Does Weed Have to Be in a Bag? How to Store It Properly

No, weed does not have to be in a bag. For keeping it fresh, a bag is rarely the best choice. What works best is an airtight glass jar, kept somewhere dark and cool, with the buds at a steady, moderate humidity. A good bag can do the job for a short time or for carrying a small amount. A thin sandwich bag in a sunny spot is about the worst place your buds can sit.

Why that is comes down to what breaks cannabis down: light, air, heat and the wrong amount of moisture. Here is what each one does, and how to store your weed so it still smells and smokes the way it should weeks later.

What makes stored weed go bad

Light

Light does the most damage. In one 1976 storage study, researchers kept cannabis samples and solutions under different conditions and found that exposure to light (not even direct sunlight) was the greatest single factor in the loss of cannabinoids (Fairbairn et al., 1976). A clear bag or jar on a windowsill is exactly what you want to avoid.

Air

Oxygen is the next problem. The same study found that air oxidation led to significant losses of cannabinoids, and that THC broken down by air in the dark turns into CBN, a different cannabinoid. So old weed is not just weaker in THC; part of it has turned into something else. The researchers also noted that losses were smaller when the resin glands on the plant were left undamaged, because the glands themselves work like small sealed containers. In plain terms: handle your buds gently, and do not grind them until you are about to use them.

Heat and time

A four-year study by researchers in Venice and Padua, Italy, stored cannabis and hashish in two ways: in the light at room temperature (22°C), and in darkness at minus 20°C. THC broke down and CBN formed under both conditions. Temperature changed how fast that happened, while light changed both the speed and the way THC was converted (Zamengo et al., 2019). So cool storage slows things down, but nothing stops the clock completely. In practice, the sooner you use it after a proper cure, the closer it stays to how it started.

The 1976 study found that temperatures up to about 20°C made little difference, and it concluded that carefully prepared cannabis is reasonably stable for 1 to 2 years if stored in the dark at room temperature, though it still slowly loses potency. In practice that means a normal cupboard is fine. A spot next to a radiator, a stove or in a hot car is not.

Moisture

Too wet and buds can grow mold. Too dry and they crumble, turn harsh and lose their smell. ASTM International, which writes technical standards for many industries, publishes a standard for storing dried cannabis flower. It sets a water activity range of 0.55 to 0.65: below 0.65 to guard against the growth of microorganisms such as mold, and above 0.55 to avoid the buds breaking in normal handling and storage (ASTM D8197-22, page last updated November 3, 2022).

Water activity is measured on a scale from 0 to 1, and in a sealed container it matches the relative humidity of the air inside it divided by 100. So the range above is the same as buds sitting in balance with air at 55 to 65% relative humidity. A small hygrometer in the jar tells you where you are.

If your weed smells like hay, wet cardboard or anything musty, or you see white or grey fuzz, do not smoke it. Moldy cannabis can make you ill, so throw it out.

Bags compared

Since the question is about bags, here is how the common types hold up against those four problems. For more on keeping the smell in, see our guide to odor-proof cannabis storage.

1. Ziploc bags

• Good: cheap, easy to find, fine for a day or two.
• Bad: thin plastic is not airtight over time, lets light straight through, and squashes the buds in a pocket or bag. Not for storage.

2. Mylar bags

• Good: block light, hold smell much better than thin plastic, and many are resealable.
• Bad: you cannot see inside, and the buds get pressed together when the bag is folded or stacked. Add a humidity pack if the weed will stay in there for longer.

3. Vacuum-sealed bags

• Good: remove most of the air, so less oxidation, and they take little space.
• Bad: the bag pulls tight around the buds and can crush them and damage the resin glands. Once you open it, the seal is gone. Better for a larger amount you will not touch for a while than for a stash you dip into every day.

Better than a bag: glass jars and other containers

1. Glass jars with airtight lids

This is what we would pick. Glass does not give off smells or flavors, a good rubber seal keeps air out, and the buds keep their shape. Clear glass lets light in, so either use amber or UV-blocking glass, or keep the jar in a dark cupboard. Fill the jar loosely, not packed to the lid. Mason jars work fine.

If you cure your harvest in jars, the cure jar can simply become your storage jar. Our post on how long it takes to cure weed explains that step, and the guide from harvesting to the jar covers drying and trimming before it.

2. Rigid vacuum containers

Hard containers with a pump lid remove air without squeezing the buds the way a soft vacuum bag does. Good for bulk storage.

3. Humidity packs (Boveda or Integra Boost)

Two-way humidity packs release or absorb moisture to hold the air in a container at a set level. Choose a pack rated inside the 55 to 65% range from the ASTM standard above, and replace it when the maker says it is used up. Brand does not matter much. What matters is the rating.

4. Opaque airtight containers

Metal or dark plastic boxes with a good seal block light and air and are handy for travel. Some have a built-in hygrometer or a smell-proof seal.

Storage habits that make a difference

• Keep it dark. A cupboard or drawer, not a windowsill or shelf in the sun.
• Keep it at room temperature or a bit below, away from heaters, stoves and cars in the sun.
• Do not grind ahead. Whole buds keep their resin glands intact. Grind what you need, when you need it.
• Do not pack the jar tight. Squashed buds lose trichomes and stick together.
• Open the jar only when you need to. Each time lets in fresh air and changes the humidity.
• Label and rotate. Write the strain and the date on each jar and use the oldest first.

Storage keeps what is already there. It will not make a poor harvest better. The smell you open the jar for comes mostly from terpenes. Read more about the role of terpenes in cannabis.

What about carrying it?

For a small amount on the go, a sealed bag or a small hard container is fine for a day. For anything longer, put it back in the jar. Whether you may carry cannabis at all, and how much, depends entirely on where you are. The rules differ from country to country and sometimes from city to city, and they change. Check the current local law before you leave the house with it.

Our view

All the strains we sell have been grown by us at least once, and the people behind AMS include growers with close to 40 years of experience. From that side, our view is simple: a good harvest takes months of work, and it is a waste to let it fade in a sandwich bag in a sunny drawer. A jar, a dark cupboard and a humidity pack cost very little next to that.