You found a stash you forgot about. Maybe it’s been sitting in a drawer for six months, maybe longer. The question hits immediately: is this still good? Does weed actually go bad?

It’s one of the most common questions cannabis users ask — and the answer is more nuanced than a simple yes or no. Cannabis doesn’t spoil the way milk or bread does. There’s no hard expiry date stamped on the bottom of a jar. But over time, the compounds that make cannabis worth using — THC, CBD, terpenes — do degrade. The result is weed that’s weaker, harsher, and far less enjoyable than when you first bought it.

Then there’s mould. Poorly stored cannabis can develop mould and bacteria, and that’s where old weed crosses from “disappointing” into genuinely risky.

This guide covers everything you need to know: how long every type of cannabis product actually lasts, what the signs of degraded or bad cannabis look like, why it degrades the way it does, and how to store your weed properly so it stays as fresh and potent as the day you bought it.

At The Purple Leaf — London Ontario’s premier cannabis dispensary and delivery service — freshness is something we take seriously. Every product we carry is sourced from quality growers and stocked with proper inventory rotation, so you’re never getting stale product off our shelves.

Does Weed Go Bad? The Short Science

Weed doesn’t go bad the way food does — there’s no single moment it “turns.” What happens instead is a slow, continuous degradation of the compounds that give cannabis its effects, flavour, and aroma.

How THC Degrades Over Time

THC (tetrahydrocannabinol) — the primary psychoactive compound in cannabis — is chemically unstable. When exposed to light, heat, oxygen, and excess humidity, THC begins converting into CBN (cannabinol), a mildly sedative compound with very little psychoactive effect. This is why old weed tends to produce a heavy, sleepy feeling rather than the clear, energetic, or euphoric effects of fresh flower.

Research on cannabis degradation has produced the following well-cited benchmarks for THC loss under imperfect storage conditions:

• After 1 year: THC decreases by approximately 16.6%
• After 2 years: THC decreases by approximately 26.8%
• After 3 years: THC decreases by approximately 34.5%
• After 4 years: THC decreases by approximately 41.4%

This means a strain you bought at 24% THC could effectively be performing at around 20% after a year of mediocre storage — and closer to 14% after four years.

How Terpenes Degrade

Terpenes — the aromatic compounds responsible for cannabis’s distinctive smells and flavours, and a significant contributor to its effects through the entourage effect — are even more volatile than cannabinoids. They begin evaporating almost immediately when cannabis is exposed to air, light, and heat. This is why old weed often loses its rich, complex aroma first, long before its THC content has meaningfully dropped. When terpenes are gone, so is much of the nuance in how a strain feels and tastes.

When Does Weed Become Unsafe?

The only scenario where old cannabis becomes a genuine health concern is mould. Cannabis that has been exposed to excess moisture can develop mould and bacteria on the bud surface. Consuming mouldy cannabis — particularly by smoking or vaping it — can cause respiratory irritation, nausea, vomiting, and in people with weakened immune systems, serious respiratory illness.

The good news: mould requires moisture. If your cannabis has been kept reasonably dry, the worst case scenario is that it’s stale, harsh, and disappointingly weak — not dangerous.

How Long Does Each Type of Cannabis Last?

Different cannabis products degrade at very different rates. Here’s a full breakdown:

Cannabis Flower

Properly stored: 6 months to 1 year at peak freshness; usable for up to 18–24 months with declining potency

Fresh cannabis flower is at its best within the first six months after purchase. After that, terpene content begins to noticeably drop and THC starts converting to CBN. With excellent storage conditions (airtight glass jar, correct humidity, cool dark location), flower can remain at acceptable quality for up to 18 months. Beyond two years, most flower will be significantly degraded in both effect and flavour.

The quality of the initial cure matters enormously here. Well-cured flower from a quality grower — like the AA to AAAA strains carried at The Purple Leaf — will outlast poorly cured flower by months, simply because the moisture content was properly managed before it ever reached your hands.

Pre-Rolls

Properly stored: 3–6 months

Pre-rolls are more vulnerable than loose flower because the grinding process increases the surface area of the cannabis, exposing more of it to oxygen. They also can’t be sealed as tightly as whole buds in a jar. For best results, consume pre-rolls within a few months of purchase and store them upright in an airtight tube or container.

