Hydroponic Growing with Different Mediums
In the wild, most plants, including marijuana plants, use soil as a grow medium. Indoor growers have another alternative, though. They can use hydroponic systems featuring various grow media to exert more control over nutrient distribution and maximize their yields. This option is a great asset to growers where the laws may still be unfavorable towards growing (like Kansas or Tennessee or in states where the weather simply demands indoor growing options, like Alaska or Wisconsin.
Weed plants grown in hydroponic setups have easy access to nutrients and carbon dioxide, which improves their efficiency and, in some ways, makes them easier to grow. Plus, today’s hydroponic growers have more options at their disposal than ever. Hydroponic systems require a substantial initial investment, though, so read on to find out about different grow media before investing in equipment to find the one that will be the best fit.
Rockwool
This light-weight, affordable mineral-based material is great at retaining water. It’s composed of basalt and silica compound and can be bought in different quantities depending on the scale of the hydroponic grow. Growers can purchase large, one square meter plaques of rock wool, small blocks of concentrated substrate, or bags of shredded material.
One of the best things about Rockwool is that it retains water well. That means growers don’t need to water their plants as often, which can cut back on both labor and costs. Just make sure to check the plants every day for signs of under-watering or over-watering.
In any hydroponic system, over-watering is actually just as dangerous to the plants’ health as under-watering because it deprives the roots of oxygen and places the plants at higher risk of being attacked by mold and other fungi. Keep an eye on the plants, hydrate them gradually, and avoid reusing water to help prevent fungal growth. Hydroponic systems that use Rockwool as a grow medium should never feature platters beneath the plants, as this encourages over-watering.
It’s equally important to purchase the right type of Rockwool. Never use the so-called “isolation” form of Rockwool, which contains chemicals that inhibit plant growth. Instead, purchase Rockwool specifically intended for hydroponic cultivation.
Pros of Rockwool
Rockwool is popular with commercial growers. It’s affordable, efficient, and great at retaining water, which makes it a good solution for grows of all sizes.
Cons of Rockwool
No substrate is perfect, and Rockwool is no exception. For one thing, it’s naturally alkaline, which means growers must neutralize it by applying an acidic solution of around pH 4 or 5 before using it for their plants, which takes a full day. Dry Rockwool is also a skin and lung irritant, so growers must wear protective gear like gloves, long sleeves, and breathing filters when working with the dry material. Once it’s been moistened, this isn’t as much of an issue.
Clay Pellets
Clay pellets are a great option for inexperienced growers. They’re easy to work with, don’t pose the same risks of over-watering as Rockwool does, and create channels for oxygen and nutrients to travel easily throughout the substrate, making it easier for the plants’ roots to find them. Plus, clay pellets can be sanitized and reused without risking damage to future plants, so they’re good for growers working on a budget.
Pros of Clay Pellets
Clay pellets have a high air holding capacity and create fewer blockages to impede nutrient uptake. They’re also easy to use, which is a huge plus for novice growers.
Cons of Clay Pellets
Clay pellets have a poor water holding capacity, meaning growers who opt for this medium need to stay on top of watering their plants. They’re also fairly expensive when compared to Rockwool.
Coconut Fiber
Growers looking for a natural hydroponic grow medium need look no further than coconut fiber, sometimes also referred to in the industry as coco coir. This material is created using the husks of coconuts. In nature, the husks would retain water and minerals for the coconut seeds to facilitate germination. Hydroponic growers can leverage this natural mechanism to grow pot plants, as well.
Coco coir is created by grinding up coconut husks into a soil-like texture. Properly ground coconut fibers look like peat moss, but they’re much more ecologically sustainable since they don’t require centuries to regrow.
Pros of Coconut Fiber
Coconut fiber has a water retention rate on-par with Rockwool, but unlike Rockwool, it can be reused. Plus, since it’s a natural material, it doesn’t pose the same risks to growers’ health when dry. Coco coir is also naturally resistant to bacteria and fungi, which means growers have less to worry about in terms of excess moisture. Like clay pellets, coconut fiber can be sanitized and reused in future grows. Just don’t reuse water and never use a platter beneath plants.
Cons of Coconut Fiber
Coco coir can be reused up to three times before it needs to be replaced. Growers will want to have plenty on hand in order to replace it in a timely manner.
