Yield of dried flowers weight in cannabis cultivation is a primary focus for every gardener, regardless if they are growing boutique, small batch artisan cannabis, or industrial, large batch, low cost flowers. A crop’s output largely dictates what it cost to grow it, which is to say, that when you do the math, having a large yield typically trumps the other variables within a cost of goods analysis. One would utilize this data analysis process to determine, for example, if a particular costly supplement is worth it, or what the return on investment might be on a state of the art lighting technology, or whether a particular genotype (clone) might be suitable for increased production in the garden.
For years cannabis cultivators would speak of their yields in terms of have many pounds or kilos they produced of dried, processed flowers, per 1000 watt flowering light. A good crop might have led the happy gardener to say, “I got 2 pounds per light!” Although this method of measuring a batch’s (or crop’s) result does give some indication of what was achieved, it does not account for the wide window of different genetics flowering times. While the right cut of Sweet Tooth #3 might finish in 42 days of flowering, a Super Silver Haze example may take as long as 84 days, double the flowering time, thereby it would have to yield double dried grams per crop as the Sweet Tooth to yield the same when you account for the time that the space was used to grow the batch.
In order to account for both the flowering time and the weight yielded from a particular batch, I developed a simple system useful in data analysis of true yield results and trends. First, the number of 1000 watt lights (LED, ceramic, or any modern equivalent, any space greenhouse or otherwise covering approximately 20 sq. ft.) used in the batch is determined. Then the total grams of dried manicured flowers and the days of flowering time are assessed.
The equation is as follows: YIELD IN GRAMS divided by NUMBER of LIGHTS divided by DAYS IN FLOWER.
Here’s an example: 1000 grams yielded, divided by 1 light, divided by 70 days in flower.
1000 divided by 1 is 1000, divided by 70 is 14.29. So this single light’s crop had a Gram per Day (GPD) average of 14 and change. No matter how large or small a crop is, it can be measured as such, allowing an equal playing field of crop analysis irrespective of crop size or time it takes to flower particular genotypes.
Here’s another example from a larger batch: 58,453 grams yielded, divided by 75 lights, divided by 67 days in flower.
58,453 grams divided by 75 is 779.37, divided by 67 is 11.63 Grams per Day (GPD).
Upon examination, most batches yield between six and 16 grams per day. Anything below is essentially crop failure, anything above, is phenomenal. I consider any garden to be operating at 10 or above to be doing well, with 12 as a target, and the potential to do better through tweaking the environment, nutrient regiments, and genotype (strain or cutting) selection.
The GPD model can be used to assess anything from the yields of a specific time period from a specific section of the garden, to an individual gardener’s effectiveness, or to assess the profitability of different genotypes from a batch of seeds. It can be utilized to compare facilities, or to fine tune strain specific nutrient regiments or determine the ideal temperature/humidity for different genetics. As the long as the data gathered is accurate, it can be the best tool to maximize a garden’s performance, which is the engine of profitability.
Whether you have a single light in your closet, or are managing millions of watts, or even a greenhouse, the GPD yield analysis model is the most effective was to monitor yield trends in your garden, giving clarity to the nuances of the decisions on makes that impact the bottom line on a daily basis.
By Ben Burkhardt