In general you do not need to fertilize the soil when making hardwood cuttings. The plant is busy making roots and not requiring added nutrition. Once you see new growth or sprouts from the buds of the grape vine cuttings, then add fertilizer. I would suggest one teaspoon of Osmocote for a one gallon container as the label suggests. You can use the Osmocote made for flowers and vegetables or the Osmocote made for containers called Osmocote Potshots. The Osmocote releases nutrients based on soil temperature and moisture . This means during the growing season when the soil is warm the fertilizer is slowly released. After about six months the fertilizer capsules are empty and winter returns so the plants go dormant and do not require plant food. This means you should reapply the Osmocote to your containers every spring. You can also use a diluted (half strength) liquid plant food such as Miracle-Gro on potted plants in spring if the weather is cold but the plants in the pots are showing robust and active growth. The Osmocote will stay inside the round pellets during cold weather but liquid plant foods provide nutrients almost immediately. Good luck with your cuttings and Keep Growing, Marianne Binetti