I have a potted Grapevine that I planted in May. I keep it on my balcony where my apartment gets the most sun. After a few weeks it grew lovely canes and leaves. But now (late August) all the leaves have dropped off and the canes are going brown. I have never fertilized the plant and I have not been watering it very much, as I thought it diddn't need it at first. I don't want it to die. Is there any way to save it?