All plants need a plentiful supply of good clean water to grow. Tap water works ok but can often be high in alkalinity; if you are going to use tap water without a filter system then it is recommended that you leave tap water to stand for a couple of days to allow it to dechlorinate. You should also test its PH and make changes as necessary. Some growers prefer to use rain water, however, rainwater contains many pollutants and can vary wildly in its PH values and is therefore not recommended. It is possible to use tap water by providing optional calcium and magnesium components to the feed program, just check what amounts you have so far.
Supplying water to your plants is at the heart of your grow room. There are a whole range of automated watering systems to choose from.
If you are growing in soil and watering by hand your plants will need good drainage to enable flushing and avoid a build up of salts from the nutrients, they should not be left in standing water.
The exact frequency for watering your plant will vary according to size, strain, growth rate, temperature, size of pot and other variables. You should avoid saturating the plants while at the same time preventing them drying out. Put your finger an inch or two (2.5cm – 5cm) into the top of the soil. If this is dry then the plants need to be watered. With young plants this will be every few days. As the plants get bigger you will need to water more often with larger amounts. A large plant may require daily watering.
Observe the plants. Plants requiring water will begin to wilt and the leaves will droop. If you water when this happens your plants will revive within the hour. With practice, once you become familiar with your plant, you can catch it before wilting happens. Give enough water, directly onto the soil, so that it just begins to come out of the drainage holes at the base of the pot.
Water is used most efficiently if you give it during the plant’s morning photo period (remember its cycle may be different than the actual daylight cycle). A spray of the leaves during its evening is also beneficial. Remember to use water at room temperature to avoid shocking the plant.
pH for Marijuana
pH is the measure of acidity of any given substance. A pH of 7.0 is totally neutral, 1.0 to 6.9 is acidic and 7.1 to 14.0 is alkaline. An increase in pH from 7 to 8 is actually a tenfold increase, so be aware! The average pH of American tap water is around 8.0 Marijuana responds best to a pH level of between 5.5 and 6.5 when it is grown hydroponically. There are products available known as pH Up and pH Down. These will help you to regulate the pH of water and nutrient solutions. If you are constrained by budget you can use baking powder to raise pH or vinegar to lower it but this is not advised. You need to note that it is natural for the pH level of a reservoir to climb over time as the plant takes up more water than nutrients. This will usually take between 5 and 10 days to move the pH up from 5.5 to 6.5.
Most growers use a continuous pH monitoring device, there are lots on the market but you should never totally rely on this one system. You should use a backup system to spot check and calibrate the original… if both are reading the same pH then all is good but if both are different you really need a third device to see which one is actually right!
These machines actually block molecule sized substances that can measure as low as 0.0005 microns. The systems have membranes with trillions of little holes and the water is pushed through them with two outputs, one of brine or waste water and the other of pure water. You want a nice even flow of water through the reverse osmosis machine at a rate of around 60 pounds per square inch; if you find the pressure in your flow gets too low then you need a back up pump to stabilize it. Reverse osmosis machines do waste a lot of water though at around 10 parts per 1 or 2 parts of pure water produced. These are complicated machines and we would advise that you look at systems that include both a booster and a permeate pump. We have a full run down on reverse osmosis machines read more.