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Toronto’s drug laws have been changing since the legalization of marijuana, but how police identify grow ops has not changed much. Pardons for marijuana possession allow some people to clear their criminal records. For other offences, like drug cultivation, selling to minors, and DUI offences, the sentencing for marijuana charges is more severe.

Although Toronto residents can now grow up to 4 plants (per household, not per person), there are strict regulations on the production. The plants can only be grown indoors and for personal use. Any production intended for distribution or beyond the legal limit can result in drug cultivation offences, which carry severe sentences.

In light of legal growing coexisting alongside harsh penalties for drug cultivation, we examine how police identify a grow op. As well as how they can differentiate it from legal growing.


Tips From The Public

One of the biggest sources for identifying a grow house is public information. Even grown indoors, large scale marijuana production comes with a number of telltale signs. Not all of these signs may alert the public to a house containing a grow op, but many of them are enough to elicit complaints which can put the location on police radars.

Suspicious behaviours or appearances are a common way to recognize a grow op. For instance, people coming and going at odd times of the day/night or numerous visitors showing up for short periods.

Equipment noise can result in complaints from neighbours. Producing large quantities of marijuana indoors can require significant equipment usage. With the equipment running even during the night, complaints are not uncommon. The noise is often amplified by the use of generators to hide the elevated electricity use a grow op requires.

Finally, the odour is a big indicator in helping to identify grow ops. Growing, harvesting, drying, and consuming the plants produces an unmistakable odour. Produced in large quantities, this smell is hard to hide. A sweet skunky, rotting smell constantly permeates the building. Neighbours notice the constant odour and may tip off the police.

Attempts to cover up the smell of a grow ops, like mothballs or fabric sprays can be just as overwhelming, alerting the public just as easily as the smells of drug cultivation themselves.

A public tip is unlikely to directly result in a search warrant but can alert police to monitor a location. Then they can gather enough evidence to get a warrant.

Visible Signs

The visible signs of a grow op help identify site locations by the police. The larger the operation, the more apparent these signs may become.

The windows and walls are major giveaways. Condensation, for example, builds up rapidly due to the high humidity requirements of marijuana cultivation. Mildew, mould, and rot often show up on the windows and walls.

Coverings may be placed on the windows to block sunlight and/or protect from visible signs of condensation. Plastic coverings and tightly shut blinds that never open are common signs.

Abandoned buildings are another thing to look out for. Everyone in Toronto knows the ludicrous value of real estate here, even an empty lot can sell for a small fortune – and sells fast. So there isn’t much reason to leave a place abandoned unless it’s generating revenue some other way. Grow Ops are often not lived in and so, may appear abandoned.

To disguise this, some grow houses will leave the lights, TV, and radio on at all hours of the day. They may even leave children’s toys on the lawn (even though children are never seen on the property) to make it appear lived-in. There may also be attempts to deter closer inspection, such as Beware of Dog, or Guard Dog signs. If anyone is paying attention, these sorts of distractions are just as suspicious as leaving the building abandoned.

Power Usage

Even for personal use, growing marijuana uses a noticeable increase in your power bill. A home operation can tack on an extra $10 to $80 per month, depending on where you live, how much you grow, and the equipment you use. When producing larger quantities for distribution, the power demand is far more significant.

The intense power usage by grow ops may be noticed by the power company, the neighbours or the police. Frequent outages and/or periods of dimmed lighting and reduced power in neighbouring homes can be a sign of a nearby operation.

As well, discovering electricity theft or large spikes in power are typical tipoffs that marijuana cultivation is going on.


Police tend to keep tabs on previous grow houses and locations. These grow op locations are usually known to gangs, who will reuse them often. Periodically checking in on these locations can help uncover drug cultivation.


Radios can be used to help identify the presence of grow ops and uncover their location. This is something that was initially discovered by HAM radio hobbyists, who started getting interference with their radio signals.

Now it is known that the equipment used in drug cultivation is a common source of this interference. To figure out the source of the disruption, police can use trilateralization with multiple radios. The closer the radio is to the source, the greater the disruption.

To trilateralize the location, they take a radio and make a circle on a map where the interference is strongest. Then, they do the same with radios at two different starting points. Comparing the maps, they see where the circles overlap, resulting in a good approximation of the grow ops location.

Heat Detection

Police also possess advanced equipment for detecting drug cultivation. One such device is infrared cameras. Different plants, like cannabis, emit their own specific heat signatures. With the right equipment, these signatures can even be picked up through walls. This allows police to detect marijuana without a search warrant.

This is hardly the only method police have used to monitor without a warrant. Recently Toronto police admitted to using Stingray devices to illegally intercept private communications. These devices allow them to wiretap every cellphone in a given area, both the regular public and those they are investigating.


The main differentiator between detecting illegal grow ops and legal growing is scale. Growing marijuana for personal use results in fewer obvious signs of a grow op, and the signs that are there are less noticeable. There’s no reason for legal growing to result in suspicious behaviour or cause significant disruption.

If abiding by local laws, it’s unlikely that growing 4 plants will be discovered. And if they are, you don’t have to worry about a marijuana grow op charges. Growing a larger number of plants, however, is much easier to detect, and neighbours are more likely to report the accompanying suspicious behaviour.


If you find yourself charged with drug offences you should consider experienced counsel to assist you. William Jaksa is a Toronto Criminal Defence Lawyer with experience challenging search warrants and wiretap warrants.

Contact William Jaksa today for a consultation.

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