Growing Medical Marijuana

WA Department of Health Rules define the 60 Day Supply limit as up to 15 plants and 24 ounces of dried medicine.  Here, we provide some ideas on how to grow medical cannabis legally, without the risk of arrest.


Cannabis is a hardy weed that grows vigorously.  If you throw a few seeds on the ground in June, and pray for rain, you might just find a huge bush of pot flowers in the fall.  But that wild mess of green vegetable matter will definitely not be suitable for medical use by terminally ill patients.  The orderly production of fruiting plants is much easier to plan than to execute, and cultivation of cannabis for medical use is a fine art that requires years of experience to master.  The following profiles on potential yields presume the grower already has the prerequisite education and expertise in cannabis cultivation.  Novice cannabis growers will not be able to replicate these numbers in most cases.

The assortment of varieties of medical cannabis is another uncontrolled variable.  Some of the most potent marijuana strains are derived from crosses between the Indica and Sativa varieties, which tend to have greater stem length creating slightly less flower nodes, and therefore less finished medicine than the pure Indica varieties that are usually preferred for indoor production.  (Tall Sativa strains are more suitable for outdoor gardens, which are not specifically covered here.)  The yield estimates given may have significant variation depending on the varieties and methods employed.

Patient use

The issue of patient use is separate from but fundamental to a realistic understanding of these limits on cultivation.  In service with marijuana patients in and around Seattle, I have conducted a survey through patient self-reports in written correspondence incorporated into the medical records of more than one hundred Lifevine members in the Seattle area.  This patient population is comprised of approximately 50% HIV/AIDS patients with the remaining categories of Cancer, Crohn’s, epilepsy, Hepatitis C, Intractable pain, multiple sclerosis, and other illnesses accounting for the other half, Hepatitis C being the second most common ailment in this population.   From this and other studies I have conducted including years of interviews with legally qualified patients  in WA, OR, CA, and MT, I was able to determine and document the range of use of the overall population in a bell curve.

In most cases, marijuana patients use cannabis every day, though finances and availability may forestall their consumption.  A few patients may use as little as a gram or even a half of a gram per day.  That percentage is as rare as the most copious users who may use more than an ounce per week.  Though sources have claimed that some patients may use as much as one ounce or more per day, I find that theoretical notion unrealistic.  Two or at most three ounces per week are the highest amounts I have personally known in my decade of research on the subject.   On average, the middle-range of marijuana consumption by qualified patients is usually 14 to 28 grams per week of high-quality cannabis.   Again, some may need more due to potency issues as well as the tolerance factor that allows increased consumption with repeated exposure leading to diminished psychoactive effects.   For convenience, we shall presume the average patient, if given the availability, will consume up to one full ounce per week; hence, eight weeks' supply equals eight ounces of dried flowers.

Cultivation Profiles

Examples given here are general and do not account for the many pitfalls and hardships encountered by novice marijuana growers.  These estimations presume complete success in all stages and have no margin for error.  Without a doubt, maintaining a continuous supply for a typical cannabis patient with only 15 plants is a technical feat not to be accomplished without a huge investment of planning and effort. 

One must first obtain marijuana plants, which may itself be a somewhat daunting task.  If starting with seeds, they must be sprouted and grown to adult maturity to cull the males.  Medical cannabis is almost universally “sensimilla” (without seeds) because the potency of the cannabis is increased when female plants are not pollinated.   That “sexing” process can take two to three months.  During that period, a law-abiding grower would have to “sex” only 15 plants, and would be forced to destroy half – the average number of males.  (This is one area where a physician could not be called to testify on a botanical question, if the defendant needed to justify the possession of 30 plants that were intended to be culled long before a potential harvest.) 

Any sort of meaningful breeding program is unworkable with only 15 plants in the garden.  (Realistically, only collective gardens can undertake breeding programs under the new law.)    For simplicity of argument, we presume the patient may obtain one female plant through a seedling process or another source, and then must grow that single plant to generate progeny through cloning, the most common method of propagation.  

