Passive vs. Active

To begin, we must first understand the differences between passive and active systems. As you might guess, a passive grow system is one that requires minimal maintenance. Passive systems have no moving parts such as pumps or spray emitters, since they rely solely on capillary action to move water from a reservoir to the medium. These setups are great for beginners because they use soil or, more typically, soilless mediums and require the grower to manually water and feed the plants, thereby keeping new growers in their gardens for longer periods of time — the very best way to learn about plants and horticulture.

Examples of passive grow systems include wick-system setups, standard window boxes or simple gardens using potted containers. These types of systems are recommended for first-time growers, even if you have grander designs later on. Plants can be finicky, and before you spend loads of money on expensive equipment, it’s best to learn on the cheap.

For the intermediate to advanced grower, active grow systems can be a lot of fun as well as extremely rewarding, both in terms of quality and yield. Active systems encompass almost all of the other grow systems available on the market. These deliver water and nutrient solution to the medium and root zone using moving parts and energy. Cannabis grows quickly, which makes it an ideal match for active hydroponic systems.

Hydro vs. Non-Hydro

To break it down even further, active grow systems can be divided into two categories: hydroponic and non-hydroponic systems.

Strictly speaking, hydroponics is the cultivation of plants without using soil. However, these days very few indoor growers actually use soil. Instead, they prefer a soilless mix that is most often composed of a peat or sphagnum moss base. These mixes have a look and feel very similar to regular topsoil, but they usually have a few other additives mixed in (more on this later).

New growers sometimes think that using soilless mixes means that the grow system cannot be hydroponic — but, technically speaking, as long as the system doesn’t utilize actual earth soil, the system is classified as hydroponic. The only true non-hydroponic systems in use these days are outdoor or greenhouse gardens, and even then many growers use a soilless mix, as these mediums are usually sterile and come pest- and disease-free. Some of these mixes even have mild organic nutrients added to the medium, giving them an edge over conventional soils.

Types of Hydroponic Systems

There are quite a few commercial hydroponic systems out there today, available in grow shops and online. Some of them come as turnkey solutions for indoor growrooms, while others are scalable and customizable depending on your needs. The turnkey models generally include flood-and-drain or deep-water culture (DWC) units.

The latter are used more by intermediate to advanced growers and usually include top-feed setups that allow for a range of mediums and plant sizes.

Let’s start by taking a look at some of the easier-to-use beginner systems and then work our way into the more customizable aspects of indoor grow systems.

Ebb-and-Flow

These systems are among the most popular with first-time hydro growers and use a simple formula for garnering larger yields and potent plants: lots of water and lots of oxygen to the root zone. Of course, this doesn’t happen simultaneously. In fact, these hydro systems keep the plants’ roots in the open air most of the time — but when the water comes, it comes heavy.

Also known as flood-and-drain, these setups use flood tables, reservoirs, and pumps to feed plants water and nutrient solution and require mediums that can retain moisture for long periods of time. Pumps on timers flood the tables for short cycles and then drain the solution back into the reservoir (although some growers choose to drain the solution to waste and do not recycle it). The most popular grow mediums used in ebb-and-flow systems are rockwool and HEC (hardened expanded clay). Each one has its pros and cons, but for beginners, the choice is most often rockwool because it’s easier to start seeds or clones in these plugs and then transplant them into larger cubes or slabs. The one big drawback here is that rock- wool offers little help to beginners in the way of buffering for young plant roots as they adjust to harsher nutrient programs.

Advanced Grow Tip: An easy workaround in this regard is to start seeds or clones in peat plugs and then transplant them into netted pots filled with HEC. However, HEC may not hold moisture long enough for new plants, and thus more frequent waterings are required, which in turn necessitates more attention from growers. Another option is to create an HEC/rockwool crouton mix in which to nestle the starter plugs.

Deep-Water Culture

Deep-water culture setups are great for beginners and more advanced growers as well. DWC — also known as “bucket systems” or “hydro pots” — utilizes large buckets or containers, with netted pots sitting in a hole in the top so that the roots hang down into the container. These buckets are linked to a single reservoir, with the size of the reservoir ultimately determining how many plant containers can be linked together.

