About Weights and Yields
|Where's the real yield?
|The same harvest after being manicured and dried
by two different growers
|Grower A||Grower B|
|Reported Yield (Dry Grams)||86||259|
|Difference in reported dry weight||66% less than Grower B||300% more than Grower A|
Three things to understand about weights and yields
- How the manicuring process affects reported yields
- The impact water content (dryness) has on reported yield
- Using 25% of fresh weight is more accurate than reporting a yield's actual dry weight
In its own way, manicuring has some of the same pitfalls that water content presents to the drying process, but instead of deciding how much water should be removed during drying, a grower is deciding which plant parts should be removed during manicuring. Manicuring is a human decision making process, and a highly subjective one at that. It's not a cut and dry process, no pun intended.
Manicured cannabis is more potent than its unmanicured counterpart. To deliver the same quantity of THC from resins, an unmanicured joint would need to contain more cannabis to make up for the less resinous plant parts it contains. It's the same concept as watered-down whiskey, more volume is needed to produce the same effect.
The tradeoff for performing a high quality manicure is that there will be less finished product by the time the buds hit the scale. It's the age old tug of war between quality and quantity. Unfortunately, time and effort also factor in because the manicuring process can be quite tedious, and as with the drying process, two identical harvests manicured by two different growers will usually have different reported yields. If one grows for personal-use, and the other commercially, decisions about where the cola ends and the crap-ola begins can be further complicated by two opposing points of view. Personal preferences do make a difference in reported manicured weight.
So how can we tell what kind of manicure a yield receives?
One way is to compare the reported manicured weight to the gross weight so we can see how much harvested material ended up on the trimming room floor. That would give an indication to the value of a crop (or strain), how much of itself it gave up in usable harvest. Another way is to compare reported manicured weight to the weight of unmanicured (raw) colas to see how much trimming the colas received. This indicates the before and after weights of just colas, for those interested.
The YOR tracks four types of harvested weights, but that's not to say growers report all of them. Though it does take time, effort, and extra planning to separate harvested material into several weighing piles, there were 22 harvests reported by two growers who did so.
The data suggests, on average, that 60% of the gross yield gave itself up as manicured buds, with the other 40% being leaves and scrap. The data also suggests that unmanicured raw buds, on average, lose about 15-20% of their weight to the manicuring process.
|Percent of Gross Harvest for 22 Reported Yields
*Computed field. Scrap=Gross Harvest(ALL)-Manicured Buds(MAN)-Leaves (LEF)
**One grower routinely removes undesirable plant parts during flowering, leaving no scrap and only unmanicured buds for harvesting. He does not weigh those parts, thus the extreme 0% figure under Scrap and 100% figure under Unmanicured Buds.
The reported manicured yield could range anywhere between 45% and 81% of the gross yield. Though the numbers do have merit, one must remember this data is from just two growers harvesting just four strains, but it is quite revealing of how these growers have worked with these strains.
One of the objectives of the YOR was to capture enough data, from enough growers, and for enough strains to be able to draw reliable and confident conclusions about a strain's value. The obvious implication is that some varieties may be more or less productive than others, not only in the gross yield department but in the usable manicured growth they yield as well. Some varieties would undoubtedly be more efficient to grow. However, that objective proved too ambitious given the rate at which this optional data became available.
One of the first things a grower decides when he's ready to store his manicured harvest is how much water should be removed during the drying or curing process prior to weighing the dried yield. If stored too dry it will be brittle and crumble to shake when handled, if stored too wet it will develop mold. If stored just right it will be moist enough to retain freshness but no so moist that it won't burn well, it won't become susceptible to mold, nor will it crumble when handled.
After some looking into, it was determined that 30% of the fresh harvested weight borders on being too moist (mold-threat), where 20% borders on being too dry (shake-threat). It was also determined that bone dry would be appx 15% of the fresh weight. Between 20% and 30% of the fresh harvested weight has been found to be an acceptable range to avoid both threats. This is how most growers dry their harvest, and more often than not they judge the degree of dryness using personal preference and experience rather than using a weighing scale. Nevertheless, it's in this range where the vast majority of growers weigh their dried yield.
