Three years ago, Mr Kruse threw up a career as a foreign exchange dealer to devote his life to promoting the virtues of hemp. Now, on the eve of his 26th birthday, he is still enthusiastic about the product, but some aspects of the trade are beginning to give him a headache.
One part of the plant he has never been never allowed to sell. Despite the suggestive labels on the face cream - "Joint" - or the generic "Cannabis" brand on the drink labels, no quantity of any of his wares can get the customers stoned. The best he can offer anyone aiming to get high are marijuana seeds and books on their cultivation.
Last Monday, the seeds had to be removed from the shelves. Under a new law the sale of seeds "intended to grow marijuana for illicit consumption" is no longer allowed.
After a drop in the Eighties, the weed is back in fashion in Germany. Mr Kruse runs one of a chain of 18 stores. There are about 450 shops supplying kits for growing marijuana. They now risk going out of business.
But that's not what worries him most. "The real problem is that the kids are not coming to the shop any more," he says. "They will have to go to the dealers at the railway station, who also sell ecstasy and heroin. The government loses tax revenue, while the Mafia gets rich."
There are an estimated 4.5 million cannabis users in Germany. Possession is illegal, but in many Lander police are told to turn a blind eye to small quantities. Short of going to the dealers or driving to Holland, the most convenient way of obtaining the stuff was to grow one's own.
Mr Kruse looks sad as he leafs through a Dutch catalogue. A packet of 10 seeds, to grow varieties such as "Holland Hop", "Buddha" and - for the connoisseur - "Skunk", used to cost between DM40 (pounds 13) and DM80.
But all is not lost, because German ingenuity has found a loophole. The new regulation bans the "sale" of the offending seeds. But can they be given away? Mr Kruse now sells CDs: rather expensive at DM40 as they only carry two reggae numbers, one called "Stoned". But the package contains 10 little seeds. "You reap as you sow," it says helpfully on the label.
Mr Kruse is not sure he will get away with this scam, but the industry has high hopes of another product. Budgies and their owners prize marijuana seeds above all others. Mr Kruse's shop has always stocked sacksfull for bird-lovers, but he plans to start selling them by the gram next month.Reuse content