The system works by pumping water or nutrient-rich solution from the reservoir through irrigation lines to the base of each plant site. The plant containers then fill with water from the bottom up, saturating the roots. After a few minutes, the containers drain and recycle the water or solution back to the reservoir, with short- cycle timers repeating the process several times a day. Other DWC systems allow the water to sit until it’s completely wicked up by the plants’ roots and then refill the buckets using float valves as the trigger.

Advanced Grow Tip: There are quite a few different DWC systems, and most can easily be modified by intermediate-level growers. These systems will produce large, bushy plants, but they require a lot of attention and plenty of lighting.

NFT and Aeroponics

NFT (nutrient-film technique) and aeroponic systems are similar in that they both require the plants’ root zones to be completely enclosed in order to achieve the best results. For beginning growers, this can be a problem, as access to the root zone is important in identifying early problems within a garden. Additionally, there are a lot of moving parts in both systems that require time and attention.

NFT systems generally utilize a conduit in which the plant containers sit with the roots hanging out. Netted pots or basket containers are often used here. The roots grow down into the conduit, usually large-diameter piping or a rectangular trough. A thin film of nutrient solution is then pumped in and passes along the bottom of the root zone as the dangling roots wick up water and minerals.

Aeroponic systems work in much the same way — however, instead of a thin nutrient film passing through a conduit, these systems utilize sprayer heads that periodically emit a fine mist to the root zone. This mist is caught by the fine hairs of the roots, and the nutrients get absorbed easily.

Both NFT and aeroponic systems can achieve large yields and high-quality flowers, but they can also be difficult to manage, as they offer little to no buffering for delicate root systems. Getting the NFT solution to the proper flow lev- els in the conduit, or ensuring that all spray emitters (and the spaghetti lines feeding them) have the proper pressure in aeroponic systems, can be challenging for first-time growers.

Soilless Grows

As discussed earlier, soilless grow systems are still technically considered hydroponic because they use non-soil substrates as the primary medium. However, these grow systems do not conform to the general notion of hydroponics these days, as many of the standard hydro systems available are not a good fit with soilless mixes. For example, a grower who attempts to use a peat-based soilless mix as the medium in an ebb-and-flow system will find that it creates quite a mess, with the loose medium dislodging from the root-ball and being carried out of the plant containers to block drains, dirty reservoirs, and clog pumps and feed lines. In this type of setup, a more stable medium is required.

This is where top-feed systems come into play. These are currently among the most popular methods of indoor cultivation, as there are a variety of models that can be deployed and a variety of medi- ums that can be used in these setups. Let’s take a closer look at how these grow systems function.

Top-Feed Drip

Of the three types of top-feed systems outlined here, the drip system generally provides the most constant flow of water and/or nutrient solution to the plants. In these systems, the plants are best placed in individual containers so as to ensure that each one gets enough water and nutrients. These systems often use flood trays to catch runoff, which can either drain to waste or circulate back to the main reservoir.

From the reservoir, water is pumped through main lines up to the tables, where smaller irrigation or spaghetti lines feed the individual plant sites. Stakes are used to hold lines near the base of plants, and drip emitters at the end of the lines slowly drip water into the medium. Some growers choose to have a constant drip going during the “daylight” portion of the photoperiod, while others use timers to trigger drip cycles.

Advanced Grow Tip: Using a solid medium such as soilless mixes or larger rockwool slabs aids in staking drip emitters to the plant sites.

Top-Feed Spray Emitter

Spray emitters are the most popular top- feed system out there today. Many growers prefer the specialized sprayer heads over a drip-emitter system because they provide a more even watering through- out the entire medium at each plant site. In all top-feed systems, growers generally use two to four emitters per plant site, but when four spray nozzles are staked around one plant base, very even saturation can be achieved.

The only pitfall with this system is that it’s not ideal for some nutrient programs, especially synthetic nutrients that are heavy in salts. This is simply because salts build up quickly in thin irrigation lines and often clog spray emitters, which rely on tiny holes in the nozzle heads to create pressure and an even distribution of nutrient solution.

Top-Feed Timed Flow

These systems are almost identical to drip-emitter systems but rely on a timer to deliver a periodic flow of water from the reservoir to the plant site. This option can be useful in large, commercial-format grow operations with hundreds of plants, or in setups where the grower prefers to have only one emitter at each plant site. In this system, a nozzle or emitter isn’t necessary, as open-ended irrigation lines can be simply staked into the medium ready to flow.

