Lab Notes #2. Last time we found that caryophyllene, a heavier terpene, leads more strain profiles than myrcene, a lighter one, and we asked whether time on a shelf could tilt that balance. This week: two lab studies that timed how fast the smell fades.
October 2026. Sources: Ross and ElSohly (1996), Milay et al. (2020), and our first 12 US lab report explainers.
1. A third of the oil is gone in the first week
In 1996, two researchers measured the volatile oil, the aromatic fraction that carries terpenes, in indoor-grown cannabis buds. Fresh buds held 0.29% oil by weight. After a week air-dried at room temperature: 0.20%. After a further month in a brown paper bag at room temperature: 0.16%. After 3 months in the bag: 0.13%.
That is 31% less oil after the first week, and 55% less than fresh once the 3 months in the bag were up. Measured from the end of that first week, those 3 months took another 35%.
2. The lighter molecules go first
The mix changed too. Monoterpenes, the smaller and more volatile molecules (myrcene, limonene, pinene and terpinolene are all monoterpenes), made up 92.5% of the fresh oil. After a week they were 85.5%, after a month 67.6% and after 3 months 62.0%. Sesquiterpenes, the heavier group that includes caryophyllene and humulene, rose from 6.8% of the oil to 35.6%.
The authors report a significantly greater loss of monoterpenes than of sesquiterpenes. Two reassuring details: none of the major components disappeared completely, and people familiar with the smell could still recognize it.
This does not prove that storage explains our Lab Notes #1 result. It does show the direction is plausible: time tilts the oil toward the heavier terpenes.
3. A newer study: half in 4 months, cold or not
In 2020, a research team stored two cannabis varieties in the dark for a year, at four temperatures: room temperature (25 °C), 4 °C, minus 30 °C and minus 80 °C, each in triplicate. They measured 93 terpenoids, 37 of them in detail.
The average terpenoid level fell by more than 50% by month 4, and it was considerably lower at every temperature they tested. Colder was not automatically better: in the variety they charted at month 4, minus 80 °C generally caused the steepest decline. Ground samples came out lower than whole ones.
One difference from 1996: here the lighter and heavier terpenes followed similar trends. Two studies, two answers on which goes first. Both agree the smell fades within months.
4. What the label says about age
We checked our first 12 US state explainers for dates printed on the package.
Harvest date: 4 of the 12 put it on the label: California, Michigan, New Jersey and Ohio.
Expiration: New Jersey caps it at 6 months unless there is stability data to support longer, and a retained sample of each batch is retested at 6 and 12 months. In Pennsylvania the grower sets the expiration date and must hold stability data to back it.
Two different dates: in California the farm adds the harvest date and the distributor adds a packaging date later. The packaging date tells you when it was sealed, not when it was grown.
What this means for your jar
Look for the harvest date when the label has one. Keep the flower whole, in an airtight glass jar, somewhere cool and dark. Then trust your nose: smell it when you open it, write down what you notice, and smell it again a month later. WeedCentral keeps that note with everything else you log, so you can compare.
How we did this
Sources.
Ross SA, ElSohly MA. The Volatile Oil Composition of Fresh and Air-Dried Buds of Cannabis sativa. Journal of Natural Products 1996;59(1):49-51. doi:10.1021/np960004a
Milay L, Berman P, Shapira A, Guberman O, Meiri D. Metabolic Profiling of Cannabis Secondary Metabolites for Evaluation of Optimal Postharvest Storage Conditions. Frontiers in Plant Science 2020;11:583605. doi:10.3389/fpls.2020.583605 (CC BY 4.0)
Our first 12 US state lab report explainers, published August and September 2026 at weed-central.com/learn/coa. They summarize each state's rules; they are not legal advice.
Our arithmetic. The 31%, 35% and 55% figures are ours, computed from the 1996 paper's oil yields (0.29%, 0.20%, 0.13%). Every other number is as published.
Limits.
The 1996 study measured total steam-distilled oil from one indoor grow, stored in a paper bag. Today's lab panels measure each terpene separately.
The 2020 study used two varieties in sealed bottles at fixed temperatures in the dark: lab conditions, not a kitchen shelf. Its authors judged whole flower at 4 °C their best overall condition, weighing other compounds as well as terpenes. Our storage guide still says to skip the household fridge, where opening and closing it brings moisture swings.
"Harvest date on the label" counts only what our explainers list as required. A producer may print more.
This is aroma chemistry. Nothing here is a claim about effects.
Lab Notes is for adults 21+ where cannabis is legal, and it is for education only. You get it because you subscribed to Lab Notes, and the unsubscribe link is at the bottom of every issue.