For Earth Day, we thought we would share an update from our Vineyard Liaison Laurence Donald. Laurence spends countless days inspecting and sampling the over 20 Pinot Noir Vineyards and numerous Chardonnay vineyards throughout the Russian River Valley and county of Sonoma. With an early bud break, there is the off-chance that we may encounter a frost issue that would upset the delicate growth of the new shoots throughout most of our vineyards. Take a moment and learn about the climate in Sonoma County this Earth Day, and what our vineyard partners do to alleviate the potential threat of frost.
Mid-way through February the SF Chronicle was writing about how the drought area had tripled in 3 months, now affecting 92 percent of California. They reported that the dry winter has left the mountain snowpack at just 20 percent of its average level. Then we got the last two rounds of storms that dropped many feet of snow in the mountains and certainly brought us back to a more reasonable rainfall average in Sonoma county at 76% of normal.
Not to harp on a theme, but still the biggest concern for farmers is frost risk. The warmer weather during the recent storms lowered the risk dramatically, but in February frost measures were in effect. We won’t be out of the woods entirely until mid-May which is the latest date of any known frost event.
The three common methods of frost protection are:
1. Late Pruning: Pruning as late as you can naturally delays a vine’s bud
2. Stir the air: Once vines are pruned; fans and hot pots are used to try to circulate the air. Cold air sinks, so if you can keep the air in a vineyard moving, the warmer air above the vines will mix in with the coldest air sitting on the vineyard floor. Even one degree above freezing helps.
3. Sprinklers: If that layer of cold air is just too deep and running the fans doesn’t bring enough warm air into the fruit zone, turning on the sprinklers can be a next line of defense. By creating a thin layer of ice and, critically, by keeping that layer of ice wet, the temperature of the bud won’t get below 32 F.However, if you let the ice dry out and it starts to evaporate, you can actually exacerbate the freeze by the evaporative cooling effect of the water. Similarly, if temperatures get below 23-24 F, this ice shield simply doesn’t offer enough protection. For this reason sprinklers can only be used under very specific conditions. Luckily, any water used this way will sink bank into the soil and eventually replenish the vineyard water table.
LEFT: Carneros, February
Bud break started early with some new buds greening up as early as the first week of March, but was stalled completely by colder weather that lasted for several weeks. Most blocks finally started to sprout by the last week of March.
RIGHT: McDonald Mountain, late March
The growth has been very even and with all the rainfall it is very vigorous. Fingers crossed we don’t get any major cold spell. Spring is definitely in the air…time to start thinking about our gardens.