Depending on the medium, growers can choose various lengths for each watering period and use short- cycle timers to generate several feedings per day.

Advanced Grow Tip: Most advanced growers use top-feed systems with soil- less mixes as their medium. However, it is often recommended that you measure the saturation point of your medium and then set your short-cycle timers to match that duration and then shut off. Next, measure the amount of time it takes for the medium to dry out, then add 15 minutes and set that period as the interval between watering cycles. 

About Soilless Grow Mediums

When choosing a soilless medium, it’s important to read the ingredients label carefully and have a good idea about what you desire beforehand. Most soil- less grow mediums are mixtures of the following components:

Peat 

One of the most popular soilless- mix bases, peat is the partially decomposed remains of vegetation and flora that have been preserved underwater or in a semi-aquatic state. Its look, feel and texture are similar to fine earth soils, and it is heavily loaded with organic minerals. There are three types of peat: peat moss, peat humus and reed sedge, with the first two being the more popular commercial forms.

Sphagnum moss 

Sphagnum moss (or sphagnum peat, as it’s also called) is the dehydrated residue or living portions of bog plants; it falls in the plant classification system under the genus Sphagnum. It’s usually pathogen-free, always light in weight, and has an extremely high capacity for water retention. Sphagnum is more desirable as a grow substrate than standard peat; however, its high cost has limited its commercial use.

Coco coir

If peat is the most popular choice as a soilless-mix base, then

coco coir is a very close second. It’s an extremely adaptable substrate that can serve many functions. When ground to

a finer consistency, coco coir makes an excellent base for soilless mixes, and when shredded into fibers or chunked into small croutons, it can serve as a great additive to peat-based mixtures, as these forms help aerate the medium. In any form, coco coir — which is made from coconut husks — is highly absorbent and can retain moisture while holding its form for long periods of time.

Vermiculite

Vermiculite is an aluminum silicate mineral common in igneous and metamorphic rocks. Mined heavily in both the United States and Africa, vermiculite expands noticeably when heated, making it lightweight and insoluble in water. Mostly used as an additive for soilless mixes, vermiculite is neutral in reactions and offers excellent buffering to the root zone while also holding moisture and nutrients very well due to its high cation exchange capacity (CEC). This makes it one of the best soil- less additives available.

Advanced Grow Tip: The term “peat-lite” refers to peat-based mediums that contain perlite or vermiculite.

Types of Hydroponic Grow Mediums

Rockwool

Rockwool (or mineral wool) is produced from various mineral sources. Once superheated, it is spun into fibers and then pressed into cubes or slabs as it cools. Mineral wool is used both for rooting, such as in rockwool plugs or small cubes, and as a grow medium in the form of larger slabs or crouton beds. Rockwool is sterile and inert and can be used in all kinds of mixtures or as a stand-alone substrate. The primary benefit of rockwool is that it retains substantial amounts of H2O while also allowing ample air to penetrate the root zone. One major drawback is that rockwool is not a forgiving medium, offering the least amount of buffering for roots than almost any other option (the only exception being HEC). Growers using rockwool need to know their nutrient programs and strains very well.

HEC (hardened expanded clay)

When heated, HEC can produce a tough and stable substrate that is porous and capable of absorbing decent amounts of water. However, like rockwool, HEC offers no nutritional value. Both HEC and rockwool can be difficult to master because they require the grower to intimately understand nutrients and ppm levels within the solutions for feeding. That being said, HEC is a great medium for use in heavy-watering hydroponic systems. The clay substrate is weighty enough to keep peat or rockwool plugs with rooted seedlings or clones in place during heavy water flows, and it also allows for easy drainage and extra aeration. Remember, roots breathe in oxygen, so airflow in the root zone is integral to healthy plant development.

Perlite

Although perlite is mainly an additive, some advanced indoor growers will go with levels in excess of 50 percent when adding it to their peat- or coco-based mixes. Perlite is a gray-white volcanic medium, usually mined from hardened lava flows. The crude ore is crushed and screened, then heated in furnaces to over 1,400°F, which expands the particles to small, sponge-like kernels that are lightweight and highly moisture- absorbent — their key feature.

Advanced Grow Tip: Creating custom blends using 50 percent perlite added to peat or coco bases is an excellent way to dial in indoor grow operations and match your strain to your medium. Cover the entire surface of any peat- or coco-based medium with perlite to help lock moisture in.