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What weed shouldn’t smell like

Published on December 24, 2019 · Last updated September 16, 2022
(Steven Senne/AP)

Take a quick look through any of Leafly’s strain pages, and you’ll find plenty of descriptive terms for the cannabis plant’s aromas.

People compare particular strains to a variety of scents: lemon, pine, cloves, wood, skunk, and even diesel. There are many things cannabis can smell like, but do any of them indicate a whiff of trouble?

Here are the most common olfactory clues that something’s wrong with your cannabis:

It smells like freshly-cut grass

The scent of freshly-cut grass is an indicator that the chlorophyll in cannabis is decomposing into ammonia. This problem originates during the curing process, and it’s an indicator of incomplete curing.

Curing is an additional step in the cannabis preservation process, after drying and before consumption. Curing cannabis properly allows it to mature into a form that can maintain its freshness for up to two years. Rushing this process, or completing it incorrectly, can result in cannabis that smells like lawn cuttings.

Curing is sort of like aging wine or cheese. Some cannabis growers insist that long cures improve the flavor of the final product.

The cannabis drying and curing process can be delicate. It requires a controlled environment, with specific temperature, humidity, and air circulation levels. The initial drying phase takes place around room temperature, at 40-50% humidity, with plenty of air circulation.

The ultimate guide to drying and curing cannabis for the best results

After initial drying, the cannabis is trimmed and separated into flowers. It is then stored in an airtight container in a cool, dark place until the buds have rehydrated slightly. Initial drying forces the moisture into the center of the plant, but a slow cure in a sealed jar forces the moisture to distribute itself more evenly, contributing to the metabolism of sugars, starches, and nutrients. A proper cure ensures that cannabis stays good for up to two years.

Importantly, the container must be “burped” regularly while curing in order to replenish the oxygen in the container. When curing is still incomplete, the cannabis will smell like freshly-cut grass or lawn clippings when it is opened for burping. However, once the process is complete, it will begin to smell like cannabis again.

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If you receive cannabis that has an ammonia or a freshly-cut grass smell, this is an indicator that something went wrong during the drying or curing process. Most likely, the cannabis has not cured completely.

Incompletely cured cannabis will taste harsh, and this harshness is likely due to the ammonia. There is also some evidence suggesting it might even pose a health risk. A 2008 study of illicit cannabis in the UK found the presence of ammonia at toxic levels.

It smells like mold or mildew

Another bad odor to look out for is mold or mildew. If your cannabis smells like a wet towel, this might indicate contamination with mold.

How to Prevent Mold on Cannabis While Curing

Mold contamination happens when the plant is grown or stored in humid conditions that allow mold to grow. Typically, this occurs during the growing phase, but it can also happen after harvest, if a plant is dried incorrectly. Once cannabis has been dried and cured, mold contamination is unlikely unless the cannabis gets wet.

You can also examine the appearance of the cannabis to determine if it’s moldy.

Unfortunately, some molds can mimic the appearance of trichomes (crystals) to the untrained eye.

A good rule of thumb is: if anything seems off about your cannabis, it’s best not to consume it.

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Laura Tennant
Laura Tennant
Laura Tennant is a Toronto freelance science writer. She has an Honours B.Sc. in Neuroscience from the University of Toronto. She hopes her writing will help others make better-informed choices about their health and lifestyle.
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