Did you know cannabis plants are 90 percent water? Weed plants rely on many resources to thrive, but out of all of them, they consume water in the highest quantity. This is because water plays a fundamental role in every part and biological process of the plant, from its roots to its canopy, all the way down to the cellular level.
They transport water through their circulatory system to turn sunlight (photosynthesis) and carbon dioxide (transpiration) into food. Water also helps transport nutrients to the plant and, providing the pH level is sufficient, will help those nutrients absorb into the root system. Needless to say, water is pretty important to a cannabis plant’s health.
Watering cannabis plants seems like the easiest thing to do, yet many growers, especially those new to cannabis cultivation, make mistakes with watering. Overwatering is one of the most common reasons for all sorts of growing troubles such as nutrient deficiencies and cannabis diseases, although giving your plants too little water can also negatively affect their growth.
Your source of water
The quality of the water you give your plants makes a difference. Ideally, you could use filtered, or reverse osmosis water, but you may have some trouble finding reverse osmosis systems in a lot of hydroponics and gardening supply shops, depending on where you live. Most growers simply use tap water.
Tap water is fine but it should be left out for at least 24 hours to settle pH levels. Also, room temperature water is less likely to shock your plant. Once settled, measure the pH level of your water using basic testing strips then adjust the pH level using pH down solution according to your specific needs.
Generally, soil requires a pH level between 6.0 and 6.8 whereas other grow mediums require pH levels between 5.5 and 6.0. Check with your garden supplier about your specific grow medium’s pH requirement.
After the pH has been adjusted, it is time to add nutrients (provided your plants are past the seedling phase). Because nutrients can cause shock to plants if introduced too quickly, we recommend starting with about half to three-quarters of the recommended “dose” of nutrients according to the product label then slowly adding more until the full “dose” is reached.
Do not exceed one full dose of nutrients because this could burn your precious plants. If nutrient burn does happen, do not worry. Just act fast to flush the nutrients out of the soil before dropping the dose down again.
How often do seedlings need water?
Infant cannabis plants typically spend 1-3 weeks in the seedling stage. At this early stage, cannabis plants require a high humidity environment. Keeping your seedlings at about 70 percent humidity is recommended. Water must be applied sparingly at this stage. Wet the rooting medium and wait 2-3 days for it to dry.
Typically, growers start seedlings in small rooting cubes or coco perlite so very little water volume is required to keep the medium moist. The objective is a moist medium conducive to rooting rather than a soaked medium that can cause the roots to rot. An effective wet-dry cycle is what we are shooting for.
Usually, pure water is fine as most rooting cubes have some minimal fertilizers made into them. However, hydro growers typically use a nutrient-free medium like rockwool. In this instance, very low doses of nutrients will be required from the beginning. The rule of thumb is to use 10-20 percent of a nutrient dose and work up.
A cheap spray bottle is a handy tool to mist cannabis seedlings. Read the signs the cannabis roots give you. As the rooting cube becomes prickly with white roots it is time for a transplant.
How often do vegetative plants need water?
As cannabis plants enter vegetative growth they demand more water. As the plant begins to grow vigorously and produce more leaves and branches it needs more water.
At this point, growers are becoming accustomed to the plant’s habits and beginning to dial in a perfect watering schedule. Now plants will either be in final containers or at least more substantial pots than rooting cubes. The grower can begin to gauge the watering interval by weight comparison of wet and dry soil. Hydro growers will be gradually increasing paying close attention to the plant’s response.
Soil growers will probably be watering 1-3 times per week depending on container size. Usually, a simple light feed-pure water schedule is fine as most high-quality soil has sufficient fertilizers for most of the vegetative phase.
Outdoor growers in this stage need to check the moisture level in the soil by sticking their finger right into the dirt. Usually, when the first inch of soil is dry, it is a good indication that watering is needed. Luckily, depending on where you live the rain may take proper care of your plant and keep it sufficiently watered.
How to water cannabis during flowering
Cannabis plants in the bloom phase are mature and either the grower has switched to 12 hours of light or autumn has arrived. Plants will be in final containers by this stage and bloom nutrients will need to be integrated into water. Watering may be required 3-4 times per week at this point.
Regardless of the strain, as some prefer high nutrient doses in bloom while others like light doses, watering will become more challenging for soil cultivators. If the grower has been using just pure water and perhaps some rooting stimulants until now bloom nutrients will need to be dialed in immediately.
Hydro growers have a slightly smoother transition in early flowering as they will switch to bloom fertilizers and can work up from a higher dose depending on the strain. Some strains may require daily watering during bloom in a hydro system.
In late bloom, most growers reserve the final 1-2 weeks for flushing with pure water. Typically the volume of water typically fed to plants is at least doubled to flush the plant. Although some prefer to gradually flush for two weeks with the usual water volume.
