Vineyard Due Diligence Checklist: Napa & Sonoma

Vineyard due diligence answers four questions before you’re committed: is the water there, legally and physically; are the vines healthy and how long will they last; do the permits match what’s on the ground; and is the income real. The checklist below is the one we work through with buyers in Napa and Sonoma. Use it to request records on day one of escrow and to brief each specialist.

What should you ask the seller for first?

Ask for the vineyard’s paperwork before anyone walks the rows. Gaps in the records are findings in their own right.

• A block map with each block’s variety, clone, rootstock, row and vine spacing, trellis type and planting year
• Yields by block for at least five vintages, and the price received per ton
• All grape purchase agreements, amendments and notices, plus any winery that declined fruit
• Farming records: pesticide and fertilizer use, irrigation schedules, frost events and the pest-control operator’s permits
• Well logs, pump tests, water-quality results and any water rights filings for ponds or reservoirs
• County permits: erosion control plans or VESCO permits for each planting, building permits and finals for every structure, and any winery use permit with its conditions
• Any Williamson Act contract, conservation easement, notice of violation or open code case
• Insurance history, including crop insurance claims and any fire or smoke losses

Water: is there enough, and is it legal?

Water decides a vineyard’s value more than almost anything else. Confirm both the physical supply and the right to use it.

Vines: how healthy are they, and how long will they last?

Have a viticulturist walk every block, ideally during the growing season. Leaves, fruit and canopy show problems that a winter visit hides.

• Virus testing. Leafroll disease, spread by mealybugs, can move through a vineyard even at low insect numbers, and an infected vine may not show symptoms until the next season, according to UC IPM. Commercial labs test for viruses by ELISA and PCR. Agree on the sampling plan with the lab first, because timing affects false negatives.
• Red blotch. The virus behind red blotch disease was identified in 2012. California’s grapevine certification program, run with Foundation Plant Services at UC Davis, added it to the diseases it screens for (CDFA). Ask whether blocks were planted with certified stock and whether any tested positive.
• Vine age and vigor. Older blocks can make prized fruit but bring a replanting decision within the holding period. Count missing and weak vines per block.
• Pests and diseases common to the area, such as mealybugs, Pierce’s disease near riparian zones and powdery mildew pressure.
• Trellis, irrigation and frost equipment. Posts, wires, drip lines, filters, pumps and wind machines all have service lives and replacement costs.

If replanting looks likely, cost it with our vineyard development and replanting guide, including the three or four seasons without a commercial crop.

Soil, slope and site

• Pull the NRCS Web Soil Survey for the parcel, then confirm with backhoe pits or soil samples where it matters.
• Map slopes. In Napa County, earthmoving on slopes over 5% needs an agricultural erosion control plan, and 30% to 50% slopes need a use permit exception (Napa County). Expansion plans should be checked against those lines.
• Check stream, wetland and oak woodland areas, which carry setbacks and canopy rules in Napa and habitat reviews in Sonoma.
• Look at frost pockets, cold-air drainage and wind exposure with the vineyard manager.

Permits, zoning and land-use limits

Match every vine and every building to a permit. The question isn’t only what the property is allowed to do today, but what you plan to do with it.

• Plantings: each block should trace to an approved Napa erosion control plan or a Sonoma County VESCO permit or registration. Sonoma requires a VESCO permit before planting or replanting begins (Sonoma County).
• Buildings: houses, second units, barns, farmworker housing and wells need building permits and final inspections. Unpermitted structures are common on older ranches and affect insurance and financing.
• Winery use: read the use permit itself for production limits, visitor numbers, events and conditions. In Napa, the 1990 Winery Definition Ordinance requires at least 75% Napa County fruit for new or expanded wineries.
• Williamson Act: a contract binds the buyer and limits non-agricultural uses; early cancellation costs 12.5% of current market value (Department of Conservation).
• Right to farm: Sonoma County uses a right-to-farm disclosure. It tells neighbors that normal farm operations are protected, which matters if you plan a residence next to someone else’s spraying and harvest lights.

Title, access and boundaries

• Review the preliminary title report for easements, access rights, mineral reservations and recorded agreements with neighbors.
• Confirm legal and physical access, especially on shared private roads, and who maintains them.
• Order a survey where fences, roads or vine rows may cross a boundary.
• Check whether pipelines, wells or ponds serve neighbors under recorded or informal agreements.

Income: is it real, and will it survive the sale?

Read every grape contract in full. Note the term, price formula, tonnage commitments, quality standards, and what happens on a sale of the property. Then call the buyer, with the seller’s permission, to confirm the relationship.

In the current market this step matters more than it used to. Turrentine Brokerage reported Sonoma Chardonnay’s 2025 district average at about $2,370 a ton while spot sales ran closer to $800. A contract that ends at closing can cut a vineyard’s income by more than half. Our guide to vineyard valuation shows how contracts feed into the price, and vineyard leases covers vineyards that are leased to a grower.

Fire, insurance and environmental checks

• Check the CAL FIRE fire hazard severity zone and the property’s fire history, including any smoke-exposure fruit rejections in 2017 or 2020.
• Get insurance quotes for the house, buildings and equipment early. Coverage availability can change a deal.
• Review pesticide-use records and storage areas. For a winery, consider a Phase I environmental assessment covering fuel tanks, wastewater and chemical storage.

Labor and operations

• Find out who farms the vineyard and under what agreement. Farm labor contractors in California must be licensed by the Labor Commissioner (California DIR). Ask for the contractor’s license number and check it.
• List employees, housing provided and any obligations a new owner would take on.
• Collect the equipment list and service records.

For choosing who farms it after closing, see vineyard management in Napa and Sonoma.

Buyer-specific checks

• Foreign persons who buy an interest in U.S. agricultural land must file USDA form FSA-153 within 90 days, with penalties up to 25% of market value for late or missing reports (USDA FSA).
• Lenders may order their own agricultural appraisal and environmental review, which adds time.

Who does what

Questions buyers ask

How long does vineyard due diligence take?

Thirty to sixty days is common, set by how quickly the specialists can be scheduled. Ask for longer if you need a growing-season vine inspection or a late-season pump test.

Can I test vines for viruses before buying?

Yes. Labs test leaf or cane samples by ELISA or PCR. Sampling timing affects accuracy, so plan it with the lab, and test the blocks that carry the most value or the most doubt.

What if a building isn’t permitted?

Find out what it would take to permit it, or whether it must be removed, and price that in. Unpermitted structures can also limit insurance and loan options.

Is a pond on the property a water right?

Not by itself. A pond that stores water diverted from a stream generally needs a state water right or registration. Check the Water Board’s records and the seller’s filings.

Want help organizing this for a specific property? Talk to us about a vineyard you’re considering. For the whole purchase sequence, read buying a vineyard in Napa or Sonoma, or return to vineyards and wineries for sale.

Sources & notes

• UC IPM: grape virus diseases; CDFA: grapevine certification and red blotch testing
• California Natural Resources Agency: groundwater sustainability plans; Russian River frost regulation
• NRCS Web Soil Survey; Napa County conservation regulations; Sonoma County VESCO
• Williamson Act FAQ; Permit Sonoma right-to-farm disclosure
• Turrentine Brokerage via Wine Industry Advisor; California DIR: farm labor contractor licensing; USDA FSA: AFIDA

This checklist is general guidance, not legal, agronomic or engineering advice. Each property needs its own specialists. Last reviewed October 2026 by Matthew Martinez.