The Grape Escape: How Flooding and Excessive Rainfall Affect Grapevines

The Grape Escape: How Flooding and Excessive Rainfall Affect Grapevines
sunstone estate and the santa ynez river
Jon Flores

Written by Jon Flores

Education and Experience Lead

In recent years, we have seen an increase in extreme weather events, and one of the most devastating of these is flooding. When a flood is said to be a “100-year flood”, it means that there is a 1% chance of that level of flooding occurring in any given year. This type of flooding can have a significant impact on communities and the environment, including vineyards and grapevines. The Sunstone Estate knows the effects of these 100 year floods all too well because part of our estate includes a 100-year flood zone. In this area of the estate we see the Santa Ynez River expand so much that it can at times flood our Syrah blocks, leaving them sitting in water for a few days. Consequently these vines have developed a strong and deep root structure and, based on past experience, may not need much or any irrigation during the 2023 growing season. But what negative effects can come from this year’s heavy rains?

Excessive rainfall can affect soil health by causing erosion and nutrient loss. Soil erosion occurs when the topsoil is carried away by the rainwater, which can lead to a loss of organic matter, nutrients, and the microbial life that is essential for healthy soil. The loss of soil nutrients can affect the growth and development of grapevines in the following growing season. Additionally, heavy rainfall can compact the soil, making it difficult for roots to penetrate and absorb water and nutrients. The most effective and beneficial way to prevent these issues is to incorporate a healthy and dense cover crop in the vineyard. The roots help keep the topsoil I place and use some of that rainfall to grow. Later in the season when the rains have stopped we will come in and mow the cover crop and till it into the soil to be absorbed by the grapevines as it decomposes. This cycle of nutrients is crucial in organic farming.

sunstone vineyard cover crop

During the dormant season, grapevines are in a state of rest, and excessive rain can affect the grapevines differently than if they were actively growing. The waterlogged soil can suffocate the roots, leading to root damage, rot, and the inability to absorb necessary nutrients. As a result, this can impact the vine’s growth and development during the subsequent growing season, potentially leading to lower yields and poor fruit quality. In contrast, excessive rain during the growing season can lead to rapid vine growth and an increase in canopy density, which can cause shading of the grape clusters and promote the growth of fungal diseases. We will mitigate these issues with diligent canopy management to ensure the best quality environment for the vines to grow.

Despite the potential negative effects of excessive rain on vineyards, it is important to note that there is still a positive outlook for the 2023 growing season. Furthermore, vineyards that have experienced flooding can also benefit from the nutrients and organic matter that the floodwaters deposit on the soil. This can help replenish the soil, promoting healthy vine growth and fruit quality.

In conclusion, excessive rain, especially during the dormant season, can have a detrimental effect on soil health and grapevine growth. However, with the right precautions and management practices, vineyards can still produce high-quality grapes, even after extreme weather events. So let’s look forward to the 2023 growing season with optimism and continue to take care of our vineyards to ensure that they thrive for years to come.