Michigan Terroir: How the Great Lakes Make Great Terroir

Nestled in the northern latitudes between the 41st and 49th parallels, Michigan faces both challenges and advantages growing grapes. The Great Lakes play a starring role.

Harsh winters, with temperatures diving below 0°F (-20°C), threaten to kill grapevines. Yet, it's under these exacting conditions that Michigan crafts its most elegant wines.

The region's cooler climate yields wines with refreshingly lower alcohol, vibrant flavors, and age-worthy traits.

The three biggest contributors to Michigan’s unique terroir define its wines:

  • The Mitten's gentle geography helps protect grapevines
  • The "lake effect" makes it possible to grow grapevines in Michigan
  • Glacial soils define Michigan wine's distinct aromatics

Let’s dive into each point a little deeper.

The gently rolling hills and sandy loam soils are both due to glacier retreat more than 10,000 years ago. Photo by Aaron Burden.

The Mitten's Gentle Geography Protects Grapevines

The shape of Michigan is iconic, with two distinct peninsulas: the Upper and the Lower. The Lower Peninsula, affectionately known as the Mitten, is the heartland of grape growing. Here, the landscape is gentler, with rolling hills and free-draining soils, all benefiting from the lake effect more profoundly than the wild, rocky, and forested Upper Peninsula.

Glacial Scars

This distinctive landscape was shaped over 10,000 years ago by the last ice age when glaciers retreated northwards. It created the Great Lakes. These natural borders and water resources are pivotal to Michigan's terroir, making viticulture viable by softening the winter's bite and extending the growing season.

Indeed, no point in the state is more than six miles (9.7 km) from a natural water source!

This unique geography sets Michigan up to be one of the agricultural states and, in fact, is second only in diversity of agricultural products to California.

Lake Michigan is the 5th largest lake on the planet, and is the main contributor to the Lake Effect for vineyards in the state. Photo by: Good Harbour Vineyards

The "Lake Effect" Makes It Possible to Grow Wine Grapes in Michigan

Michigan's vineyards sit between the 42nd to 46th parallels in a northern latitude where grape growing is challenging. The presence of the Great Lakes provides a moderating influence essential for viticulture, allowing Michigan to produce diverse wines despite its northern location.

The "Lake Effect"

The phenomenon known as the "lake effect" extends the growing season into the fall and shields the vines from the harshest winter freezes. Lake Michigan acts like an inland ocean due to its vast size. It absorbs heat throughout the summer and releases it slowly in the fall, warming the surrounding landscape as the cooler months approach.

We see a series of microclimates around the lake shores where temperatures remain more stable, allowing a wider variety of grapes to ripen fully.

For example, Riesling can hang on the vine longer, developing a spectrum of flavors for a variety of styles from bone dry to lusciously sweet. It's also possible to ripen Pinot Noir and Cabernet Franc.

Frozen grapes being harvested in late fall for Ice Wine. Photo by: Chateau Chantal.

Michigan's Cool and Continental Climate

Michigan has a cool, continental climate marked by cold winters and warm, somewhat humid summers. The relatively short growing season means selecting grape varieties that mature early with resilience to spring frost is key.

Snow and Rain

Precipitation plays its part too with the region receiving around 27.5 inches (700 mm) of rain annually, which is enough to sustain vine health without causing waterlogging thanks to the well-drained soils.

Winter brings snow, and a lot of it! Often reaching over 10 feet (3 meters) courtesy of the lake effect, this snow cover acts like a winter jacket for the vines, insulating them against the cold. This wintery weather also allows for grapes to freeze on the vine, producing Ice Wine when conditions are just right.

Sandy and sandy loam soils are prevalent in vine growing areas and provide great drainage and increased aromatics for grapes. They are leftovers of glacial retreat. Photo by: Blue Dot Farm.

Glacial Soils Define Michigan Wine's Distinct Aromatics

What soils you find in the vineyard truly depends on location and underlying bedrock, which can include limestone, granite, or clay. Wines grown on limestone soils or bedrock tend to have higher levels of acidity, adding brightness and age-worthy structure to wines.

Meanwhile, sandy soils not only help prevent ground freezing but also impart an aromatic lift to the wines. Expect intense fruit aromas, particularly in varieties like Riesling, where the sandy soil composition enhances the wine's expressive character.

Gravelly soils tend to bring structure (e.g. more tannin) to wines which is particularly important for Michigan's red wines but can also contribute to ageability in white wines too.

A Glacial Legacy in Michigan's Soils

The legacy of glaciers manifests in a mosaic of soils, predominantly sandy loam and glacial deposits. These soils, shaped by ancient moraines, offer a diverse range, from gravel to sandy loam and gravel loam. Pretty much all of the soils are free draining here which helps reduce leafy vigor in the vines (aka: great for wine quality!).

This diversity ensures good drainage, essential for vine health, while the sandy soil warms quickly in spring, vital for the region's short growing season.