morton_fullxfull.259666386

Waterloggerheads

When it rains, as they say, it pours. And it couldn’t be more true for Napa Valley this week. According to Accuweather, St. Helena got over five inches of rain between March 14 and March 21st. Well, be careful what you ask for, because while some rain was sorely needed, we have seen some flooding on the valley floor.

Matt Iaconis of MSix wine group says that some Oakville properties were waterlogged and forced to pump. “Others just let it sit and hope their cover crop and the warm weather dry things out before the lack of oxygen affects the roots and before severe nutrient depletion.”

According to a study by the Department of Primary Industries in Victoria, Australia (which suffered much during cyclones last year), “Grapevines will tolerate 3 to 7 days of soil waterlogging before showing signs of reduced growth. Longer periods of intermittent waterlogging (3 days waterlogging every 14 days for 18 weeks) reduced total growth of the vines by 36 percent.”

But if there were a time to be waterlogged this would be it. “These problems are more relevant during periods of active root growth, between flowering and version and after harvest,” says the report. In other words, not right now.

Hillside vineyards with their rocky slopes have a tendency to fare better during these outbursts from Mother Nature. Harlan Estate held off on mowing their cover crop in anticipation of the rain and it has paid off — we saw no signs of waterlogging or swampiness when we visited this week. Vineyard Manager Mary Maher is feeling pretty good about the season overall: “Even though rainfall is lighter this season it has been great that we are going into bud break with our soils saturated. If we got a few more inches it would be nice but it won’t hurt us if we don’t. Regarding early season vine growth, I’d rather have less rain than too much during the growing season.” Maher also says that many vintners are experiencing peace of mind  now that their reservoirs are full so that they can irrigate later in the summer.

Some of the most notable vineyards in Oakville, such as To-Kalon, consist largely of clay loam, with excellent drainage, so are blissfully free from much of the waterlogging and muddiness now plaguing other Valley vineyards after a solid week and a half of steady rains. “There are perched water tables in our area [of Oakville] which are sub layers of clay or abrupt soil changes that take longer for the water to permeate through,” explains Graeme MacDonald of MacDonald Vineyards (who manages To-Kalon and other Horton vineyards). “However those tend to dry out quickly and are not of concern except for compaction from equipment.”

MacDonald further elucidates, “The water logging you are seeing along the rivers is different, but the vines are still dormant so they should be fine. If they were actively growing, the waterlogging would deprive the soil and living organisms of oxygen, stunting vine growth.” The wet and muddy conditions on much of the valley floor will also delay the ability to do tractor work, because the machines can seriously compact the soils if started when conditions are too wet.

“Most farmers will be itching to mow soon because mowing will allow cold air to flow out of the vineyard better and lower the frost zone relative to the vine,” MacDonald says. Then he added, “Did you hear the wind machines last night?”

Everyone loves a good wind machine.

In Sonoma, conditions are much drier. Please look forward to a complete (considerably less soggy) report on Sonoma next week.