What's up with leaves coming down so late this year?

GREEN BAY - It’s last call for leaf collection. 

Somebody might want to tell the trees.

Doug Hartman’s birch still doesn’t have a clue it’s mid-November, traditionally the time of year when the rake is behind us and the shovel awaits us.

“I’ve got a birch here in my yard I’m looking at right now that looks like it’s the middle of summer,” he said while out raking Thursday on Green Bay’s east side. “It’s green. Hasn’t changed at all. They should have been long yellowed and off. They’re usually one of the first ones, but it’s hanging in there perfectly. I don’t know what’s going on.”

What’s going on is that many leaves are extremely slow to come off this year. You always get your perennial slowpokes, like Crimson King maples and oaks, which hang on to many of their leaves into winter. But even traditionally on-time species like silver maples and boxelders are behind schedule — as much as Mother Nature operates on a schedule, that is.

You can thank our changing climate for the stubborn foliage that’s causing this year’s late-season leaf crunch, said Laura Jull, horticulture professor and extension specialist for woody ornamentals at the University of Wisconsin-Madison.

Before you start shaking your rake at your trees in frustration, consider what they have been through in the last couple of months. There was that six-week very dry period starting in August. In September, when temperatures normally begin to decrease, it remained warm and dry. Drought-stressed plants shut down and didn’t deliver as much fall color in October, Jull said.

Then came really cold temperatures into November, with leaves still on the trees. The layer of tissue called the abscission layer that develops at the base of each leaf stalk, where it connects to a stem, didn’t get a chance to develop, Jull said. It’s that layer that allows the leaf to be shed.

“Plants are just growing later and later into fall ... and then they get blasted with cold weather,” said Jull, who has a magnolia with leaves that froze on and haven’t dropped yet. “They’ll eventually fall. It’s just late.”

Tricky timing

Things get tricky, however, for municipalities that collect leaves for residents. They do their work on a schedule, and it’s a rather tight one. The city of Green Bay is scheduled to wrap up its curbside leaf collection Nov. 17, although it may do some spot cleanup as weather allows.

Steve Grenier, the city’s director of public works, says his crews work off historical trends to best determine collection schedules. As much planning and revising and adapting to conditions they do, there’s only so much wiggle room when you get into the time of year when people are starting to thaw their Thanksgiving turkeys.

Even with this year’s late leaves, he has to turn his attention to what comes next.

“By mid-November, I need to start thinking about snow, regardless if those leaves are down or not," he said. "That’s just living in northeastern Wisconsin."

Many of the same vehicles the city uses for leaves are also used for plowing and anti-icing, he said, and it’s important they get in the shop in time to be converted for winter duty. About eight have already been transitioned and were used for brining streets in the last two weeks. 

A few pieces of leaf collection equipment — the city uses a mix of vacuum trucks, front-end loaders, baling tractors and customized rear-loading garbage trucks — will remain available for picking up “stragglers,” if the weather cooperates, Grenier said.

“There’s just piles and piles on neighborhood streets, and it’s Nov. 16,” said Hartman, a master gardener who also works part-time as a horticulture assistant with the Brown County UW Extension. “I just don’t remember (the street crews) working so hard and then looking up in the skyline and seeing there’s still a lot to fall at this time of year.”

For those late leaves, Grenier and Jull remind homeowners of the non-rake alternative: mulching them.

“Run a lawn mower over them and you have free fertilizer for your lawn and trees,” Jull said.