Photo/IllutrationA combination of cherry blossoms and rapeseed flowers heralds spring in Fukuoka. (The Asahi Shimbun)

“Nanohana” (rapeseed flowers) have fascinated many people, and poet Bocho Yamamura (1884-1924) was no exception.

In a mantra-like piece, the only words he used, repeating three times, were “ichimen no nanohaha” (rapeseed flowers all over the place).

When dense clusters of these little flowers dye the fields and meadows yellow, the arrival of spring is felt wherever one may be.

Land ministry official Masami Osugi, 53, is overseeing an experiment to reduce rapeseed plants on the banks of the Uzumagawa river in southern Tochigi Prefecture.

“Most flowers growing in the wild today are of the variety known as ‘seiyo-aburana’ (Brassica napus),” he said. “Their vigorous proliferation is harming the embankments and levees where they take root.”

The roots of this non-native species are as thick as daikon radishes. When the roots wither and die, they become infested with micro-organisms and earthworms, which invite moles to make their nests.

Too many nests lower the embankment’s ability to retain water.

“To prevent the embankment from collapsing and causing flooding, we are trying to figure out, by trial and error, when and how we should cut back the rapeseeds,” Osugi said.

His experiment, now in its third year, is clearing a 3-kilometer section of rapeseed growth on one side of the sloping embankment.

Osugi has determined that this has reduced the blossoms, stunted the growth of stems and made their roots skinnier.

Walking on the slope where the plants had just been cut back, I noticed gaping black holes here and there. When I stuck an arm in one, I found the hole branched out in all directions. The soil around the holes was fluffy.

You could easily end up shin-deep in one if you don’t watch your step.

A haiku poem by Fusei Tomiyasu (1885-1979) goes to the effect, “Loving the mundane that's nanohana.”

I now know that rapeseed can be a menace to the maintenance of embankments and levees, but the sight of its yellow waves swaying in the river breeze still fascinates me.

In spring, it’s too sad not to see “rapeseed flowers all over the place.”

--The Asahi Shimbun, April 5

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Vox Populi, Vox Dei is a popular daily column that takes up a wide range of topics, including culture, arts and social trends and developments. Written by veteran Asahi Shimbun writers, the column provides useful perspectives on and insights into contemporary Japan and its culture.