There is a consensus among marijuana plant growers that hydroponically grown cannabis plants grow at a much faster rate than soil, if all other conditions are the same within the environment. This is presumably due to the controlled nutrient solution feeding the plant is given and increased oxygen available to the plants. There are even reports out there stating that cannabis plants that were started in prepared soil were ready for harvest later than their hydroponic counterparts that were started a full two weeks after the soil plants. This quick growth method gives more harvests because each crop needs less time to mature.
Soil-grown marijuana plants also typically end up slowing down once their roots become bound. Using hydroponics will give the grower even and quick growth without the hassles that come with soil growing. If you grow with rockwool, your plants will not end up experiencing shock from transplants either. The simplest system to use when working with hydroponics is the system that uses wicks from reservoirs. This is considered a passive method of hydroponics because it has no active water distribution requirements. This means you do not need to concoct a system of pumps, drains, meters for flow and a path for it all to take. This just means your marijuana plants will "wick" up the water they require from the "reservoir".
The wick portion of the system is a bit more complicated than the reservoir portion of the system because you need to cut and place wicks within each pot. This means you need to cut a hole in each and every pot that will hold your marijuana plant, and you need to figure out a way to keep the bottom of your marijuana plants above the liquid that will come into the base of the pot. You can do something as simple as put bricks into the bottom of a kiddie pool for your pots to sit on, or you can use nested buckets in the same way. We recommend the ease of the reservoir system over the wicking system.
The setup when starting a wick system is a pain, plus your marijuana plants sit up higher in your growing room. This means that you have less vertical space that you can use. You have to take special care when trying to stabilize the bases of your marijuana plants because if one happens to get knocked over, it will never grow the same because of shock and stress needed to help the plant recover. We recommend using rockwool slabs because a half slab fits perfectly within a litter pan for cats, leaving substantial room for root growth.
Growers will end up with very robust marijuana plants when this is their growing method because of how much oxygen the roots are able to get. If you use a reservoir you will end up with almost the exact same rate of growth as the wick method, but you will not have as much work to do. All you have to do to water and feed your marijuana plants is add some nutrient solution to your reservoir a few times a week. The kitty litter pans can be easily moved and do not take up precious vertical space. Traditionally, hydroponic marijuana pots are full of a lava and vermiculite mix in a ratio of 4:1. You will then add one tablespoon of Dolite Lime for each gallon (3.5 L) of growing medium that you use.
These mixtures will then soak up and retain a lot of water for your marijuana plants while still offering incredible drainage and oxygenation for the roots. The only downside is this mixture cannot really be reused because there is no real way to sterilize the mixture. We recommend small pieces of lava, between 3 and 8 inches (7.5 and 20 cm), that have been thoroughly rinsed until the dust is gone. You will need to moisten the vermiculite as it is dangerous when it is dry (always have a mask on) and then mix this into your growing pots.
A square pot will hold more than a round pot will. You will notice the vermiculite settling down after continuous watering from above, so make sure this only happens occasionally. Add extra holes into the bottom of each pot so the roots can wick up what they need as they need it. You will want 1.5-3 inches (4-7.5 cm) of water within your reservoir to start, allowing the liquid to evaporate some between each watering. You will have more success using less water and just watering your plants more often because this gives the roots additional water. If you need to go anywhere, you can fill your reservoir completely, allowing your plants to be self-sustaining for 2+ weeks.
The floral foam made by Oasis is an exceptional medium for hydroponics. Aerating it with holes will make it perfect for germinating new plants or clones. This will let growers use Rockwool once roots are established. Floral foam will not change your pH, making it ideal to many growers. The expense of floral foam is the only real drawback for most growers. It is not easily reused, but it is definitely quite popular. Rockwool is now beginning to take over in popularity for having many of the same benefits but also being reusable. You cannot overwater Rockwool and you do not need to transplant when you are using this medium. All growers need to do is put the starter cube on top of a bigger growing cube and that's it! Some prefer saving money and using soil, so if you're going that route, we recommend using Perlite.
