So first of all we need to understand why autoflowers need water? Well, basically water is the plants fluid of life and it takes up more than 80 % of the plants total weight. When you water the soil water dissolves nutrients and then that nutrient rich solution is absorbed by the roots and transferred upwards to the stem and eventually to those green leafs. This flow of water from the plants roots to leaves is called the transpiration stream because when the water gets to leafs more than 99 % of this water evaporates into the air. The remaining water is used by the plant in the photosynthesis process.
What water to use for autoflowers?
Before watering the plant we need to know what kind of water to use. in all honesty any tap water will do just fine and many growers all around the world use plain tap water and grow beautiful plants. One more solution is to use rainwater, because it is almost pure from salts and other chemicals and cannabis plant will love it. Before watering the plants with tap or any other water you should let it sit for couple of days in open top container. This process will allow the water temperature to reach the temperature of the surrounding air and the autoflower plants like to be watered with water that is not too cold or not too hot because cold water can shock the plants roots and stun the growth for a wile.
When the water sits in the open top container there is another process occuring and that is the dissipation of Chlorine which can harm your plants if it is found in high concentration in your water when you apply it to your plants. This chlorine dissipation happens by releasing bubbles so for the first day or two you will be able to see bubbles form on the container walls and when they are gone this water is ready for usage. After your water has sat for several days in that open top container and is ready to use you also need to check it’s PH level!
The PH of the water you give your autoflowers should be around 6.5 to 7.0 but a little variance to each side won’t damage them that much.
When to water ?
This probably is the most asked question by new growers but the truth is that there isn’t one schedule or one amount of water that will fit any cannabis grow operation. There are too many variables to the equation – some of them are: size of the pot, soil composition, air temperature, air humidity, air circulation, plant size, plants age and so on. After this long list you can see that there is just too many of these factors and you can’t introduce one formula for every grower but a general watering guide can be established!
Watering before germination
Before putting your precious autoflowering cannabis seeds in the growing medium you need to completely saturate the soil from top to bottom. What you need to do is pour two or three times the amount what the pot can hold and let it run off the bottom. This pre-planting flushing process is needed for the whole soil to get completely wet. If there are some dry soil pockets then your plants roots wont grow there and those dry spots can also be good places where high nutrient concentrations can appear when they eventually get wet! When all the excess amount of water is drained away you still need couple of hours to let the soil dry up a little. This drying process means that the time before you can put your seeds in the pot, after completely saturating the growing medium, is somewhere from 3 to 5 hours depending on the surrounding temperature and how fast the water drains and evaporates.
In the germination phase of the plants life you should be very careful with watering because that autoflower seedling is very fragile and it will easily bend if you water the soil surface too hard. When that little sprout is in this stage of growth it is better to keep the surface moist but not too wet and it is better to use a hand sprayer to moisture the growing medium. When you are watering this little herb don’t pour/spray water directly on the stem of the plant but around it because it can easily get a stem rot or fungus/mold. Basically, you need to keep the surface of the soil wet and that is it for this stage of growth.
Watering after germination
After the seedling has established itself and the first couple of true leaves have shown you need to let the surface of the soil dry up before the next watering. When you see that the surface of the soil (2 to 4 centimeters, 1 to 2 inches) deep is dry then you can water it again till a little runoff water starts showing at the bottom of the pot. You can also use soil humidity meters for a more accurate reading but it is not necessary for beginner growers.
Over-watering is almost impossible to do in just one watering, it occurs when you water your plant too often and don’t let the plant use all the water before watering again. It is better to let the plant experience a little dry period than over watering it. If you over-water your autoflower plant the roots will not be able to get any oxygen so the plant will suffer and will start turning yellow. Over watering the plant also introduces the risk of fungus and root rot and those are some serious issues better avoided by just not watering your plants that often.
Over watering can be fixed by just letting the plant soak up all the water for a couple of days and dont give it additional water till the growing medium is completely dry again.
Under-watering isn’t as big of an issue because the plant can survive long periods of drought and the soil is kept well irrigated and full with nutrients when you underwater rather than over-water.
When your plant doesn’t receive enough water it will start to wilt, because the plant cells that kept stems and leaves rigid by the water pressure in the cells won’t be able to get enough water and start shrinking and your autoflower plant will start to wilt.
This process can be reversed simply by getting water to your plant as soon as possible and in a couple of hours those leaves will be up and they will look as new.
Best Watering methods (watering guide):
1) Watering when the soil surface is dry by pouring water till there is a little runoff water at the bottom of the pot. This method needs you to touch the growing medium and can get a little messy so avoid this if you need to do anything else in your garden.
2) Watering by the weight of the pot. This method is one of the easiest and most commonly used methods. After watering the pot feels heavy, but when the plant has used all the moisture your pot becomes light and you can water it again. You just need to lift the autoflower plant up every day and judge the weight of the pot. At first, it will be a little hard to know when to water but practice makes perfect and soon you will be able to tell when your plant needs water just by tipping the pot sideways.
3) The third and the most controlled method is to get a soil moisture meter that shows exactly how moist the soil is and you know exactly when to water the plant!
There is also a method that you can water your plants by pouring water directly into the planter tray and letting the growing medium and roots collect the water by sucking it up from the tray. This method is great for tall pots as it makes your plant roots to strive for water and grow deeper so you can get a much better root mass.