I get a lot of questions about watering marijuana plants. There are a myriad things that can go wrong when growing marijuana but most of the ones that you control revolve around PH levels. Your eyes are the first line of defense as you’ll be able to see problems ranging from misshapen or damaged leaves to fungus, but there are things that you can’t see.
It is therefore a very good idea to get a PH tester that enables you to check both soil and water. Electronic ones with digital displays are of course easier to use, but also more expensive. At any good home improvement or gardening store you’ll also be able to find liquid PH testers, and these do a good job as well and are not as expensive but may be a bit more complicated to use. In a pinch, or if you are on a budget, PH strips will work, but they cannot be completely trusted. If you find your readings are not jibing with what the plant or soil looks like then the tester may be the problem.
Sometimes, however, the soil readings may consistently be in a good range (between 6.5 and 8.5), your soil composition may be sound (whether you are using an organic mix or chemical solution) but there are still problems with the marijuana plant. In these cases the problem is likely the water. Often it’s the PH of the water (ideally between 5.8 and 6.5), but other times it may be as simple as over- or under watering the marijuana plants.
Overwatering is a serious mistake that is very common among new marijuana growers because the assumption is that since water is needed, too much of a good thing can’t be bad. The problem is that too much water deprives the roots of oxygen and so they slowly die. A quick and easy sign of overwatering is that the marijuana plant will droop and seem as if it is changing colors, the green luster turning yellow. Leaves will fall off the plant and eventually even leaves that look healthy will die and fall. Another problem that comes from too much water is that it can leech vital nutrients from the soil before the plants have had a chance to absorb them.
The easiest way to prevent overpowering is to check the soil before you water. Insert a ruler a few inches into the soil and if it comes out dry and with no soil adhering, then it’s time to water. Unless you are growing marijuana in a very arid environment, your marijuana plants will only need a good water twice or so a week. The reason for this is that the topsoil is not indicative of the moistness of the rest of the soil. lf you are using an irrigation system, then you’ll have to adjust either the flow of the water, or the distance of the spouts from the plant. This problem is unlikely to occur if your plants are in the ground since excess water will be absorbed by the surrounding soil, but if your marijuana plants are in pots, this could be a serious issue because they could develop root rot.
Root rot is what happens to roots deprived of oxygen, and it could kill your marijuana plant. A slightly involved way to control water is to add a small amount (a few tablespoons) of hydrogen peroxide to your water. This works because the chemical compound is comprised of oxygen, but it also has an added benefit: it will kill any bacteria in your soil arising as a result of the rot.
But if this doesn’t works your alternatives (searching for the roots that are affected, killing them, then transplanting to a larger pot; or cutting the plant down) aren’t very good.
Under watering is another serious problem and its effects will look similar, with the exception that the leaves falling off will be shriveled and decimated. The plant is literally dying of thirst and, as it starts to wither, it is using all the available resources on subsistence and so will let the leaves, the extensions, go. This means that during this period of its vegetative state, the marijuana plant will stop producing new branches and leaves. Even though you can correct the problem quite simply (add water) the effects may continue to be felt at harvest when your plants may be smaller and their smoke may be more harsh than expected.
Typically, any other problems having to do with water will be related to pH The problem will go something like this: the soil has a nutrient deficiency, so you attempt to remedy the situation by doing something like adding Epsom salts or worm castings, or you mix in a balanced organic nutrient mix with your watering regimen. After about a week, the soil PH levels begin to rise (soil is less acidic) but the plant’s problem is still apparent. Concerned, you add more nutrients either directly to the soil, or in a tea and the problem only seems to get worse, (the PH drops).
In cases like this, it is probably the water that is the problem, and so, before you completely lose your mind, be sure to test the water. Most major municipalities chlorinate their water to kill bacteria harmful to humans. This water should never be used when you are germinating marijuana seeds or flowering your plants, and if you must use it when your marijuana plants are in the vegetative growth stages you should let it sit for at least twenty-four to forty-eight hours so that the chlorine can evaporate. Chlorine is very acidic and, once added, it can lower the PH levels in the soils preventing the absorption of whatever nutrient or supplement you are trying to add.