Making informed choices in grow mediums is a necessary step for any craft grower
In just about one month medical cannabis card holders will be legally permitted to grow up to 5 plants without persecution in Illinois. Patients are eager to grow craft cannabis at home, and while dispensaries are sure to have some great herb and concentrates to indulge in, most of us will be looking for the best way to save money, and have some fun along the way. In this post I will go over some of the most popular methods of growing cannabis hydroponically. Cannabis is heavily influenced by its inputs, and choosing a medium and nutrient program can have very different outcomes depending on which direction a craft/home grower takes.
Indoor hydroponics will be the most common way most patients will be seeking to grow their own. While hydroponics may sound like an activity for advanced horticulturalists to practice, in reality it is straightforward and practical when quality and yields are priority.
Hydroponic growing is feeding a nutritive solution to plant roots either suspended in solution or supported by inert medium. Within this broad practice there are number of things to consider, including the type of system, the medium in which to grow, and which nutrient program to feed your plants. While this doesn’t include every single method or medium to grow craft cannabis, it is sure to help the budding grower make an informed choice
Choosing A Growing Medium
When choosing a medium a number of things should be considered. How much can I or do I want to carry? How big do I want my plants to get? Will I be reusing my medium? Hand water or automated irrigation? Is discretion necessary? Do I have access to the nutrients most suitable for this medium?
I had the chance to visit my friends at Chicago Roots Hydroponics and Organics to check out their selection of growing mediums as well as ask a few questions. These guys are plant nerds to the max, and have just about any item a grower could need to grow just about any plant they want, from aloe to orchids.
Soil-Less mixes
By far the most commonly used growing mediums for home growers and many craft cannabis cultivators would be soil-less mixes. These are usually blends of sphagnum peat moss, perlite, coco, and a pH buffer like gypsum or dolomite lime. Many of these mixes also come fortified with a small amount of dry nutrition amendments to help get plants a healthy start. Soil-less mixes like Sunshine #4, Pro-mix are forgiving when it comes to over-watering as they often drain very well. This drainage helps to prevent roots from drowning and rotting. The gypsum or lime help to provide calcium and magnesium while also letting growers irrigate with water or nutrient solution without having to worry about adverse pH swings in the root-zone.
These soil-less mixes usually require cannabis plants be planted in at least 4-5 gallons for a decent sized plant that may reach 3-4 feet tall, although as the old saying goes, ‘more root, more fruit’. Planting in 7 gallon pots and getting 7 ounces of dried flower is not uncommon when done well. The extra benefit of planting in larger containers is less frequent irrigation. One should only need to water at most once daily if the proper size container is used. For best results using soil-less mixes most growers find irrigating, then letting the medium dry out a touch before watering again is the best way to use this medium.
The drawback to these soil-less mixes is the weight of multiple bags and the waste after harvest, especially for patients with less mobility. Many folks will either replant in the same container, utilizing a no-till grow setup (though this is for folks with deeper understanding of regenerative horticulture). Composting the spent root-ball in an outdoor garden or compost pile is also a very popular way to keep using expensive grow mediums after their first use.
Coco Coir
Coco coir is my favorite medium to use in hydroponics. It is a bit less forgiving, but for a craft grower with a few grows of soil-less mix under their belt it is a good place to move forward and really find some quality and yields. Growers can use a broad range of container sizes, often reducing the size needed to grow the same size plant in a larger container of soil-less mix such as Sunshine #4 or Fox Farm. This means that larger plants can be grown in smaller containers. Less medium, less money spent, less to carry!
Coco has a soft, cake like texture and holds onto water and nutrients exceptionally well, while also allowing for plenty of aeration. Because of this plants thrive in coco and are able to be kept on frequent fertigation schedules.
Coco comes in pre-wet bags or in dry, compressed blocks. These blocks can be very easy to transport, but do require growers to re-hydrate, and sometimes wash salt from the medium
A few things to keep in mind with using coco, as it does have a few particularities and nuances that require a slight learning curve…
- If your coco source is unsure or does not explicitly say it has been washed, be sure to wash off any sea salt that may have accumulated from where it is sourced with 1-2 gallons of water per gallon of medium after initially hydrated.
- When plants are transplanted into coco, be sure to water thoroughly and then let them dry out. Repeat this cycle 2-3 times to allow for roots to ‘search’ for more water.
- Be sure to supplement with extra calcium and magnesium as coco has the tendency to hang onto these minerals.
- Specialized Coco nutrient formulas are available to growers to help remove some guesswork.
- Be sure to pH all water and nutrient solution to 5.6-6.0 every time in order to provide consistency to your plant and ensure proper nutrient uptake.
Coco is also a great medium to begin utilizing active/automated irrigation systems. These can either be recirculating or drain-to-waste, though my favorite method is using drip emitters. By using coco and increasing frequency of watering growers can use lower volume of solution more often. This helps to provide consistent saturation and pH levels throughout the day, and throughout the plant’s life-cycle. This also helps reduce the dosage of nutrient solution, saving money on bottled nutrients.
Rockwool
Rockwool is an inert medium made of molten minerals and stone. It has the same properties as insulation, and is actually becoming a popular heavy duty, sound and fire resistant home insulation, and also popular grow room insulation in the form of Roxul.