Profile 1:
One mother plant provides the source of 14 more.  The patient requires 8 ounces of marijuana in a 60 day period.   It will take 90 days to grow those 14 small plants large enough to yield slightly more than one half ounce of medicine each, totaling the required 8 ounces.  However, because it takes 90 days to grow a 60 day supply, using this method the patient fails to maintain a constant supply.

Profile 2:
One plant provides the source of 14 more, and again the patient requires 8 ounces per 60 days.  If the growing time is increased from 90 to 120 days, it is possible for the experienced grower to produce 16 ounces or more of finished medicine.  Thus, the patient is able to maintain a constant supply, except for the small matter of the next generation.  In order to insure the next cycle is on track, at least one plant must provide the next set of starts, and those must be cloned and rooted while the previous 14 are almost ready for harvest.  (This is another area where a testifying physician could not answer a botanical question, if a patient needed to justify the possession of 14 large plants and 14 small starts during the short period where rooting and the final weeks of flower development could overlap.)  

If the grower is a strong expert who has overcome the many pitfalls and difficulties associated with producing huge plants, it is possible to produce two or more ounces per plant in a 120 day period.  Because there is an additional allowance of 24 ounces of finished product, it is even possible for the expert grower with average needs to maintain a 60-day supply while possessing only 15 plants.  However, there is also the risk of exceeding the 24-ounce limit by producing 14 plants bearing two ounces each, totaling 28 ounces, or more.  This method presents a complication, when the patient requires more than one ounce per week.  In that case, the grower might not be able to maintain a constant supply without exceeding the limit.

Profile 3: 
One plant provides the source of 14 more, and again the patient requires 8 ounces per 60 days.  However, in this example, the patient does not want to wait 4 or 5 months for harvest. The grower propagates 7 starts at a time aiming for a two-legged cycle.  (This method requires at least two separate grow rooms to accommodate the two stages of development.)

7 plants grown under 1000-Watt lights, with proper pruning and staking, may produce the 1.15 ounces required to satisfy the 8-ounce requirement in a 100-day period of growth. The second 7 plants must then enter the cycle about 30 to 40 days after the first 7, to develop another 8 ounces for the following 60-day period, ad infinitum.  Because of the allowance of 24 ounces dried medicine to be possessed in conjunction with the live plants, it is possible to place the second set sooner than 30 days after the first set of 7, thereby increasing the second cycle’s yield at harvest, potentially leading to a surplus under optimum conditions.  he technique is not as complicated as it may seem, but insuring precise yield results can only be accomplished through experience.

The cycling of cannabis plants through three stages of development – small starts, mid-size vegetative plants, and larger flowering plants – is clearly the most rapid and most productive method.  However, the technique requires ample floor space, drainage, air filtration and venting, management of growing media, and of course, at least three high-voltage light systems.  Rent, electricity, hardware selection, installation and maintenance and time-consuming labor, all add up to a huge burden few severely ill individuals can bear.

Profile 4:
When a group of fup to ten patients pool their resources and cultivate cannabis together as one legal entity, the practical difficulties associated with plant limits described above are largely obviated.  Due to the cost and time commitment needed to produce the amounts of medicine listed above, many patients have joined collective cultivation groups.  In collective gardens, 15 plants per patient is quite sufficient; however, such patient groups must now maintain the new threshold of 45 plants per garden, in accordance with the 2011 amendment to WA state law RCW 69.51A, which assumes that not every collective member will require the maximum allowed number of plants.


To comply with legal requirements, cannabis cultivators must have strong knowledge of this little-known subject.  In virtually every example, first-time growers do not produce large amounts of high-quality medicine.  On the other hand, there are also a few cases, where a novice has inadvertently over-planted and produced far more than intended.  The new legal constraints are a challenge, but livable given adequate planning and effort to avoid the numerous difficulties and risks involved with growing medical cannabis. 

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