KITCHENER - A Cambridge man who devoted months to growing four cannabis plants has had them stolen.

Dave Sousa says he was at work last week when his backyard was raided by an unknown person, who he says got into his backyard from an adjacent school.

Then, Sousa says, the thief climbed into an enclosure built to protect the cannabis plants and got to work. Where the six-foot plants once stood, two stalks, each with a single branch, remain.

"It's basically an invasion of privacy and having something taken from you," he says.

Footage from Sousa's backyard surveillance camera appears to show a person with their face covered climbing into the enclosure.

Once inside, branches from the cannabis plants can be seen as they're thrown over the fence.

Then the thief jumps back over the fence, packs the cannabis into a hockey or duffel bag, and leaves.

Youbin Zheng is a horticulture professor at the University of Guelph. He says that the culprit was no expert, because of how they went about gathering the plants.

He calls the stolen stems "useless" because they don't contain any cannabinoids.

And another thing: Sousa says his plants weren't ready to harvest yet.

"They weren't quite ready yet, they still had about four weeks to go, so it's kind of wasted time for him," he says.

Zheng says that cannabis plants begin to flower between the middle of August and Sept. 24, and need between seven and nine weeks to mature.

"The earliest would probably start to mature this time of the year, so the first week of October," he says.

Sousa has been legally growing the cannabis plants in his backyard since May. He also grows vegetables, like peas, peppers and tomatoes.

So why the venture into growing cannabis?

"It's totally legal now and everybody's doing it," Sousa says. "I don't know, who doesn't like a little puff here and there?"

Regional police say that, while it's difficult to determine the value of the stolen cannabis, they could be worth up to $1,000 per plant. Zheng says that plants as tall as Sousa's could be worth a street value of almost $4,000, if the goal of the person stealing was to sell it.

That might have been what made Sousa's crop so appealing to the thief.

But that's not what he's most annoyed about: he says the worst part is having a stranger targeting his backyard.

"I could be outside having a dinner with family or friends and having people jump your fence, willing to steal something off you," Sousa explains.

Sousa says the man returned the following morning before 4 a.m. to clean up the rest.

He's hoping that people will recognize the perpetrator and be able to report them to the authorities.

Police say that growing cannabis outdoors is a risk, but did say that growing plants in greenhouses and installing motion-sensor lights could deter thieves.