signs and have watered somewhat frequently, have heavy cannabis containers, or if the soil is wet and/or waterlogged, your plants have likely been suffering from overwatering.
Thankfully, most cases of overwatering are easy to treat as long as you can identify the reason why there is so much water in your soil. Are you watering your cannabis too frequently, not allowing the water to drain out? Does your container have proper drainage holes? Is your soil light and fluffy, the proper texture for healthy cannabis development? Are you watering your soil evenly, allowing for proper hydration and drainage? Go through this checklist and determine what the source of the overwatering may be, then correct that issue. This may be as simple as stopping watering for a few days and lowering your grow tent humidity to allow the water to dry out of your soil. However, in extreme cases you may need to unpot your cannabis plant and check the roots individually for rot or other signs of stress.
Unpotting your cannabis may cause too much stress for some plants to recover, so only do this if your plants are not responding to other treatment, and if you suspect that root rot may be to blame. Depending on how serious the root rot is, you may be able to save your plants with minimal dramatics. There is no reversing root rot, so the only solution is to completely clean off your plant’s roots, snip off any areas that are brown and soft, spray the roots with isopropyl alcohol or another sterilizer solution of your choice to kill off any pathogens, and repot your plant in fresh media.
Growing in a high-quality living soil like Purple Cow IndiCanja® can support healthier plant development and promote proper water absorption and retention. Diverse microbes in the soil can support and regulate water absorption, while the light and fluffy soil texture supports drainage and prevents waterlogging.
Plant health is inextricably linked with the quality of water you use, and how you apply it. With water being one of the most important inputs your plants consume, many growers ruminate on how to optimize their plant watering schedule.
Still have questions on how to water your cannabis to grow better weed? Contact our experts!