Cannabis Concentrates (Shatter, Wax, Crumble, Budder)

Properly stored: 6 months to 2 years

Concentrates contain very little plant material, which means there’s less organic matter to degrade or develop mould. The primary concern with concentrates is maintaining their texture and potency. Shatter, wax, crumble, and budder should be stored in silicone or glass containers, in a cool dark place, away from heat. Heat is the main enemy of concentrates — it will cause shatter to soften and lose its texture, and will accelerate terpene loss in all wax products. Stored correctly, most concentrates retain good potency for 6–12 months and remain usable for up to 2 years.

Live Resin and Hash Rosin

Properly stored: 3–6 months refrigerated for peak quality; up to 1 year in cool, dark conditions

Live resin and hash rosin are more terpene-rich than most concentrates, which also means their terpenes degrade faster. For best results, store these products in the refrigerator in an airtight, opaque glass or silicone container. Avoid opening them repeatedly — each time air enters, terpenes escape.

Hash

Properly stored: Up to 18 months

Hash contains more plant material than refined concentrates, putting its shelf life closer to flower than to wax. Keep it wrapped in parchment paper inside an airtight container, in a cool, dark place. Well-made hash can retain quality for over a year under good conditions.

Vape Pens and Cartridges

Properly stored: 6–12 months; best used within 6 months

Vape cartridges can experience two forms of degradation: the oil inside oxidizes and loses potency over time, and the hardware (battery connections, coil) can degrade and clog. For best results, store cartridges upright in a cool, dark drawer and avoid extreme temperature fluctuations. Most cartridges are best consumed within 6 months of purchase for peak effect. Disposable vape pens follow the same principle — use within 6–12 months.

Cannabis Edibles

Shelf life varies widely by product type

Edibles are unique because their shelf life is governed more by their food ingredients than by their cannabis content. Perishable homemade edibles (brownies, cookies, infused butter) can go bad in as little as 2–3 days at room temperature, or 1–2 weeks refrigerated. Commercially packaged dispensary edibles contain preservatives that extend shelf life and will carry a printed best-before date — always check this.

• Gummies and candy: 6–9 months if stored properly in a cool, dry place
• Chocolate edibles: 6–12 months sealed; store away from heat to prevent melting and bloom
• Baked goods (packaged): Follow the printed date; typically 1–3 months
• Cannabis drinks: Follow printed date; typically treat as any other bottled beverage
• Capsules and oils: 1–2 years in a cool, dark location

CBD Oils and Tinctures

Properly stored: 1–2 years (alcohol-based tinctures can last up to 10 years)

CBD oils and tinctures have one of the longest shelf lives of any cannabis product, particularly when stored in dark glass bottles away from light and heat. Oil-based tinctures typically last 1–2 years. Alcohol-based tinctures (less common) can last significantly longer. Always store them with the cap tightly sealed and keep them out of direct sunlight.

Cannabis Topicals (Creams, Balms, Salves)

Properly stored: Up to 2 years

Cannabis topicals degrade along with their carrier ingredients — the oils, butters, and creams that make up the base. Most commercially produced topicals carry a printed expiry date and last up to 2 years when stored sealed and away from heat. Always reseal after each use.

Cannabis Shelf Life at a Glance

5 Signs Your Weed Has Gone Bad

Before you light up that forgotten stash, run through this quick five-point check:

1. It Smells Like Hay, Mildew, or Nothing at All

Fresh cannabis has a rich, complex, distinctive aroma — earthy, skunky, citrusy, piney, or floral depending on the strain. When weed goes stale, terpenes evaporate and the smell fades to a dry, hay-like, or flat odour. If it smells musty, mouldy, or like a damp basement, that’s a serious warning sign and the weed should be discarded.

2. It Crumbles to Dust When You Touch It

Quality cannabis should have a slight stickiness and spring back slightly when you gently squeeze a bud. If your flower crumbles into dry powder at the slightest touch, its terpenes and cannabinoids have significantly degraded. It’s not dangerous, but it will smoke harshly and deliver much weaker effects than fresh flower.

3. It’s Spongey or Feels Damp

The opposite problem — weed that feels overly moist and spongy — suggests excess humidity exposure and is a red flag for mould. Don’t consume it until you’ve inspected it carefully.

4. You Can See White, Grey, or Black Fuzz

This is mould, and it’s the one firm “do not consume” indicator. Mould on cannabis can look similar to trichomes (the crystal-like structures on fresh flower) but trichomes are shiny and structured, while mould is fuzzy, powdery, and often appears in patches. If in doubt, toss it out. The health risk of inhaling mould spores — particularly for those with respiratory conditions or weakened immune systems — is not worth it.

