Almost all growers that have experimented with hydroponics have reported that their plants grew faster than when they used soil. This was with the same strains, genetics, and conditions. Hydroponic growing takes a lot of work, and you have to pay careful attention to the nutrient levels. With this style of growing, plants get more oxygen, allowing them to grow quicker. One specific report said that the hydroponics plants that were started 2 weeks after the soil plants actually matured first!
The faster growth of the plants makes the total growing time go down, which also lowers your electricity bill. With typical soil growing methods, plants are “shocked” several times. For instance, every time a plant is transplanted, it goes into shock for several days, and will not grow much during this time. All these interruptions are minor on their own, but when it’s all added together, it really starts to add a significant amount of time to the total growing time needed to mature. Growing hydroponically completely eliminates these interruptions, and keeps plants from getting root-bound.
There are several hydroponic growing methods to choose from. Some take a lot of time and effort, while others are relatively easy. A popular form is called the wick and reservoir system. This is also known as passive hydroponics, because it doesn’t require a water distribution system. The thinking behind this system is that water will wick to wherever it needs to go if the conditions and medium are correct, without a pump, timers, etc.
The wick system takes more setting up than the reservoirs. The wicks must be cut and placed in the correct locations (in the pots), and small holes have to be cut in all of the pots. Also, some sort of shelf or spacer system must be employed, to keep the plants elevated from the water reservoir below. Marijuana is not like rice – it doesn’t grow well directly in water. You don’t have to over think this. It can be as simple as placing 2 buckets, one inside the other, or by using a kiddie pool with bricks or blocks in it, which the plants can rest on top of.
The initial setup for the wick system is quite a pain, and requires more work than the reservoir system. Plus, the plants have to sit up higher in the room, which uses up essential vertical growing space. Also, since the plants are so high off the ground, their bases are often unstable, and if you knock one over (God forbid!) the plant will have a lot of stress, and it will never be the same.
For those reasons, I recommend the reservoir system over the wick system. The reservoir system is pretty easy to setup, and requires only a good medium, and a pan to put the pot in. If you’re using rockwool, a half slab of 12” rockwool will fit almost perfectly into a normal cat box. I always recommend cat boxes to people who ask, because they are cheap, inconspicuous, and allow for the plants to grow well because the roots can spread horizontally. When you grow plants in cat litter boxes, they will be very strong and robust, as the roots spread out and collect a lot of oxygen and other nutrients.
Reservoir hydroponic growing is by far the easiest method, and surprisingly enough, plants grown this way will grow just as fast as any other hydro method. With this method, you really only have to check your plants every few days, when you add nutrients to their water. Of course you should still keep an eye on them, but overall the reservoir system takes much less work than any other hydro growing method.
In most hydroponic growing operations, lava and vermiculite are usually mixed (usually a 4:1 ratio). Dolite Lime is also good to add, roughly one tablespoon per gallon of growing medium. A medium made of these materials will store water very well and will wick, and also has good air storage capacity, and good drainage. However, you cannot reuse a medium made of these materials, as it’s nearly impossible to re-sterilize it once it’s been used.
The best lava to use is small, about 3/8” pea size. Be sure to thoroughly rinse the dust off of it, rinsing it at least 3-5 times. Vermiculite is dangerous when it’s dry, so be sure to wet it thoroughly, and wear a mask when working with it. Next, mix it all into pots. I recommend square pots as opposed to round ones, as they hold more. When you water your plants, most of the vermiculate will sink to the bottom. To prevent this, water only occasionally, and put more vermiculate near the top of the pots than the bottom. Next, punch medium-sized holes in the bottoms of all the pots, and add a decent amount of water to the pans below. The water will be wicked up by the roots, and the plants will only take as much as they need, allowing for optimal growing conditions. This is the main advantage of hydroponic growing.
When filling your reservoir, you should keep it in the 1-3” range. Allow the water to recede quite a bit between refilling. If you can, water more often and keep nutrient levels low, so the roots can get more oxygen. If you are going away on vacation, fill the reservoirs to the top. This will allow for around 2 weeks of constant maintenance-free watering.
Oasis floral foam is a great medium for growing hydroponically. The best way to use this foam is to put many small holes in it, and put your starts in it. After the plants have grown and are getting bigger, transfer the Oasis foam into larger rockwool cubes. Oasis floral foam is a good medium, but many complain about the high cost of it, compared to rockwool and other options. It’s also hard to reuse, especially since it crumbles easily if handled roughly. It’s easy to find though, and seems to be pretty popular at gardening and home improvement stores.
Rockwool cubes are usually my #1 recommended product for hydroponic growing. There are several reasons for this, but mainly because it’s reusable, and requires minimal setup. Also with rockwool, the plants are usually kept in better conditions, because it is literally impossible to overwater. Plus, there’s no need to transplant when you use rockwool, and any experienced gardener will tell you that transplanting disrupts plants and weakens them. If the rockwool cube you’re using becomes too small for a growing plant, all you have to do is get a larger cube and place it under the existing one. It’s as easy as that!
