What the FOG?! Why Are Growers Digging Holes in the Middle of Winter?

Dr. Paul Anamosa

​If you spot vineyard crews digging holes, don’t worry, no one lost anything important. This is soil sampling season, and it’s one of the smartest ways growers prepare for the year ahead.

While grapevines are enjoying their winter dormancy, growers are busy learning what’s happening below the surface. Because when it comes to great wine, it all starts with the soil.

So… What Are They Looking For Down There?

By digging soil pits and taking samples, growers can study:

• Nutrient levels (like nitrogen, potassium, and phosphorus)
• Soil texture (sand, silt, clay—or a mix)
• Drainage and compaction
• Organic matter

Think of it as a vineyard health check-up. The soil tells growers what the vines already have—and what they might need more (or less) of once growth begins.

From Dirt to Decisions

Soil data doesn’t just sit on a clipboard. Growers use it to:

• Customize nutrient programs block by block
• Avoid over-fertilizing (which vines definitely don’t need)
• Improve soil health sustainably over time

In a place as diverse as Napa Valley, two vineyard blocks right next to each other can have completely different soils. Digging holes helps growers treat each section exactly how it needs to be treated.

It may look like winter busywork, but those muddy boots and soil samples are laying the groundwork for the entire growing season—and ultimately, the wines we’ll enjoy down the road.​​

Dig Deep into the Coombsville AVA on the Podcast with Soil Scientist Dr. Paul Anamosa and Dr. Nick Madden