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After a warm winter, maple sugaring comes early in Wisconsin’s Northwoods

blue plastic tubes run through a grove of trees. there is snow on the ground
Courtesy of Martin & Sons Maple Syrup
The Martins began tapping in January, much earlier than the traditional sugaring season start.

Warming winters have shifted the timing and length of maple sugaring season in Wisconsin, the fourth-biggest maple syrup-making state in the nation. This year’s mild winter — on track to be Wisconsin’s warmest winter ever — is no exception.

Maple runs require a specific range of temperatures (days around 40 degrees Fahrenheit and nights below freezing), so they’re vulnerable to shifts in winter weather. The one-two punch of the Pacific climate pattern El Niño and climate change had Northwoods maple syrup producers scrambling to start tapping in January, long ahead of the traditional season start.

Climate change poses a slew of obstacles to the enduring practice of maple sugaring, from fickle winters and invasive pests to drought, extreme rainfall and declining sugar content in sap. Producers can adapt to these threats by preparing to tap trees earlier or boosting biodiversity that will protect their trees from pests and drought.

Karl Martin is the co-owner of Martin & Sons Maple Syrup, which he operates with his wife and three sons in Rhinelander, Wisconsin. Trained as a forest ecologist, Martin also serves as the dean and director of the UW-Madison Division of Extension. I spoke to Martin in late February, a few weeks after they began tapping.

This conversation has been edited for length and clarity.

a man and young man dressed in warm winter gear smile inside a wooden shack. the room is filled with steam
Courtesy of Martin & Sons Maple Syrup
Martin says the smell of fresh steam coming off a maple syrup evaporator is his favorite part of cooking maple syrup.

I spoke to your wife, Karen, and she said that tapping is underway. And that it's been a bit of a roller coaster. So, let’s start there. How's your week been?

Pretty good. We did get tapped a few weeks ago. Normally, we would still be tapping at this time of the year. But with this weather, we were pushed to tap very early, in January. Even with tapping that early, we probably missed a couple of runs. In my 50 years of making maple syrup, we have never seen sap flow in January, in the northern parts of the state. Usually you would have a lot of snow on the ground, deep frost or both. And this year, we have neither.

That is crazy. You would normally start around when …?

We would start tapping in February. But the sap normally would not run until early March this far north in the state. That's different in southern Wisconsin. It'll start in February in southern Wisconsin some years. But in northern Wisconsin, it's significantly cooler. And normally, we do not cook maple syrup until the middle of March.

What does that look like for you guys this year?

four jars of maple syrup of different shades of gold sit in a window
Courtesy of Martin & Sons Maple Syrup
Jars of maple syrup await tasting.

We cooked a batch a couple of weeks ago, we will be cooking another batch this weekend. It looks like we'll be cooking next Monday, Tuesday, which is still the end of February. We'll be cooking in early March as well.

The unknown is how long the season will last. That will really depend on temperatures. If we start to see 60s, 70s, the trees will bud out and the sap turns sour. The maple syrup doesn't taste any good. Once the trees bud out, the season is over.

What has it felt like to be monitoring the weather conditions and realizing that you're going to have to make some of these calls earlier than you have in years past?

It was a bit of a — and I think this is true for all producers — it was a bit of a panic in January, when you start to see the forecast with these warm temperatures. We run vacuum lines at our operation. With vacuum lines, you can tap them early, and you will continue to get sap for a couple of months.

The challenge is really for my friends and counterparts in the business, particularly small producers that use pails or bags. You only have a certain period of time in those systems before the tree is going to heal over and you're not going to have sap production. So in those cases, in January, a lot of them had to make a decision. Do we tap now understanding that we only have about 45 days? Or do we wait for more of the traditional season and tap in March? You had to assess the risk.

For those who are running a lot of taps, a lot of trees, part of the challenge was getting them all tapped. Because it takes a lot of time. We run about 4,500 trees. I have three sons and my wife, and it’ll take us and our friends several weekends to get those taps. For larger producers that are running 20,000-30,000 taps, it takes multiple weeks for their crews to get out and tap all those trees.

That's why I say the first runs were missed in January. Nobody anticipated that there would be good runs of maple syrup in the northern part of the state in January or early February, for that matter.

a red-roofed shack is surrounded by bare trees in winter. Steam comes out a vent at the top.
Courtesy of Martin & Sons Maple Syrup
Fresh steam billows out of the sugar shack, located in Rhinelander, Wisconsin.

And the potential impact of missing those runs, but then having the season get truncated — it can really hurt down the line? 

We probably missed 20% of the season by not being ready.

Could you talk about what it means to you to work with the land — and what it feels like when the course of things feels so off? 

We have a pretty close connection to the land. I've been cooking syrup for over 50 years. I grew up cooking maple syrup. It’s very unusual to have April-type weather in January and February.

When I'm out tapping trees, I start to think [about] what this is doing to the trees, to the insect populations. There's a lot of things that are coordinated, or evolved, with cold temperatures and deep snow. If you start taking that away from the system, there's a lot of natural processes that are not going to occur as they have in past years.

My concern for the land, the ecosystems, the trees is what does this do long-term? Particularly if you see this [winter] in multiple years. We're definitely seeing different winters than we had when I was growing up. We were never tapping trees in February, and definitely not in January. So what does that do to our systems moving forward? I think that's yet to be determined.

Do you get stressed out?

No, I don't get stressed out. I'm concerned. I do like to communicate with others who are either in the maple syrup business or other agricultural areas, just to understand what their experiences have been. You want to make sure that you're not personally over-exaggerating what's going on. When I talk to others, they have the same concerns.

Whether you believe in climate change or not, the weather this year is unprecedented. Everybody acknowledges that. There's just a lot of questions about what that means for the foods we produce, the ecosystems that we all enjoy. Particularly if we start to see this on a more regular basis, which it sounds like we may.

As a producer, I need to figure out how do I adapt. Next year, one thing that I would do is I would be ready to tap much earlier in the season. Fortunately, weather forecasts are getting better and better.

a man in a red hat uses an electric drill at the base of a tree. the ground is covered with snow
Courtesy of Martin & Sons Maple Syrup
Martin says when he's tapping trees, he thinks about how warming winters are affecting the ecosystem.

Being ready — what does that mean? Having equipment ready, having lines sanitized?

Yep, all of that. Making sure things are clean, making sure you have the available workforce to tap the trees and you're ready to mobilize. This year, we were caught off-guard. Like, “it's not going to run in January, early February, that would never happen.”

I think we learn lessons as we go through the seasons and we try to adapt next year. Now, it’s like, “that occurred in 2024. And that could occur again in 2026 or 2028.” You want to make sure you have a long enough memory. We need to adapt to these changing climate conditions that are impacting the state and the industry.

Absolutely. What’s your favorite part of the process? 

This is one of the reasons I cook maple syrup. My fondest childhood memory is the steam coming off of the evaporator. It has a very sweet and a very unique smell to it. There's nothing that mimics that smell of fresh steam coming off a maple syrup evaporator in the springtime.


Lina is a WUWM news reporter.
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