BY KATIE GOODE DONALDSON, WFA GRIZZLYCORPS FELLOW
Background
Meet the Farm
In California's San Joaquin Valley, Jessie’s Grove Winery has built a farming system where biodiversity isn’t just a value, it’s a practice.
When Joseph Spenker arrived in Lodi in the 1860s, he was searching for land "where the oak trees grew the tallest." He found it, planted his first vineyard in 1888, and many of those vines are still producing today. But it was his daughter Jessie who shaped what the farm would stand for. In the 1940s and 50s when the Central Valley was rapidly transforming, she set aside a 32-acre oak-covered parcel and refused to develop it. The grove and the winery were named in her honor.
Oak-covered parcel of land at Jessie’s Grove (left); Vineyard and waterway (right)| Photo credits: Katie Goode Donaldson
Eco-Region
The winery sits a few miles from the city of Lodi at the northern edge of California’s San Joaquin Valley where the Sacramento-San Joaquin Delta meets wine country. The region has long, hot, dry summers and mild winters.
Aerial photograph of San Joaquin Delta. formulanone, 2013. Wikimedia Commons, CC BY-SA 2.0.
The Challenge
Despite the region’s agricultural productivity and ecological potential, the Central Valley faces significant environmental challenges. Wetlands and riparian forests have been lost across much of the landscape. As habitat disappears, so do the natural checks on rodent populations, leaving vineyards more susceptible to gopher, vole, and mouse pressure. At the same time, rising input costs are putting increasing pressure on growers to fine-tune every management practice to be profitable.
"WHEN THE LAND DOES WELL FOR ITS OWNER,
AND THE OWNER DOES WELL BY THIER LAND - WHEN BOTH END UP BETTER
BY REASON OF THEIR PARTNERSHIP - THEN WE HAVE CONSERVATION"
-Aldo Leopold
Turning Point
The principles of conservation that Jessie Spenker followed didn't end with the oak grove. Today, Jessie’s Grove Winery is a certified member of LODI RULES America's original third-party certified sustainable winegrowing program, built on standards across six categories including ecosystem management, soil health, water management, and pest management). As part of that commitment, Jessie’s Grove has embraced an IPM conservation strategy: inviting natural predators back to the vineyard.
AN AVERAGE BARN OWL FAMILY CONSUMES
3,000–4,000 RODENTS A YEAR. PER FAMILY. PER BOX.
What They’re Doing
Jessie's Grove has installed 24 nest boxes across the vineyard, providing safe, year-round nesting habitat at a fraction of conventional rodent control costs. Barn Owl boxes are used as working infrastructure, a practical, chemical-free cornerstone of integrated pest management. Owls measurably reduce gopher, vole, and mouse activity in vineyards. As rodent generalists, they eat whatever prey is available, and Barn Owl populations can grow to meet demand. What limits them in farmland isn't food, it's shelter. Barn Owls are secondary cavity nesters: give them a home, and they'll do the rest.
Design of Jessie's Grove’s Barn Owl box (left); Owl documentation within boxes on the vineyard (right). Download WFA's Barn Owl Box Plans Here.
What It Costs
Barn Owl boxes are one of the most affordable pest control options available, and the numbers show why.
| Barn Owl box | Conventional trapping | |
| Setup cost | ~$750 | Minimal |
| Lifespan | 10+ years | Ongoing purchase |
| Cost per acre per year | ~$30 | $100 - $300+ |
| Cost per rodent killed | $0.11–$1.13 | $1.42–$5.82 |
| Annual upkeep | Simple cleaning | Repeated effort & labor |
| Licensed applicator needed | No | Sometimes |
Larson, Baldwin, and Johnson. 2026. Human Wildlife Interactions, In press. | Contact Matt Johnson for more information [email protected]
The Research
Researchers at Cal Poly Humboldt and UC Davis are tracking Barn Owls at Jessie’s Grove using GPS tags attached to the birds' backs, capturing one data point per second; a high level of resolution that reveals detailed hunting behavior across the landscape.
One week of nightly movement data for one Barn Owl
What the data shows is real diversity: some owls hunt primarily on the property, while others range across neighboring vineyards. You can't control where an owl hunts, but that's part of the point. Broader community engagement creates a Barn Owl box network , that extends rodent control across the landscape, benefiting not just one farm but many.
WHAT JESSIE'S GROVE BUILDS,
OTHER FARMERS IN THE VALLEY BENEFITS FROM
This is the reciprocal relationship that can exist between farms and wildlife sharing the same land. The owl gets a home. The vineyard gets a hunter. The land is richer from this partnership.
What It Means for the Region
In a landscape where vineyards stretch for miles, a single farm's choice to conserve an oak woodland, build owl habitat, and forgo rodenticides ripples outward. What works here, in one of California's most intensively farmed valleys, offers a model for every grower navigating the pressures of productivity and ecological health.
_______
Matthew Johnson, Professor of Wildlife Habitat Ecology, and Lauren M. Jackson, Graduate Student, both at Cal Poly Humboldt were consulted for this article.