Quick answer
Properly stored weed stays fresh for about 6 to 12 months. After that it does not usually “go bad” so much as get weaker and harsher, because THC slowly breaks down into CBN. The exception is mold: fuzzy, powdery or musty-smelling weed has spoiled and should be thrown away, not smoked.
Key takeaways
- Dried flower kept in an airtight jar, cool and dark, keeps most of its flavour and strength for roughly 6 to 12 months.
- Heat speeds up loss: in a 2-year trial at 25°C, total THC in stored cannabis fell 21% and CBN rose about 28-fold, while sealed storage at 5°C showed no significant change over 3 months.
- Old, dry weed is usually just weaker and harsher. Moldy weed is different: white or grey fuzz, powdery patches or a musty, damp smell mean it has spoiled.
- Moldy weed cannot be saved. Mold can be present beyond the patches you can see, so throw out the whole batch.
- Buy amounts you will finish within a few months: smaller sizes cost more per gram but stay fresher.
Last updated 16 October 2026 · By the Bud Cargo team
How long does weed last?
Well-cured weed lasts about 6 to 12 months at close to full quality when it is stored airtight, cool and dark. It stays usable well beyond that, but it gradually loses aroma first and then potency. Weed left in a warm room, in sunlight or in a plastic bag declines much faster.
There is no printed expiry date on most flower because nothing dramatic happens on a set day. Two slow processes are at work: terpenes (the compounds behind smell and taste) evaporate, and THC oxidises into CBN, a cannabinoid that is far less intoxicating. Light, heat and air drive both. Humidity matters for a different reason: too much invites mold, and too little makes buds brittle and harsh.
| Age (stored well) | What to expect | Still worth using? |
|---|---|---|
| 0–6 months | Full smell and flavour; buds slightly springy | Yes, peak quality |
| 6–12 months | Aroma fading, a little drier; most potency intact | Yes |
| 1–2 years | Muted smell, harsher smoke, noticeably weaker effect | Usually, if dry and mold-free |
| 2+ years | Little aroma, crumbles to dust, much weaker | Safe if mold-free, but disappointing |
| Any age with mold | Fuzz, powdery patches, musty or damp smell | No, throw it out |
These ranges are typical for flower stored in a sealed jar at room temperature or below. Storage conditions move them more than anything else.
Does weed go bad or just lose potency?
Mostly it just loses potency. Dry, old cannabis that has been kept clean does not turn toxic; it becomes weaker, harsher and less flavourful. It only truly “goes bad” when moisture lets mold grow.
The best measured example is a 24-month stability trial of ground cannabis flower published in the Journal of Cannabis Research. Stored at 25°C for two years, the samples lost 44% of their THCA and 21% of their total THC, while CBN rose from almost nothing to about 28 times its starting level. Storage at 30°C changed the cannabinoids faster still. By contrast, cannabis sealed in foil and kept at 5°C showed no significant change after three months (Aviram et al., 2022). That study used ground flower in sealed cartridges, so treat the exact figures as a guide rather than a promise for a jar of buds, but the direction is clear: warmth costs you THC over time.
How old can weed be before it goes bad?
There is no hard cut-off. Clean, dry weed can be years old and still be safe to use; it will just be weaker and less pleasant. The real limit is condition, not age. Check it for mold, smell it, and feel it. If it passes all three, age mainly affects quality.
As a rule of thumb, aim to use flower within a year for the best experience. Beyond two years, expect a clearly milder effect and a harsh, papery taste.
Is 6 month old weed still good?
Yes. Six-month-old weed that has been stored in an airtight container away from heat and light is still good, and most people would struggle to tell it from fresh. You may notice a slightly weaker smell. If it has been sitting in a sandwich bag on a sunny windowsill, expect more loss, and check it for mold if it ever got damp.
How can you tell if weed is moldy?
Look for white or grey fuzz, a powdery white dusting, or dark spots, and smell for anything musty, damp or like wet hay. Moldy buds may also feel spongy or damp in the centre rather than dry. Any one of these signs means the weed has spoiled.
Mold or trichomes?
Healthy buds are covered in trichomes, the tiny resin glands that make good flower look frosty. The difference is in the detail:
- Trichomes sparkle, look crystalline and sit evenly over the bud. Under a jeweller’s loupe or phone macro lens they look like tiny mushroom-shaped stalks.
- Mold looks dull and cottony or web-like, sits in patches, often grey or off-white, and does not glitter. Powdery mildew looks like a flat dusting of flour.
What does spoiled weed look like?
Spoiled weed shows visible fuzz, grey-white powder or black and brown spots, and usually smells musty or sour instead of like cannabis. Weed that is merely old looks different: it is dry, faded in colour and crumbly, but clean.