Knowing that growers will report yields anywhere within that range posed an interesting challenge. The weight of water has an extremely strong influence on reported yields, two identical harvests dried by two different growers could have drastically different reported yields. If Grower A dried to 20% of the fresh weight, and Grower B to 30%, would the 10% difference really matter that much?
| How a 10% difference in dryness
can affect reported dry weight
|Grower A||Grower B|
|Harvested Fresh Weight||1000 grams||1000 grams|
|Weight Remaining After Drying||20%||30%|
|Reported Dry Yield||200 grams||300 grams|
|Difference in reported dry yields
from the same harvest
|33% Less than
|50% More than
When viewed with the focus on reported yields, a seemingly small 10% difference in dryness often explodes into something three to five times its magnitude by the time it's compared to another grower's reported yield. The impact dryness (water content) has on reported yield is indeed something to be reckoned with. In the long run, however, with enough growers and enough reports these variations average out. But for small comparisons as in the 1-on-1 example above, using fresh weight is essential if the proverbial thumb on the scale influence of water is to be avoided.
There's no question that when the subject of cannabis weights are brought up, the product is discussed in terms of its dry weight. This is something every cannabis user learns early on when he acquires his first ounce in the cannabis marketplace. Because fresh weight is a more accurate way of reporting yields, but dry weight had established itself as the default nomenclature when discussing cannabis weight, the YOR needed to find a way to avoid listing both types of weights so that users of the database wouldn't have to make mental adjustments for each yield report.
The answer was to allow actual dry weights to be listed when the fresh weight wasn't known, but when fresh weight was known to display its value in the database as if were a dry weight. That way the reader knows the yields he's viewing are only for dry weights, he doesn't have to mentally shift gears between fresh and dry with each new report, and at the same time the database can capture the more accurate measure of fresh weight when it's available.
To do this, the YOR uses a 25% conversion value to calculate dry weight from fresh weight. This value was chosen because published cannabis figures1 supported it, because preliminary tests by growers have shown it to be accurate, and because it's the average most likely to be encountered over the long term when working within the 20% shake-threat and 30% mold-threat threshold range. 1 Marijuana Botany 1981, RC Clarke, p153: Marijuana Grower's Guide - Deluxe Edition revised 1990, Mel Frank & Ed Rosenthal, p303
YOR records from growers who weighed their yields before and after drying were reviewed to check the efficacy of using this conversion value, and to check the low-high end points used for the threshold range. The review showed the 25% conversion value to be accurate, but that the low-high end points widened to 13% from the 10% originally estimated. The Average Conversion Value in the table below reflects a corrected conversion value based on the averages of real fresh weights and real dry weights. It's what the conversion% should have been, on average, to match the reported actual dried weights in the database.
|Results of the Review
|Average Conversion Value||25%|
The Perfect Storm
All the influences of manicuring and drying manifest themselves in the final dried yield figure. If you've seen the motion picture "The Perfect Storm", you understand how three storms can combine to produce an extreme-storm. Using that example, consider how the manicuring and drying processes can join forces to produce extreme yield reports such as those shown in the shell game at the top of this page. It's just a matter of the lows from each process combining in one report, and the highs combining in another, to produce a perfect set of extreme influences. Extreme cases were used here to make a point, and though they are rare they do happen. However, yield reports don't need to be this extreme to make a difference, there's plenty enough room between the two extremes to warrant serious concern. Unfortunately, with only dry weights to work with, there's no way to address that concern.
Not surprisingly, the answer to the shell game question is somewhere in the middle! Below is a table illustrating how those figures were computed, and what went on behind the scenes for them to turn out so different. Added to this table is a third grower who uses less extreme methods. Which dry yield do you think is the more realistic of the three?
|The same harvest after being manicured then dried
by three different growers
|Gross Fresh Weight (grams)||1000||1000||1000|
|Fresh Weight After Manicuring||450
low 45% manicure
high 81% manicure
avg 60% manicure
|Manicured Weight After Drying
(reported dry weight)
low 19% dryness
high 32% dryness
avg 25% dryness
|Difference in reported dry weight||66% less
than Grower B
than Grower A
1-The same fresh harvest was used by each grower for processing, gross fresh weight is the same.