SAN FRANCISCO - Napa Valley, one of the world's premier wine-growing regions, has an uncommon problem these days: not enough new grapevine rootstock is available to supply the massive replanting that's under way there.
A trifecta of developments has created the critical shortage:
• Aging cabernet vines planted after a deadly phylloxera outbreak in the 1980s are due for replacement that was deferred for years as sales of premium wines slumped in the recession.
• With demand again strong, growers are taking the opportunity to replace old vines with varieties and clones better suited for their microclimates.
• Others are reconfiguring rows to prevent erosion into sensitive streams, or to allow mechanical harvesting machinery to access vines.
All of this activity caught commercial nurseries across California short of supply. Some are sold out for 2013 and are taking orders for 2014 and beyond.
"I've never seen anything like this," said Michael Monette of Sunridge Nurseries, one of the industry's biggest suppliers of plants. "What's totally phenomenal for me is, I'm focusing on 2014 and 2015, which is absolutely nutso. We have no more space in our greenhouses."
Napa Valley, an hour's drive northeast of San Francisco, caught the world's attention in 1976 when, to the shock and chagrin of the French, wines from Stag's Leap and Chateau Montelena won the Paris Wine Tasting.
Nearly two-thirds of the vines there slowly died, and vineyard owners yanked millions of plants beginning around 1990 then spent $1.2 billion replacing them.
That replanting of new clones on more resistant rootstock are the vines on which the Napa Valley's current reputation for excellence was sealed. Today wines from Napa Valley's 16 sub-appellations are some of the most complex and priciest produced.
After 20 years, however, plants reach old age and yields begin to diminish in a region where a ton of grapes can fetch $4,500 or more.
Growers routinely replace plants, but the convergence of events has created an urgency that prompted the Napa Valley Grapegrowers to gather experts last week to talk about planning, plant financing and even preventing erosion in a region of sensitive habitat.