You can use Perlite with lava or instead of it to avoid the dust rinses that come with lava. Even though Rockwool is a little more expensive, it often takes a grower wasting days transplanting for them to fully appreciate the usefulness of Rockwool. The expense also decreases when you calculate in the savings of having a reusable medium and decreased time from no more transplanting. Rockwool easily holds 10 times the water as soil can, but you never have to worry about overwatering your plants. It is as simple as starting off with a Rockwool cube and then moving that cube to a slab when the plant is too big for the cube. When you break down the cost over 3-5 crops, Rockwool costs the same or less than lava and vermiculite. Vermiculite also brings the danger of using it while dry (or the dust drying on your skin when it is used wet) so Rockwool is our medium of choice for hydroponic growth.
The only real downside to using Rockwool is the pH. It is alkaline, so growers must use an acid within the nutrient solution to bring the pH from about 7.7 to about 6.5 for marijuana plant growth. We recommend using vinegar. Rockwool can also slightly irritate skin when it is dry, but this is not a problem when it is moist. If you are going to use Rockwool, you will need to pretreat it by soaking it within fish emulsion combined with a solution of trace minerals and phosphoric acid (to lower pH) for approximately 24 hours, and then rinse the slab off. This will create neutrality within the Rockwool. You should use hydroponics for either greenhouse or indoor growing to help you achieve harvest sooner than other methods. Daily watering while using hydroponics will also help you have increased growth. The primary difference between soil and hydroponics is the medium's ability to hold water yet oxygenate the roots of your marijuana plants and pull only the necessary nutrients from the nutrient solution into the plant, increasing the health of your plants.
Using hydroponics will make it to where you have many less worries about your marijuana plants, such as oxygen problems or mineral buildup over time. You can use smaller growing containers with hydroponics than you can with soil for equally sized plants. One example is how well a 0.75 gallon (3L) container can be used until harvest for hydroponically grown plants but not with a soil-grown plant. It would cut off the plant's ability to eat and breathe properly, causing root binding. The nutrient solution gives hydroponically grown plants the necessary oxygen even if the plant does become root bound in a smaller container, allowing the plant to grow strong.
Each marijuana plant gets its food from the watering of the nutrient solution, giving the grower the ability to give their plants only the nutrients the grower wants to or the plant needs, helping boost each phase of growth from the increase in elements. You can add in a bit of automation for this type of growth as well if you start a drip system. You will end up with faster growing cannabis plants when using hydroponics, giving you an earlier harvest. It does make a lot of sense to use a hydroponic system when you can so that you end up with the most desirable end result possible from your marijuana plants.
Do not ever let your plants dry out completely with a hydroponic system because this will instantly cause root damage. If you have to be gone for a day (or longer) make sure the reservoirs are filled before you leave. The active methods of hydroponic growth are not mentioned here because we are trying to stick with the simplest methods of growing marijuana plants. If you end up using a pump, make sure to change your nutrient solution monthly, but reservoir systems get to avoid this step. You only have to rinse off your medium monthly to keep salt build up at a minimum. Pure water poured over your plants works perfectly.
Changeup which plant foods you use regularly so that your marijuana plants can pull in different nutrients as they need them. Each phase of growth should have at least two types of plant food so you can avoid deficiencies. If your pH is going down too quickly, you will need to change your nutrient solution more often than monthly.
Cationic exchanges between the solution and the marijuana plants usually create an acidic ph within your nutrient solution, starving your plants for nutrients. This is why you must regularly check your pH levels-preferably with every watering. If you notice algae growing over your medium, do not worry. It is quite unsightly but not harmful. If you want to avoid having a green Rockwool slab, you can cover the slab with plastic and just cut out the necessary portions for exposure to grow your marijuana plants. It is a simple process to cut a slab into two halves and then it already has plastic on it to help you out.
You can then cut out 2-4 inch (5-10 cm) holes in the plastic on top for your starter cubes and then put the whole ensemble into the litter box, creating an environment perfect for pre-treatment (described above) and then growth! Rocks on the top of growing medium can help you avoid algae if you are not choosing to use Rockwool.
Want to read more about marijuana? Go to our marijuana grow guide.