Cannabis farms - spotting the signs

Alert message sent 27/01/2021 17:31:00

Information sent on behalf of Wiltshire Police

The phrase cannabis farm may conjure up images of fields of hemp blowing in the open air. 

But in reality they are usually in dingy, dirty, cramped houses packed full of cannabis plants being grown under hot, bright lights.  Ordinary homes almost decimated to accommodate criminal groups' activities to grow the illegal Class B drug and then sell it on. 

Between July 2020 and January 2021 we discovered 10 cannabis so-called farms or factories in Swindon.  

Insp Carly Nesbitt said:  "These so-called farms cause no end of problems for the community from where they operate. 
"Often, vulnerable victims of human trafficking and modern slavery (often illegal immigrants) are forced to act as caretakers for the farms or factories - being forced to stay in uninhabitable conditions to look after the plants and machinery. 
"This Illegal drug activity not only affects our wider communities, but, in particular, those vulnerable individuals within society who are often forced, coerced or exploited into carrying out this illegal activity on the behalf of organised gangs.
"The drugs support a wider drug network which cause many issues for local neighbourhoods. 
"It does appears that the number of farms are on the increase in Swindon and with that we would like to remind members of the public to be on the look out for any suspicious activity in your street or local community.  
"This work comes under the Project Optimise banner, which is  the force’s approach to serious and organised crime, which can range from drugs and violence, to burglary and money laundering.  These farms are part of that.
"We, along with the public's help through information, can target and close down these farms." 

How can you spot a cannabis farm in your street? 

Here are the signs to look out for:

Windows permanently covered
Do you know of a house nearby where the curtains are drawn all day long? Are the windows blacked out with panelling or sheeting?  Are there chinks of bright light showing from the edges of the window covering?  Is there something they don’t want you to see?  This could be a sign that there are bright artificial lights (required for cultivation) glowing inside, often coming on during the night on a timer. Young plants need around 12 hours of artificial light each day. Do the lights turn on and off at exactly the same times each day? Sometimes the room at the front of the house is left open and ‘set up’ to give the pretence of normality.

High levels of condensation
Are the windows always misted up? The condensation may well be due to inside having been turned into a makeshift greenhouse.  For the best plant growth, cannabis needs an atmosphere similar to a greenhouse and this can cause a lot of condensation.

Sense of smell
A cannabis crop takes about three months to produce. The young plants have a faint smell, which may not reach the exterior of the house, but during the final four weeks the flowers/buds start to grow and the plants will smell intensely. It is a distinctive sweet, sickly aroma.

Lots of visitors
In some cases there will be a person living at the house to look after the grow. If they are ‘living-in’ permanently, they will barely be seen. If they are tending to more than one site they will come, tend to the plants and leave again, often in the early hours or at night. They won’t be sociable neighbours, they will want to keep a low profile. They will be worried about security, as this crop is valuable.
Do the visitors come and go frequently, often staying for short periods of time and at odd hours of the day? Are there new faces/vehicles turning up each time? Do they have large amounts of rubbish, including compost bags? Have you seen equipment being moved into the house (cannabis grows require significant amounts of ventilation and lighting)?
If you think there may be a cannabis farm, are you able to note visitors vehicle registration numbers without alerting them to your suspicions?

Rocketing electricity bills
The lights, dehumidifiers, hydroponic systems and heaters take a lot of electricity. Many farms have been found where drugs gangs have hacked into the electricity wires before the meter to that individual house and so bypassed having to pay for the electricity. This can increase fire hazard risks.
If you are a landlord who gets a copy of the bill, has it dropped or gone up suddenly? If so, your neighbourhood growers could have tapped into your supply and are charging you to power their drug operation. You should contact your supplier and the police immediately.

What happens when it snows?
Cannabis factories produce a lot of heat, which can cause tell-tale signs, especially in winter. When it snows, the roofs of cannabis farms can be obvious as the snow melts quickly, meaning it is probably the only house on the street without a snow-covered roof.
Similarly, do birds gather on the roof in cold weather, taking advantage of the heat that is being emitted?

Constant buzz of ventilation
If you can hear the constant noise of a fan, at all times of the day or night, chances are it could be acting as ventilation for the cannabis grow.

If you suspect there is a cannabis factory next door, you should phone us on 101 or 999 if a crime is in progress.  You can also contact Crimestoppers on 0800 555111 or go to
Message sent by
Mark Jones (Police, Media Officer, Wiltshire)

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