For our purposes we explain its use as a growing medium. Rockwool is very lightweight and drains very well, while also being able to hold water well for 4-6 hours. Rockwool is most often used on flood tables in recirculating systems, where solution is pumped into the flood table and many plants are fed at the same time. This action also works to mix and aerate the solution.
Rockwool often requires the use of salt-based nutrients, with organic nutrients being few and far between in application with this medium.
Rockwool is very easy to use, is lightweight, and does not take up very much space. This is a great benefit when discretion is needed or transportation or mobility can be an issue. Just like in coco, larger plants can be grown in rockwool as along as fertigation is frequent.
There are a few companies that make a rockwool specific nutrient regimen, but typically using a standard two part system with a bloom additive is all that is necessary. Rockwool is definitely best suited for a flood and drain table growing system. When using rockwool, always be sure to check nutrient solution ppm through electrical conductivity (EC) tests at no higher than 1.8 EC, and pH between 5.5-6.0 with 5.6-5.8 pH being the sweet spot.
Along with growing established plants, small coco cubes can be used for propagation via seeds or clones.
Hydroton and Perlite
Hydroton or expanded clay aggregate is a super fast draining medium, often used to mix with heavier grow mediums in order to give the medium more drainage, or as a standalone that requires very frequent irrigation. it is made by heating small bits of clay in a kiln to temperatures above 1,200 degrees Fahrenheit.
Perlite is made of volcanic glass that is superheated. Perlite comes in many sizes while hydroton is often found in only one size. Perlite has a higher porosity, allowing for a little bit more forgiveness when it comes to frequency of waterings, while also maintaining high drainage. Perlite creates a lot of dust and is almost always used to add into peat moss to aid in drainage. When using perlite, always use a quality dust mask and safety glasses, due to the glass like structure of the airborn molecules.
Hydroton and perlite requires the same specific variables to be dialed in as other hydroponic mediums (nutrient ppm, pH, and temperature), except that it also requires nearly constant water flowing over it and the roots. Without this constant movement, the large clay and the roots it supports will dry out in as little as 30 minutes. Because of this, hydroton is almost always exclusively used in recirculating systems.
Hydroton and perlite can also be used as a support medium for net baskets to allow roots to hang into a larger container in deep water culture growing or aeroponic growing. Hydroton and Perlite are favored as standalones due to the ease of cleaning and reusing for future grows.
Deep Water Culture (DWC)
Deep water culture is a method of hydroponics where the only medium is water, and some sort of support for the plant parts that aren’t roots. This usually means hydrodon in a small net pot, settled into a container lid, over a larger container where the roots are immersed into an aerated liquid nutrient solution. These are a very easy DIY solution for anyone on a budget.
This method can grow MONSTER plants, often capable of growing 1 lb plants. The most simple way to construct a system like this would be to use a dark colored 5 gallon bucket and lid with a net pot inserted into a hole in the lid.
The key to this system working well is having adequate aeration of the solution in the bucket that the roots hang down into. Without this aeration roots will die and rot, and likely cause disease. For anyone looking to have the highest yields in a hydroponic system while staying compliant with a 5 plant limit, this is the way to go.
Another benefit of DWC is that no grow medium needs to be purchased, or thrown away. just fresh water/nutrients once a week.
Drain-to-Waste or Recirculating?
When it comes to hydroponics, one must choose between a system which is drain to waste or recirculating. Drain to waste being the easiest, while recirculating may require more of a learning curve.
Drain to waste means that a grower is either hand watering or using a drip system to irrigate. Plants sit in either a drain table or into drainage dishes. Ideally not much drainage occurs during watering, but when it does, drainage dishes are either poured out into the sink, or the table drains into a sink or sump pump basin. These drainage dishes can also be filled with hydroton or perlite in order to catch any runoff from watering, while the pots sit on top of the hydroton or perlite. This way they don’t sit in solution and cause root damage.
Recirculating systems require a reservoir and a pump that frequently waters and then drains back into the reservoir. Weekly reservoir maintenance is recommended, with old solution replaced by new solution. Many growers incorporate a float valve that tops off water in the reservoir as it evaporates or is taken up by the plants during waterings.
One of the coolest parts of a recirculating system is the ability of a keen grower to check fluctuations in water and nutrient levels throughout the week and even throughout the day. As plants are watered, and solution drains back into the reservoir, an attentive grower can monitor how quickly nutrients are being depleted, and thus add more accordingly, and adjust mixing amounts from grow to grow. This is where things get extra ‘sciency’ and craft really becomes part of the practice.
Be sure your setup fits your lifestyle
While all of this requires some consideration, they must all fit into your schedule and how much you want to work. Consider how much automation you want to incorporate into your system, how much time every day you want to spend with their plants. If you can spend 30 minutes a day with your garden, consider hand watering, as your plants will get lots of attention and will love you for it. If you need to be out of the door quickly every morning and can only devote a couple hours a week at most to your garden, explore options in automated drip or flood/drain systems.
With all these considerations though, it is imperative that a good grower also has a dialed in environment, as a combination of consistent factors+quality genetics is the number one way to guarantee an outstanding harvest. We will touch on environmental requirements in an upcoming article.
Peace, and good greens!
