In an effort to recruit ordinary citizens to help uncover illegal marijuana crops, Dutch authorities are mailing scented green cards that implore ordinary citizens to "assist in combatting cannabis plantations". What exactly is the plan? Here, a brief guide:

What are Dutch authorities doing exactly?
They have sent 8-by-4-inch cards to 30,000 households in Rotterdam and The Hague, urging citizens to do their part in the fight against urban marijuana growers. The cards have two boxes that, when scratched, emit a cannabis smell to help citizens know what to sniff for. The cards also list signs citizens can look for, such as closed curtains and the sound of ventilators, and a number to call to report anything suspicious. "Citizens must be alerted to the dangers they face as a result of these plantations," says a spokesperson for a government-appointed group fighting marijuana cultivation.

Isn't the Netherlands a land of marijuana freedom?
Not quite. Cannabis is technically illegal there, but under a 1976 "tolerance" policy the consumption and possession of a small amount — up to 5 grams — was decriminalized. About 6,000 marijuana-growing operations are busted every year, and according to some estimates there are as many as 40,000 illegal plantations across the country.

Why the sudden crackdown?
The scratch-and-sniff cards are backed by Stedin, an energy company. Illegal cultivation is a big concern for power companies because many marijuana plantations illegally siphon off both water and electricity, which is needed to power the large lights needed to grow plants indoors. This can lead to short circuits and a high risk of fire. "Cannabis cultivation has to stop," a police statement reads. "It might seem innocent, but it's not."

Sources: BBC News, The Telegraph, The Washington Post, The Huffington Post, AFP