Every year, towards the end of winter, many Sonoma County vineyards come alive with a brilliant carpet of mustard showing yellow, orange, and gold beneath the bare grape trunks. The first time someone sees the landscape, it’s mesmerizing. Even when they see it again and again, year after year, it never loses its magic.
Whether it’s growing wild or planted by thoughtful vineyard managers, mustard is more than just a feast for the eyes, it’s a feast for the vines. It thrives just until bud break, when it is turned under to mulch and provide valuable nutrients and phosphorus to the emerging grape plants.
The practice holds deep roots in Wine Country. According to legend, a Franciscan missionary first spread the mustard seed while landscaping church properties throughout California. Planting was simple – these early world gardeners carried the mustard seeds in a sack slung over their backs, and each sack had a small hole in it, so as they walked, the seeds would scatter.
Mustard also thrives wild in meadows, laying a luxurious blanket under live oaks. It’s beneficial on sloped grades, since the plants hold soil in place during winter rains to protect again erosion. Sometimes, it seems to just pop up overnight, too, in a place that long was barren. That’s because mustard seeds have been known to persist in soils for upwards of 20 years, and may have gone dormant but will be revived by specific weather conditions or tractor disking.
For folks wanting to impress their friends with mustard knowledge, here are some details about the plants that will have everyone marveling over the science (and big words) of it all:
Mustard growth helps suppress nematode population (microscopic worms that can damage vines), because mustard contains high levels of biofumigants
Some vineyards have created their own varieties that are specifically bred to have high levels of Glucosinolate compounds, or are “extra spicy,” to further deter nematodes
Essentially, the worms don’t like the glucosinolates in the mustard, which give the plant its pungent odor and sharp taste
Naturally reducing harmful nematodes with mustard spares the vineyards from dangerous chemical eradicators and pesticides