Not all contamination is visible. A 2023 review in Frontiers in Microbiology notes that fungi such as Penicillium and Aspergillus can live on and inside cannabis without obvious symptoms, and can survive at moisture levels that would stop most other molds (Gwinn et al., 2023). That is one more reason to keep weed dry and sealed from the start.
Is it bad to smoke slightly moldy weed?
Yes, avoid it. There is no safe “slightly” with moldy weed. Inhaling mold spores can irritate the lungs and trigger allergic reactions, and the Frontiers review reports that smoking was the route of exposure in 89% of documented fungal infection cases linked to cannabis. The risk is highest for people with weakened immune systems. If you are unsure whether you have been affected, speak to a health professional.
Lighting it does not fix the problem: the same review notes that the heat of smoking may not be enough to kill all spores.
Can moldy weed be saved?
No. Cutting off the visible patch does not work, because mold spreads through a bud and to the buds touching it before you can see it. Throw out the whole container and clean the jar with hot, soapy water before using it again.
Will smoking old weed make you sick?
Old weed that is dry and mold-free will not make you sick in the way spoiled food does. It is more likely to taste harsh, make you cough and feel weaker than you expect. If old weed was ever stored damp, check it carefully for mold first.
How do you keep weed fresh longer?
Keep it in an airtight glass jar, in a cool, dark cupboard, at a steady humidity of roughly 55% to 62%. Those four conditions slow both potency loss and mold. Do not keep it in the fridge door, on a windowsill or in a plastic bag.
- Air: use a jar sized to your stash so there is little empty air inside, and avoid opening it more than you need to.
- Light: amber or opaque containers, or a closed cupboard.
- Heat: cool room temperature is fine; avoid spots near ovens, heaters or sunny windows.
- Humidity: a two-way humidity pack keeps flower in the 55–62% range. Wetter than that invites mold; drier makes buds crumble.
Our two storage guides go deeper: how to store weed and keep cannabis fresh and how to store cannabis properly. If you want to keep a large amount for months, read whether you can freeze cannabis first, and if your buds have dried out, see how to rehydrate dry weed.
How much should you buy so it stays fresh?
Buy what you will finish within a few months. Larger amounts are much cheaper per gram, so the trade-off is real: an ounce is the best value if you will get through it, but a smaller size is better than an ounce that sits in a drawer for a year.
On Bud Cargo’s live menu (16 October 2026), premium AAAA flower costs $10 for a single gram, a median $30 for an eighth (3.5 g, $8.57 a gram) and a median $160 for an ounce ($5.71 a gram). Our 35 in-stock ounce deals run from $39 to $110, a median of $72 or $2.57 a gram. If you want to try a strain before committing, start with a gram or an eighth from the premium flower category; if you smoke regularly, an ounce from budget buds stored properly will stay in good shape for months.
Wherever you buy, the same check applies: fresh flower should smell strongly, feel slightly springy and show no fuzz or powder.
Frequently asked questions
How long does weed last?
About 6 to 12 months at close to full quality if stored airtight, cool and dark. After that it slowly gets weaker and harsher as THC breaks down into CBN, but clean, dry weed stays safe to use.
How old can weed be before it goes bad?
There is no fixed age. Clean, dry weed can be years old and still safe, just weaker. It goes bad when it gets moldy, which can happen at any age if it gets damp.
Is 6 month old weed still good?
Yes. If it was kept in an airtight container away from heat and light, six-month-old weed is still good and close to its original strength and flavour.
Will smoking old weed make you sick?
Old weed that is dry and free of mold will not make you sick, but it may taste harsh and feel weaker. Moldy weed is the problem: do not smoke it.
What does spoiled weed look like?
Spoiled weed has white or grey fuzz, a powdery white dusting, or black or brown spots, and usually smells musty, damp or like wet hay instead of like cannabis.
Is it bad to smoke slightly moldy weed?
Yes. Inhaling mold spores can irritate the lungs and cause allergic reactions, and the risk is higher for people with weakened immune systems. Throw it away.
Can moldy weed be saved?
No. Mold spreads further than the patches you can see, so cutting it off does not work. Throw out the whole batch and wash the container.
How do you keep weed fresh?
Store it in an airtight glass jar in a cool, dark place at roughly 55% to 62% humidity, and avoid plastic bags, heat and sunlight.
Sources: Aviram J. et al., “THC degradation does not impair the accuracy of THC doses aerosolized by the metered-dose SyqeAir inhaler: a 24-month stability trial”, Journal of Cannabis Research (2022). Gwinn K.D. et al., “Fungal and mycotoxin contaminants in cannabis and hemp flowers: implications for consumer health and directions for further research”, Frontiers in Microbiology (2023). Prices from Bud Cargo’s live in-stock catalogue, 16 October 2026.
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