Remove all damaged and dead wood in late winter/early spring. Place the dead and damaged wood in a bag.
Fertilize your Thompson Grape Vines once in the early spring before new growth begins. Spread a 10-10-10 ratio fertilizer around the vine, 6 to 8 inches from the base of the plant.
Water grapevines after fertilization so the fertilizer can penetrate the soil and reach the roots of the vines.
Fertilize again in the fall with a nitrogen-based fertilizer after harvest.
Break the soil up around your Thompson vines to keep the ground from freezing.
Water the area around vines thoroughly to make sure the fertilizer can reach the roots.