Perlite
Perlite is an agricultural soil amendment made from igneous amorphic stone. In hydroponic grows, it can also be used as a stand-alone grow medium. It’s especially good for clones, seedlings, and vegetative plants in the early stages of growth.
Pros of Perlite
Perlite is a highly permeable substance, but it doesn’t retain excessive amounts of water. Instead, it allows easy nutrient and water circulation, which increases oxygen levels, enhances root development, and helps to prevent disease. Perlite is also remarkably light, which makes it easy to work with, and it can be mixed with other grow media to decrease compaction and improve circulation in hydroponic systems.
Cons of Perlite
The fact that Perlite doesn’t retain as much water as other grow media means the plants will need to be watered more frequently. Hydroponic systems that feature Perlite also require more frequent pH testing. Whether growers use Perlite as an additive or a grow medium in its own right, they need to wear masks when working with this material, as it produces tiny particles of dust that can cause lung damage if inhaled.
Vermiculite
Vermiculite is a hydroponic grow medium made from hydrated laminar minerals. It is sterile, non-toxic, and nearly pH-neutral. Some hydroponic growers think of it as a foil to Perlite, since it holds water extremely well but does not support healthy aeration and circulation. Most feminized seed growers mix vermiculite with other media, often including Perlite, to create a Goldilocks situation for water retention.
Pros of Vermiculite
Vermiculite doesn’t just hold water well. It also retains nutrients well thanks to its excellent cation-exchange capacity. It can also wick both water and nutrients upward to increase availability to plant roots.
Cons of Vermiculite
Vermiculite isn’t ideal as a stand-alone grow medium due to its poor drainage capacity. It can also disintegrate after long periods of use, which means it can’t be reused. Mixing vermiculite with a combination of Perlite and coco coir provides the best of all worlds for hydroponic growers willing to invest in multiple grow media.
Sawdust and Wood Chips
Sawdust, wood chips, and wood fiber are all made from natural wood, which means they’re completely organic and sustainable. It’s important to source wood-based grow media from a sawmill that doesn’t process chemically treated wood and sterilize them before use. Most organic hydroponic growers prefer wood chips or fibers over sawdust, as sawdust tends to become waterlogged, which can cause problems with mold due to inefficient oxygen circulation.
Pros of Sawdust and Wood Chips
When sourced from the right sawmill, these materials are affordable, organic, and sustainable. They retain water well and can be sterilized to avoid contamination.
Cons of Sawdust and Wood Chips
These natural materials are only popular among the most eco-conscious of hydroponic growers. Some of the same qualities that make them more sustainable also make them less efficient for this use, as they must be replaced each season. It’s also harder to regulate pH when using wood-based grow media, and if improperly sterilized, these media can encourage fungal growth. Even after sterilization, they can still encourage pests.
Peat Moss
Peat moss offers fantastic nutrient and moisture retention. It can be used either alone or in conjunction with other grow media when growing chronic seeds. It can be sterilized and reused for several grow cycles, and unlike other organic grow media it does not contain unwanted microorganisms and seeds. However, there is a reason peat moss, once a commonly used garden soil amendment, is at the bottom of this list. It may be organic, but it certainly is not ecologically friendly.
Peat moss develops only in a very specialized type of ecosystem. It requires cold weather, substantial moisture, high acidity, and an almost complete lack of air only found in peat bogs. Even in the perfect environment, peat moss takes several thousand years to form, so while it is organic it should not be considered a renewable resource.
Pros of Peat Moss
The main advantages of this medium are that it is organic, does not compact, and is great at holding water and nutrients. It can also be mixed successfully with many other grow media to improve aeration and balance pH.
Cons of Peat Moss
Peat moss’s chief downside is that it is horrifically unsustainable. Hydroponic growers in Vermont or Arkansas who care about the environment at all should look for more eco-friendly alternatives, several of which have already been described above.
The Bottom Line
Choosing grow media can be a bit tricky, especially for organic hydroponic growers or those completely new to this kind of setup. Remember that many grow media can be mixed to address potential pitfalls like excessive water retention or issues with pH balance. Some materials cost more than others, but the least expensive options, such as Rockwool, must be replaced more frequently. After investing in high-quality American seeds, It is also worth investing in high-quality grow media that can be reused safely to avoid incurring additional seasonal costs.
