Recommendations from Jeff Wheeler for your vineyard after a wildfire
Burned areas should be reseeded before the heavy rains come, especially in areas with any slope. I recommend an erosion control blend of seeds, which will generally include annual grasses. Even on flat areas in vineyards it’s a good idea to re-seed as this will help tractor practices in spring.
Determine if your vines are dead or alive. After a fire, burned vines may still be alive depending on how hot they got. Fire can damage the vascular structure of a plant—in some cases the fluid that runs through the xylem and phloem will actually boil. When this damage is widespread throughout the plant the vine will generally not survive.
A couple of weeks after a fire one can cut though the bark of the vine and observe the color of the vine interior to assess the condition. If the color is any shade of brown or black, this generally means the vine is dead. If the color is light yellow or green then the vine has survived the burn. Many times the cordons or distill spurs will be killed while the thicker upper trunk sections will survive. In these cases, cutting back the vines to the central trunk will be necessary.
Ash in itself is not an issue for the soil or the vines but it can be so heavy as to coat leaves, which may cause reduced photosynthesis. The best way to remove ash from vines is to apply overhead water if possible. Wood ash will not be harmful to soil and can actually be a benefit as it contains potassium, magnesium, phosphorus and other minerals.