The secret's in the soil
What is the best fertilizer to use on grapevines, and when should I apply it?
— Raymond, Bogota, NJ
Roger Cook replies: Grapes are deeply rooted plants that usually don't need a lot of fertilizing. If the soil is naturally rich, you may only have to fertilize once every two or three years. For well-established vines, I'd scatter 1/2 to 1 pound of 10-10-10 fertilizer around the root zone, ideally in the early spring. But the actual amount and type of fertilizer you use depends entirely on your soil conditions. So your first order of business should be to have the soil tested by your local cooperative extension service.