If you want to save money, or you just prefer to grow in soil, you have a few options. The best bet for hydroponic growing is probably Pearlite, mainly because it’s nice and light. You can use Pearlite in combination with lava, or by itself. Lava tends to be heavier, and requires more maintenance than plain Pearlite, or better yet, rockwool cubes.
However, like I said, I highly recommend rockwool. Besides the obvious benefits, rockwool is extremely stable, and rarely crumbles or breaks. It can also hold around 10x as much water as normal soil. This may seem like a bad thing, but it’s also impossible to overwater when using rockwool, as it allows for a lot of air to get to the plants – more so than normal soil or growing mediums. A lot of people complain about the cost of rockwool. Well, look at it this way: with normal soil, you have to buy new bags each crop. Rockwool can easily be reused 3-4 times, or more. So, you can basically divide the cost of rockwool by 3 or 4 times, and then compare it to the cost of soil. It will cost about the same, or even less than comparable mediums such as vermiculate. Vermiculate is, simply put, a pain in the rear. It’s nearly impossible to sterilize, and therefore hard to reuse. Plus, it’s dangerous when it’s dry. Even if you’re careful, it will be hard to keep vermiculate from getting on the floor or carpet. Since it’s so toxic, I don’t recommend using it indoors.
Rockwool is not a “wonder medium”, however. It does have a few drawbacks. For one, it is alkaline pH, meaning a nutrient solution will be required to make it acidic. I use vinegar, which seems to work well. Rockwool is also slightly irritating to the skin when it’s dry, but when it’s wet it can be handled without problems. It’s nothing like the toxicity of vermiculate.
If I’ve convinced you to use rockwool, as I hope I have, here’s how you should prepare it. First, presoak it in a solution of fish emulsion (which is smelly, so do this outside), trace mineral solution, and phosphoric acid (used to bring the pH down). Soak the rockwool in this solution for 24 hours, then rinse it clean. This process makes the rockwool fairly pH-neutral, which eliminates many headaches down the road.
The main difference between hydroponics and normal growing techniques is that hydroponic mediums are designed to hold water very well, but still allow for optimal drainage. The goal of hydroponic growing is to water constantly, allowing for less grow time, and more bud in less time overall. Plants grown hydroponically do not get nutrients from the soil, but instead, from the solution that you add to the water. This is why you must pay careful attention to the nutrients that go into your solution. Hydroponics allow for a lot of air to reach the plants roots, which is always good. It also eliminates worries concerning mineral buildup in soil. Growing hydroponically is difficult at first, but it’s worth it in the long run.
Plants grown hydroponically can use much smaller pots than traditionally grown ones. For instance, a ¾ gallon pot will be fine to grow a plant from seedling to maturity. With soil growing, this would not be possible, as the roots become root bound, and don’t receive enough oxygen if they don’t have sufficient room to grow. With hydroponics, lack of nutrients or oxygen is never a problem, as plants are fed and watered constantly, and enough oxygen is available for the roots at all times.
Another advantage of hydroponic growing is complete control over nutrient levels. Experienced growers know that at each stage of life, the marijuana plant craves different minerals. With hydroponic growing setups, you can supply the plant with exactly what nutrients it needs. Watering can also be made almost completely automated by using a cheap drip system. Growing hydroponically will also hasten the total grow time significantly, which means you can crop out more often. Hydroponics are usually meant for indoor grow ops, but it can be done outdoors if you have a greenhouse.
CAREFULL! When you grow hydroponically, you must monitor your plants carefully. If they are ever allowed to dry out too much, the roots will be very damaged, and your plants can die. If you cannot make time in your schedule to water daily, at least leave enough water in the pans to last until you can check on your plants next. The last thing you want to do is to lose a crop because you forgot to water!
The above explains passive hydroponic growing. There is a whole other set of techniques, known as active hydroponics. To be honest, I don’t see the point in going over them, when you could just make it easy and grow passively. If you’re circulating water with a pump, it’s necessary to change the solution monthly. But if you’re using the reservoir system, you don’t have to worry about any of that. All you really have to do is thoroughly rinse the medium once a month or so, to make sure the salt buildup doesn’t get too bad. You can do this by watering the top of the rockwool cubes with pure water, with no added nutrients. It’s also important to switch up your plant foods regularly, to prevent mineral and nutrient deficiencies in plants. It’s recommended that you change the plant food a total of 4 times, 2 for each growth stage.
You should be constantly monitoring pH when growing hydroponically. If you notice it’s going down too fast (meaning it’s too acidic), you should change the solution more often. Cationic changes cause almost all solutions to become too acidic over time, which weakens plants by not allowing for sufficient nutrients to be absorbed. Ideally you should check the pH level every time you water.
If the area you live in (or the room you grow in) is very humid, algae might grow on your rockwool, causing it to turn darkish green. To prevent algae from growing, cover the rockwool with plastic (the plastic wrapping it came in works perfectly). Obviously you’ll need to cut holes in the plastic so the plants can grow through it. If you’re growing in pots, you can use a thin layer of gravel on the top to prevent algae. Rocks will dry very quickly, so the algae won’t have a chance to grow. Contrary to what a lot of people will tell you, there are no serious negative effects from algae on marijuana plants. To me, it’s simply unsightly and an annoyance.