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How to tell if your weed is safe

Cannabis plants are at risk of numerous threats, many of which make the weed problematic for human consumption. Seedsman recently ran a series for growers (‘How to deal with common plant pathogens’), helping to identify and solve some of the most common problems during the growth and flowering stages, but here we present a guide for the consumer to enable you to quickly check whether your buds are safe or not.


Cannabis plants are vulnerable to numerous different forms of mould which can pounce to destroy crops at any time, so it helps to know the signs of danger. With grey mould and powdery mildew, try to scan the buds closely for signs of abnormal-looking fuzz, or a residue similar in appearance to baking flour. Know  the difference between mould and trichomes, the shimmering crystals which adorn buds and leaves, and produce those delightful terpenes and flavonoids. These glistening hairs are an essential component of the cannabis plant, but will appear different from mould. It’s worthwhile using a magnifying glass to help distinguish between trichomes – which will appear milky, shimmering, and mushroom-capped – and mould, which will be fuzzy, dusty-looking, and can be white, brown, green, gray or black. The smell of the weed is another quick indicator of mould – if it smells damp, or musty, reject it. Mouldy cannabis can be deadly, so take the time to inspect before use.

Grit Weed

Pathogens are one thing – an avoidable hazard which can manifest  at most any grow site – but there are some underhanded methods used to boost weight or appearance of plants, and they’re all extremely dangerous for the consumer. Some plants have been found to be laced with everything from sand and sugar, to far more troubling additives such as laundry detergent, and silica glass. Cannabis which has been manipulated in this way is often referred to as grit weed. Grit weed is typically characterised by its texture and appearance, and has the confusion of appearing to glisten much like a good cannabis.  Around ten years ago, a prominence of grit weed in parts of the United Kingdom led users to develop a quick and easy method of testing weed – rubbing it on glass. If in doubt, it’s worth taking a small bud and rubbing it across something with a glass surface (try to avoid using your Pink Floyd CDs) and if the surface appears scraped, it’s grit weed. Reject this immediately, as smoking this could cause severe and fatal complications.

Fake Weed, aka Synthetic Marijuana

Another alarming and dangerous trend is the spraying of plants with synthetic cannabinoids – mind-altering, but usually toxic, chemicals which induce a high-like feeling. You might not even know you’ve ingested these at first, as, to a novice cannabis user, the initial effects may appear similar – but the effects of these chemicals are often negative, unpredictable, and highly dangerous. Some of the more unsettling effects from fake weed include:

  • Headaches
  • Rapid heart rate
  • Raised blood pressure
  • Vomiting
  • Seizures

Synthetic cannabinoids are classed in a group called New Psychoactive Substances (NPS), and are unregulated, mind-altering chemicals designed to produce similar effects as some illegal drugs. Obvious from appearance alone, this fake weed is usually sold in small bags, in small quantities, and is recognisable as a mixture of dried leaves from various herbal plants, in various colours including, green, brown, red, or blonde. If the packaging contains a disclaimer to the effect of “Not for human consumption”, you can bet good money it’s on there for a reason. Avoid at all costs.

PGR Weed

The term Plant Growth Regulators may sound relatively innocuous, but the reality is far more sinister.  PGRs are chemicals used to alter the growth of a plant or crop in a specific manner, and have been used with a degree of prevalence in some branches of agriculture throughout the 20th century – although, now PGRs are typically highly regulated, or banned completely. In cannabis growing, they would be typically employed to grow bigger yields, with thicker, fuller, buds or bushier plants. A grower many not even know that the seemingly beneficial products they’ve used on their plants even contains PGRs, due to the astonishing fact that cultivation chemicals for cannabis are not required to list their ingredients.

PGRs such as Daminozide and Paclobutrazol are toxic, and can cause significant damage, including:

  • Nausea
  • Vomiting
  • Long-term lung damage
  • Damage to reproductive health

Fortunately, PGR weed is easily identifiable to even the untrained eye, with a vastly different appearance to normal cannabis, and can be diagnosed at a glance, looking tightly-packed with an over-abundance of orange hairs which, upon breaking open a bud, will have most likely permeated throughout . You should also observe a hard, rock-like density, buds noticeably smaller than usual, and lacking in those prized glistening trichomes. A final tell is the absence of any familiar weed smell, caused by underdeveloped terpenes.


Hopefully this article has helped shed some light on a few of the risks and ruses you may encounter, and offered some elementary detective tricks you can employ to keep yourself safe.. If it doesn’t look right, and it doesn’t smell right, then it’s not right. Resist the initial temptation to immediately grind and smoke your new stuff – make safety your top priority, and remember that ultimately, the best way to ensure safety is to grow your own product, where laws permit you to do so.

Cultivation information, and media is given for those of our clients who live in countries where cannabis cultivation is decriminalised or legal, or to those that operate within a licensed model. We encourage all readers to be aware of their local laws and to ensure they do not break them.

This post is also available in: French

Duncan Mathers