Flushing is an important final stage to remove nutrients built up over the bloom period that may spoil the taste of the bud. It can also be used to remedy over-fertilization at any stage. The key is to never leave plants sitting in puddles of water if you large volume flush, in particular, make sure to drain the runoff.
Common watering issues and symptoms
When watering is not done correctly, you will start to notice it in your plants. Symptoms of a watering problem can appear in the leaves, stems, or even the roots.
Even if your plants are grown hydroponically, you could notice watering-related issues develop in the root system. Many times, a root problem is the actual source of many other plant problems (such as wilting or drooping), and its primary issue is watering.
Cannabis leaf symptoms:
- Brown leaves
- Upper leaves and newer growth affected
- Lower leaves and older growth affected
- All leaves affected
- Leaf tips are burnt
- Spots appear
- Slowed growth
- Leaves curling under
Cannabis plant symptoms:
- Weakened stems
- Slowed growth
- Plant wilting
- Plant drooping
- Slowed growth
If your roots have been damaged, it can take the plant a long time to recover. Plus, a lot of other things could go wrong before that recovery occurs. Plants with damaged roots lose their vitality and become very vulnerable to pests and diseases. Therefore, if you damage your roots from overwatering, you could easily kill the plant.
The number one issue around hydrating plants is over-watering. Overwatering is a serious mistake that is very common among new cannabis growers because the assumption is that since water is needed, too much of a good thing cannot be bad.
Do not make this mistake. If you are overwatering your plants, their roots will start to drown causing the growth of your plant to slow down or even stop. This happens because of the anaerobic condition that develops from an overwatered plant.
Too much water can moisten the valuable air pockets where oxygen is stored, making less oxygen available for the roots to absorb. The roots will consequently function incorrectly, lose their strength and potentially fall victim to pathogens.
Overwatering is unlikely to occur if your plants are in the ground since excess water will be absorbed by the surrounding soil, but it can happen in areas with poor soil.
Clay-based soils or soil that experiences heavy rainfall will not drain well. On the other hand, sandy soils might have drainage rates that are too fast. Know your soil and adjust your watering routine accordingly. The most basic way of combating an overwatering problem is to add in time between each scheduled watering, then allowing your plant some extra time to absorb smaller amounts of water until it appears happy and healthy again.
If your cannabis plants are in pots, it is easy to overwater. Without proper drainage, water will accumulate and drown the roots. Even with proper drainage, the roots could still receive too much water if it is happening too often.
Because overwatering starts at the roots, you may not see any discoloration to indicate a problem, such as with issues from other environmental problems. You will notice that the leaves begin drooping and the overall look of your plant will be tired and unhealthy.
Sometimes chlorosis or yellowing of the leaves develops, but you should not think you are fine simply because the leaves are not yellow. You should also not confuse drooping with wilting as they are caused by different problems. Drooping leaves mean the entire leaf is curling under or hanging in a manner that looks sad, not just the tips of the leaves. You may also notice leaves beginning to fall off, even ones that look healthy. This is never a good sign.
Too much water is also problematic because it can prevent the plant from absorbing enough nutrients. The water is washing out the vital nutrients that a plant needs before it has a chance to absorb them. Plus, if your soil is always wet, there is also a considerable risk of fungal growth and mold.
Underwatering is not as dangerous as overwatering, but it is still a problem. Its effects will look similar, except you will notice leaves falling off and they will look shriveled and decimated.
When a plant has been underwatered, it can die of thirst. As it starts to wither, it is using all the available resources and will sacrifice the leaves first. This means that during this period of its vegetative state, a weed plant will stop producing new branches and leaves, limiting its potential.
Even though you can correct the problem quite simply by adding water, the effects may continue to be felt. Because the plant’s growth was stunted, your harvest may be smaller, and the way the lower smokes may be harsher than expected. If a plant does not get enough hydration, it will not develop properly.
A lack of water can lead to many problems. Since water is essential for photosynthesis, the lack thereof will reduce the photosynthesis in the plant. Furthermore, to carefully manage the available water, the plant will close the stomata on its leaves. As a result, less water evaporates, and therefore the plant also absorbs less water. Consequently, it also means that no CO2 can go through the plant.
The lack of water supply also causes stagnation of the nutrient supply from the ground. Not enough nutrients mean a shortage in protein production. The cannabis plant will show signs of nutritional deficiency in no time. Adding fertilizer is useless because the plant cannot absorb it anyway due to the lack of water.
Underwatering also causes a plant to breathe faster. This is because the plant must put in a lot more effort to loosen the remaining water in the ground. This takes a lot of energy from the plant that can no longer be diverted to growth and flowering.