5. The Colour Has Gone Brown or Yellow

Fresh cannabis is typically a vibrant green, sometimes with purple, orange, or white highlights depending on the strain. When cannabis degrades significantly, it tends to dull to a brownish or yellowish colour. Some fading is normal with age, but a noticeably brown or yellowed bud is a sign of advanced degradation.

 

How to Store Weed Properly: The Complete Guide

Good storage is the single most effective thing you can do to extend the freshness and potency of your cannabis. Here’s how to do it right.

Use Airtight Glass Jars

The best container for cannabis is an airtight glass jar — specifically a mason jar or a purpose-built cannabis storage jar with a rubber-sealed lid. Glass doesn’t carry a static charge (unlike plastic) and won’t leach chemicals into your flower. The airtight seal limits oxygen exposure, which is the primary driver of THC degradation.

Avoid plastic bags, plastic containers, and metal tins for long-term storage. Plastic generates static that pulls trichomes off the flower surface, directly reducing potency. Metal tins allow too much oxygen exchange. Zip-lock bags are fine for a day or two, but not for anything longer than that.

Control Humidity: Target 59–63% Relative Humidity (RH)

Humidity is the most precise storage variable. Too much moisture (above 65% RH) encourages mould. Too little (below 55% RH) causes terpenes and cannabinoids to dry out and degrade faster.

The sweet spot for cannabis storage is 59–63% relative humidity. The easiest way to maintain this is by dropping a two-way humidity control pack (such as a Boveda or Integra Boost pack) into your storage jar. These packs actively add or remove moisture to maintain your target RH — they’re inexpensive, widely available, and one of the most impactful storage investments you can make.

Keep It Cool: 15–21°C (60–70°F)

Heat accelerates the degradation of both cannabinoids and terpenes. The ideal storage temperature for cannabis flower is between 15–21°C (60–70°F) — cool enough to slow degradation, but not so cold that you risk condensation or trichome brittleness.

A cool, dark drawer or cupboard away from the kitchen (where temperatures fluctuate) is ideal. Avoid storing cannabis near appliances that generate heat, on sunny windowsills, or anywhere that gets warm.

Block Out Light

UV rays are one of the fastest-acting degrading forces on cannabis. Studies have shown that light exposure causes more rapid THC breakdown than almost any other environmental factor. Store your jars in a dark location — inside a cupboard or drawer — or use opaque or UV-blocking glass jars.

Never leave cannabis on a sunny countertop, car dashboard, or anywhere exposed to direct sunlight.

Don’t Freeze It

While cold temperatures slow degradation, the freezer is not recommended for cannabis flower. Freezing temperatures cause trichomes — the resin glands that contain your cannabinoids and terpenes — to become brittle and break off when the jar is handled. Freezing also introduces the risk of moisture and condensation when you take the jar in and out of the cold. The fridge isn’t ideal either, for similar humidity-related reasons.

Exception: concentrates (particularly shatter and live resin) can benefit from refrigerator storage in an airtight container, as long as you allow them to reach room temperature before opening.

Fill Your Jars Appropriately

The more air inside your storage jar, the more oxygen is in contact with your cannabis. Try to store cannabis in containers that are roughly 75% full. If you have a small amount left, transfer it to a smaller jar rather than leaving it rattling around in a half-empty container.

Store Products Separately

Keep flower, concentrates, edibles, and topicals in separate containers. Different products have different optimal humidity levels and storage conditions, and storing them together can cause flavour cross-contamination and inconsistent moisture levels.

What to Do With Old Weed

If you have cannabis that has gone stale but isn’t mouldy, it’s not necessarily a write-off. Here’s what you can do with it:

Make edibles or infused oil: Decarboxylating old flower (baking it at a low temperature to activate the cannabinoids) and infusing it into butter or coconut oil is an excellent way to make use of stale weed. The cooking process activates whatever THC remains, making it useful in homemade edibles even if it’s too harsh or weak to smoke enjoyably.

Infuse into a topical: Cannabinoids in degraded flower can still provide localized relief when infused into a carrier oil and applied topically. You won’t get high from topicals, but the remaining CBD and CBG can offer anti-inflammatory benefits.

Make a tincture: Similarly, old flower can be infused into high-proof alcohol to create a simple tincture. Even with reduced potency, it can be a useful way to consume the remaining cannabinoids without the harshness of smoking stale bud.

Rehydrate slightly dry flower: If your cannabis is just a bit too dry but not mouldy, you can rehydrate it by placing a small, fresh piece of citrus peel or a two-way humidity pack in the sealed jar for 24–48 hours. Monitor it closely to avoid overshooting into mould territory.

