Whenever he walks along a street, Hirokazu Tsukaya loses his awareness of traffic as he becomes preoccupied with peering into such spots as the differences in levels between the sidewalk and the street or the bases of utility poles.
The reason for his preoccupation is the presence of various seasonal grasses and flowers, including dandelions, heartsease and antirrhinums that grow through cracks in concrete and asphalt.
"Without being hindered by other plants, [such grasses and flowers] can take all the sunshine for themselves. In addition, there is a high water content in the earth. That's why cracks and gaps [on the roads] in urban areas are a paradise for plants," said Tsukaya, a 49-year-old professor of the University of Tokyo.
He published a book in which he compiled details about such plants, titled "Sukima no Shokubutsu Zukan" (A picture book of plants that grow in cracks). It was released as part of the Chuko Shinsho softcover series in late March.
As a researcher of leaf genetics, Tsukaya has conducted investigations in Southeast Asia, Africa and other areas. Why has published a book about plants in urban areas?
"Weeds have gone through complicated cross-pollination many times. Sometimes I discover plants of an alien species I never expected. Cities and remote places are alike in terms of their potential for discovery," Tsukaya said.
Tsukaya began walking in cities with a camera in his hand about 10 years ago. He has taken about 1,000 photos of more than 300 plant species.
Examples of plants discovered in unusual places include a pine tree that had grown in the gutter of a house, and a weed that is native of North America found in the bed of a truck.
"Weeds grow in their own way. Why not peer in cracks [in the road] sometimes and relax?" Tsukaya suggested.