Fall street-sweeping has launched in Minneapolis and St. Paul — leaves optional.

During an autumn in which phenologists say that leaves are a week or more behind in parting from twigs, the state’s two biggest cities say they can’t wait for them to fall if they’re to finish before the first snowfall.

“Years ago, we used to agonize, watching the trees,” said Mike Kennedy, street maintenance supervisor in Minneapolis.

But with public demands for knowing the street sweeping schedule in advance, he said, the sweep dates are usually set in September, long before knowing the timing of an autumn such as this one. That allows the city’s council members to put the information in newsletters and the city to load a website where residents can look up their block’s sweep.

Minneapolis started sweeping a week ago, while St. Paul began Thursday. With 871 miles to sweep in St. Paul and about 1,100 in Minneapolis, the cities say they need to start now to finish in time.

That’s unlike many suburbs. Woodbury does its sweeping in September. Others, such as Richfield, sweep multiple times; Plymouth targets only areas near lakes.

Chris Buyarski, a University of Minnesota scientist, said the delay in leaf fall could be two weeks, possibly because a late spring featured an early May snowfall. Freezing temperatures that promote leaf drop also held off later this year, he said.

So why not hold off until the leaves are down? Sweeping takes 16 working days in St. Paul. The goal in Minneapolis typically is to finish by the Friday before Thanksgiving.

“It’s kind of our dangerous time,” Kennedy said, calling the trade-off between waiting for leaves and beating snow “our squeeze play.” Minneapolis and St. Paul differ from some of their outer suburbs in that each features a canopy of boulevard trees likely to shed a substantial amount of their leaves onto the street.

Jeannine Clancy, Golden Valley’s public works director, said that the late leaf fall so far has meant reduced volume at the park where residents may drop off leaves for composting by a contractor.

Cities sweep streets in the fall for debris and grit that accumulate after their spring sweep, but also because they feel obligated by the state to do so under their stormwater plans to reduce leaf-borne pollutants entering waters. But Scott Fox, a hydrologist for the Minnesota Pollution Control Agency, said there’s no specific requirement for sweeping streets, although the state offers guidance on sweeping benefits and techniques.


Twitter: @brandtstrib