Buying Fresh Cannabis in London, Ontario

The best way to avoid old, degraded cannabis is to buy from a trusted source with regular inventory turnover. At The Purple Leaf, we stock cannabis flower across all quality grades from AA to AAAA, with consistent restocking to ensure freshness. Our team can help you choose the right quantity for your needs — so you’re not buying more than you’ll use before it degrades.

We offer:

• In-store shopping at our London, ON location
• Same-day local delivery in London and surrounding areas
• Canada-wide shipping for online orders

Browse our full selection of fresh flower, concentrates, edibles, vapes, CBD oils, and topicals at thepurple-leaf.com.

Frequently Asked Questions (FAQ)

Does weed actually go bad?

Yes, but not like food. Cannabis doesn’t rot or become toxic with age. Instead, its cannabinoids (THC, CBD) and terpenes degrade over time, resulting in weaker effects, reduced flavour, and a harsher smoke. The only scenario where cannabis becomes genuinely unsafe is if it develops mould — which happens when it’s stored in overly humid conditions.

How long does weed stay good?

Properly stored cannabis flower stays fresh and potent for 6 to 12 months, and can remain usable for up to 18–24 months with declining potency. Other products vary: edibles follow food expiry rules, vape cartridges are best within 6–12 months, concentrates can last up to 2 years, and CBD oils can last 1–2 years with proper storage.

How do you know if weed has gone bad?

The five main signs are: a stale hay-like or musty smell (or no smell at all), a dry crumbly texture that falls apart when touched, a spongey or damp feel that suggests mould, visible white/grey/black fuzz on the buds, and a noticeably brown or yellowed colour. If you see visible mould, discard the cannabis immediately.

Does old weed lose its potency?

Yes. THC gradually converts to CBN (cannabinol) as cannabis ages and is exposed to light, heat, and oxygen. Research shows cannabis loses approximately 16% of its THC after one year, 27% after two years, and over 40% after four years under suboptimal storage conditions. Old weed isn’t dangerous if mould-free, but it will deliver noticeably weaker and more sedating effects.

What is the best way to store weed?

Store cannabis in an airtight glass jar (like a mason jar) in a cool, dark location at 15–21°C. Maintain a relative humidity of 59–63% using two-way humidity control packs. Keep it away from light, heat, and oxygen. Avoid plastic bags, metal tins, the freezer, and the refrigerator for flower storage.

Can you store weed in the freezer?

This is not recommended for cannabis flower. Freezing temperatures make trichomes — the resin glands that contain cannabinoids and terpenes — brittle. When the jar is handled, trichomes break off and potency is lost. Freezing also risks moisture exposure through condensation. For concentrates like shatter or live resin, refrigerator storage in an airtight container is acceptable.

How long do cannabis edibles last?

It depends on the type. Homemade baked edibles last 2–3 days at room temperature or 1–2 weeks refrigerated. Commercially packaged edibles carry a printed best-before date — typically 1–3 months for baked goods and 6–9 months for gummies and candies. Cannabis capsules and oils last 1–2 years properly stored.

How long do concentrates last?

Cannabis concentrates like shatter, wax, crumble, and budder can retain good potency for 6–12 months and remain usable for up to 2 years in proper storage. Live resin and hash rosin are more terpene-rich and degrade faster — best used within 3–6 months for peak quality. Store all concentrates in silicone or glass containers, in a cool, dark place.

How long do vape cartridges last?

Vape cartridges are best used within 6 months of purchase for optimal flavour and potency. Most remain usable for up to 12 months when stored upright in a cool, dark location. Beyond that, the oil may oxidize, crystallize, or thicken, and the hardware can degrade. Avoid exposing cartridges to heat or extreme temperature changes.

Can you smoke weed that has been sitting for a year?

Yes, if it shows no signs of mould and has been stored reasonably well. A year-old cannabis flower stored in an airtight container in a cool, dark location will have lost some potency and aroma, but it is safe to consume. Expect weaker effects than fresh flower and potentially a harsher smoke due to terpene loss. If it smells musty or shows any white fuzz, discard it.

Where can I buy fresh cannabis in London, Ontario?

The Purple Leaf in London, Ontario stocks fresh cannabis flower across all quality grades (AA to AAAA), along with concentrates, edibles, vapes, CBD products, and topicals. Shop in-store, order same-day local delivery, or place an online order for shipping across Canada at thepurple-leaf.com.

Published by The Purple Leaf — London Ontario’s Local Cannabis Dispensary. Serving London, ON and shipping across Canada. Visit us at thepurple-leaf.com or call 519-777-9498.