In general, grape vines are not heavy feeders and do not need much fertilizer after they are well-established. Too much fertilizer can stimulate wood and leaf growth rather than fruit production. Moderate amounts of fertilizer during the first and second years after planting will help stimulate young plants to size up for earlier fruit production.
I always go the organic route when feeding any plants that will end up on the dinner table. Organic vineyards choose organic methods to obtain the strongest and richest grapes possible, with the fewest detrimental effects on the environment, and their grapes reflect that dedication to quality.
Evaluate Soil
Before you feed your grapevines it's always a good idea to evaluate soil conditions.
Soil Preferences
Grapevines aren't too pick about soil type, tolerating a wide range of soils. That being said, they prefer a well-drained, fertile soil that is rich in organic matter. They don't like constantly boggy or wet soils. When planting in heavy clay or poor, infertile soils, it is highly beneficial to mix in some organic matter in the form of aged compost or composted manures.
Soil pH is Important!
Grapevines grow best in an an acid to slightly acid soil ranging from 5.5 to 6.5 on the pH scale. If you're unsure about the pH of your soil, it's a good idea to test it.
Testing Soil pH
Soil pH is a measurement of the alkalinity or acidity of soil and is measured on a scale of 1-14, with 7 as the neutral mark. Any measurement below 7 indicates acid soil conditions, and anything above 7 indicates alkaline. If you're unsure about the pH of your soil, or whether or not it is suitable for growing grape vines, it's a good idea to test the pH in the planting area.
Your local Extension Service may provide soil testing services or you can test soil pH yourself with an inexpensive soil pH tester probe. To raise the pH (make more alkaline) you can add pelletized limestone to the soil. To lower the pH (make more acid) you can apply Soil Sulfur, Aluminum Sulfate, or Chelated Iron. Adding organic compost to the soil at planting time and regularly as a mulch can also help to increase acidity and maintain acid soil conditions.
Learn More: What is Soil pH and How To Adjust It?
How To Fertilize Grape Vines
At Planting Time
At planting time, incorporate an organic plant food as directed on the label and/or or mix in some organic matter, such as composted manure or mushroom compost, at a 25% ratio to the native soil removed from the planting hole. Compost is especially beneficial to condition heavy clay soil that might retain too much water during the wet season and become hard as a brick during the dry season. Thoroughly mix the composted organic matter with the native clay at a 50/50 ratio.
When To Fertilize Grape Vines
Feed established grape vines in early spring when new growth begins to emerge and again about a month later, but do not fertilize past mid summer. Fertilizing too late in the season will promote new, tender growth that is susceptible to damage from an early frost or freeze, which can compromise the overall health of your grapevines.
Fertilizer For Grape Vines
In general, grapevines respond well to a well-balanced fertilizer such as 10-10-10. That said, whenever feeding plants that produce fruit that I intend on eating, I go the organic route and feed as directed on the product label with an organic plant food.
Additionally, I also mulch around the vine with a 2-inch layer of pine straw or shredded wood mulch. As these mulches decompose they add organic matter to the soil that your grapevines will love. Avoid using fresh sawdust or wood chips until they have cured in a pile for at least 6 months.
Note: Avoid over-fertilizing grapevines as too much fertilizer damages them easily. If you use an organic fertilizer there won't be the worries about burning your plants.
How To Water Grape Vines
Grapevines prefer a moist but well-drained soil. Though vines are moderately drought tolerant, they will appreciate moisture when there are grapes the vines, but not a constantly soggy or wet soil, which could be problematic.
At Planting Time
Immediately after planting your grapevines deep soak the soil in the planting area, including the root ball, to the depth of the planting hole. An application of Root Stimulator will provide an extra boost to stimulate early root formation and stronger root development. Root Stimulator reduces transplant shock and promotes greener, more vigorous plants.
During the First Active Growth Season
In average garden soil you should not have to water your newly planted grapevines every day. More often than not, this causes soggy or wet soil conditions that can lead to root rot and other plant diseases. In the absence of sufficient rainfall, water only as needed to keep the root ball and surrounding soil moist. Apply an organic mulch to help retain moisture and reduce hand-watering.
Keep in mind that deep soaking less frequently is much better than splashing just a little water around the vines every day. Grapevines planted during the winter dormant season, when not actively growing and evaporation has slowed, will require much less water. So, be careful not to overwater during winter!
Thereafter
When established, grapevines will require less water, however will prefer a consistently moist soil when there are grapes on the vines. Keep plants mulched well to help retain moisture.