Wine Arcana

Concept

Spring frost

Spring frost can damage grapevine buds and young shoots just as the growing season begins. It can remove much of a year's potential crop even when the permanent vine survives. Susceptibility increases as buds open and tender growth develops, so the timing of a cold event relative to budbreak is crucial.

Why one vineyard freezes before another

During a radiation frost, clear skies allow surfaces to lose heat at night, often with little wind. Cold air collects in low places, and warmer air may remain above it: a temperature inversion. Slopes that allow cold air to drain can consequently fare better than nearby hollows.

An advective freeze is different. A moving cold air mass brings freezing conditions over a wider area, often with wind. The distinction matters because a protection method relying on warmer air above the vineyard has little to work with when that warmer layer is absent.

Budbreak and protection

Varieties differ in when they start growth. Early budbreak increases the period during which green tissue may encounter spring cold. This is a separate trait from winter hardiness: a variety can survive a severe dormant-season freeze and still lose its new shoots in spring.

Growers can sometimes delay budbreak through pruning choices. Oregon State University describes retaining extra cane length or spare canes until frost risk has passed. The method and its timing must fit the vine's training system.

Wind machines mix warmer air aloft with colder air near the vines during suitable inversion conditions. Overhead irrigation uses the heat released as water freezes, but requires a reliable, continuous water supply and suitable conditions. These mechanisms explain why equipment must match the site and weather event.

After injury, surviving secondary buds may produce replacement shoots and a partial crop. The resulting yield depends on the variety and extent of damage; visible regrowth does not necessarily replace all the lost fruit.

Sources