By:   Taylor Keselica

Hydroponics is the process of growing plants in water without soil.  In the absence of traditional soil, a plant is placed in a growing medium, or nutrient-rich solution, and placed in a container allowing for water to circulate throughout the system to support plant growth.

Hydroponics is a preferred method of growing in the medical marijuana industry as opposed to using traditional soil for a variety of reasons.  Hydroponics is an indoor growing process, meaning that growth is not limited by climate or season.  Hydroponics reduces the water and nutrients needed compared to growing in soil.  This reduction in water and nutrient use allows for lower costs and higher efficiency.  The bottom line is that growing hydroponically is faster and creates higher yields, providing medical marijuana growing facilities the ability to more quickly bring larger quantities of medicine to market.

Though hydroponics can be accomplished in many ways, the most widely used hydroponic system in commercial medical marijuana growing is the Drip Irrigation System (“DIS”).  The DIS system operates by placing plants in a grow medium – typically peat, coir or rockwool – in pots, grow-slabs or grow bags while a timer activates a submerged pump, allowing nutrient-rich water to drip onto the base of each plant through a small drip line.  The benefits are: faster harvests of cannabis, cannabis plants are able to be swapped out quickly and easily, the water flow is customizable with more control over the plant watering schedule, water frequency can be changed more easily, and the amount of nutrient solution each plant receives can be controlled more easily.

With the growing legalization of medical marijuana, more states are accepting and reviewing greater numbers of cultivation applications.  Because of the increase in cultivation applications submitted, applicants are looking to differentiate themselves with agency reviewers by employing new and improved changes over traditional cultivation techniques.  These new changes make it important to consider impacts on state environmental and energy resources. Hydroponics offers numerous environmental benefits.  Approximately 50% less land is needed for commercial medical marijuana hydroponics because plants can be placed closer together without causing problems in growth rates.  This allows for more land for wildlife reserves and less of a need to demolish forests to create medical marijuana farms.  Similarly, less land erosion occurs with hydroponic growing since tilling of land is not necessary and no significant changes to land must be made to support growth.  Hydroponics for medical marijuana growth contributes to less stress on the increasingly strained water supply since the water is either recycled or fed directly to the plants and retained for days or weeks in a water bank.  This means that there is no need to continuously pump new water into the hydroponic system, allowing for water conservation.

Another environmental benefit of hydroponics is less fertilizer use.  Decreasing the use of fertilizers creates less toxic waste such as ammonia and fluoride.  The significantly less runoff produced by commercial hydroponic growing means less poison in groundwater such as rivers and streams.  A reduction in groundwater toxins decreases insect and small animal deaths due to pesticide and herbicide use.  Additionally, commercial hydroponics drastically reduces the amount of pesticides and herbicides needed in the first place which means less poison on the cannabis plants being grown, directly benefiting patients.  Finally, hydroponics has a direct benefit on the environment through the reduction of fossil fuel consumption.  Hydroponics allows for local medical marijuana growing which means decreased pollution rates associated with transportation of medical marijuana from a farm to a dispensary.

The Pennsylvania Department of Health regulates the medical marijuana industry under Title 28, Part IX of the Pennsylvania Code.  Hydroponic growing is referenced only minimally within Title 28.  Section 1141.21 of the Code defines hydroponic nutrient solution, spent hydroponic nutrient solution and medical marijuana waste (to include spent hydroponic nutrient solution).  Hydroponic nutrient solution is defined as “a mixture of water, minerals and essential nutrients without soil used to grow medical marijuana plants”; spent hydroponic nutrient solution is defined as a “hydroponic nutrient solution that has been used and can no longer serve the purpose for which it was produced”; and medical marijuana waste is defined as “solid, liquid, semi-solid or contained gaseous materials that are generated by a grower/processor or an approved laboratory” and includes spent hydroponic nutrient solution.

Title 28, Chapter 1151 regulates medical marijuana growing and processing requirements and disposal, with minimal references to hydroponic growing processes.  Section 1151.27 regulates requirements for growing and processing medical marijuana and permits a grower to use a hydroponic solution “of a type, formulation and at a rate to support healthy growth of plants.”  Section 1151.40 regulates the management and disposal of medical marijuana waste and states that a spent hydroponic nutrient solution “generated or produced from the growing, harvesting or processing of” medical marijuana plants is to be managed by either discharging the solution into a permitted sewage treatment system, treating and discharging the solution into Pennsylvania waters with a National Pollutant Discharge Elimination System permit or water quality management permit, or by disposing of the solution in a municipal waste landfill in a container smaller than 1 gallon in size.  Pennsylvania courts have yet to hear case law on the use of hydroponics for growing medical marijuana.

While hydroponics is only minimally regulated in Pennsylvania, growers are instructed in Section 17, Part C of the Pennsylvania Department of Health’s Grower/Processor Permit Application to “provide a detailed summary of the methods and procedures that will be used for the growing of medical marijuana,” including whether hydroponics will be used.  The light regulations mentioned above appear to show that the use of hydroponics for growing medical marijuana, in Pennsylvania and otherwise, is at the discretion and preference of the growing facility.

In sum, hydroponics is not heavily regulated in Pennsylvania beyond the disposal of hydroponic waste related to medical marijuana growing.  Additionally, growing medical marijuana hydroponically provides greater benefits to the individual cannabis plants, the growing facilities and consumers, as well as providing major environmental benefits, making hydroponics the most popular and preferred method of growing medical marijuana among commercial growers nationwide.


28 Pa. Code § 1141.21

28 Pa. Code § 1151.27(d)(2)

28 Pa. Code § 1151.40(e)(1)-(3)

Pennsylvania Department of Health Grower/Processor Permit Application