Not only are they a biodiversity disaster, but the millions of sugi (cedars) planted as official policy in the postwar years to yield cheap timber -- but which are now more expensive to harvest than the cost of imports -- have become a serious health hazard across Japan.
This year, the nation's 20 million kafunsho (pollen allergy) sufferers are about to embark on a spring season of particular discontent, with the Health Ministry warning that -- thanks to last year's long hot summer -- the trees look set to release record quantities of pollen.
So what is to be done if you are one of the rising number forced to endure from now until May the nightmare of a running nose, itchy eyes and sneezing?
Well, there is a whole industry waiting to sell you drugs, face-masks, air filters and special teas. Then there's Hokkaido.
This year, the town of Kami- shihoro, in the center of the virtually cedar-free northern island, is running a pilot project it hopes will lure kafunsho victims from the pollen-polluted mainland to their pollen-free paradise.
At the end of March, participants in the inaugural "Cedar Pollen Retreat Tour" will be met at JR Obihiro Station and taken by coach an hour north to Kamishihoro. After arriving at their hotel, they will be able to relax in the fresh air and hot-spring baths, enjoy local food and natural beauty -- and also be instructed about allergies and health.
"We have had visitors from places like Osaka, who stayed at a hot-spring resort to ease their allergies," said Hideyuki Matsuoka, a Kamishihoro town official.
Prior to launching its "evacuation project," he said that the town ascertained that the area really did have a low pollen count. Hokkaido is not a natural habitat of cedars or another troublesome tree, the hinoki (Japanese cypress), though a few had been planted. However, he was pleased to report that "around Kamishihoro there are none of these trees, and we hope kafunsho sufferers will regard our town as a refuge."
It may be good business for town of Kamishihoro -- a farming community of 5,500, down from 13,600 about 50 years ago -- but immune-system experts also support the "Hokkaido remedy."
"Oh, yes -- moving to Hokkaido will help reduce symptoms of pollen allergy," said Takashi Nishimura, a professor of immunology at Hokkaido University. Nishimura has conducted research on Hokkaido University students who came from the mainland, asking them about any pollen allergies. He found that an overwhelming majority of subjects reported the severity of their symptoms had been dramatically reduced a few years after moving to Hokkaido.
"Those who have cedar-pollen allergy are more easily affected by any pollen, and in some cases they start having an allergy to the pollen of other trees in Hokkaido. But it is true that those who suffer from cedar-pollen allergy on the mainland have far fewer symptoms here, and some are completely cured," Nishimura said. "Actually, my wife is from Honshu, and she used to suffer from pollen allergy there, but now we live in Hokkaido she has no symptoms."
For its pilot project, the municipality of Kamishihoro is inviting 10 pollen-allergy sufferers from the mainland for an expenses-paid stay March 23-27 (except travel costs to Obihiro). During their vacation, they will be led on hikes, on ski or cross-country skiing trips and be given talks on the relationships between diet, health and the immune system.
"We plan to lay on programs to teach participants about the allergy scientifically -- but also ensure they have lots and lots of fun in the natural surroundings of Hokkaido," Matsuoka said. "And if it is successful, the tour will be expanded in years to come."
Sounds like a plan that's definitely not to be sniffed at by the nation's growing army of seasonal sneezers -- of who 220 have already submitted their names in hope of being selected.