If your grapevines are planted in a sheltered area, and they don’t suffer from significant wind chill, then you may not need to water them every day. Young vines have shallow root systems and can dry out quickly. If the soil can go completely dry, the vines will stop growing until sufficient water is available. This can be severely detrimental when temperatures are below freezing or when you’re trying to protect your vines with a layer of mulch. In these cases, it’s essential to maintain constant moisture in the soil around grapevines by watering every day if necessary.
Vine roots require adequate oxygen for good health, so it’s important not to overwater in vineyards or areas of drainage. Grapevines in containers do not have access to oxygen, and overwatering is a common cause of the death of vines grown in containers. When water first comes out of the ground, it contains dissolved oxygen which gets used up as it seeps through the soil. If you are using sub-surface drip irrigation, make sure that you install emitters throughout the drip line because grapevines will use this water quickly if only one or two emitters are installed under each vine.
Watering frequency for grapevines differs depending on your location and microclimate. A good rule of thumb is to water young vines every day during hot weather but decrease to every other day after they reach 10 gallons in size if they are well sheltered from wind chill. During periods where temperatures remain below 40, you may need to water more frequently and increase the amount of water applied. This is especially true for vines that are not mulched with a dust mulch or Grow Blanket after planting.
Aeration with a garden hose at least once per week will help reduce compaction caused by foot traffic around grapevines (and any plant, really). It’s also important to prevent weeds from competing for moisture and nutrients, so keep the ground clear of weeds as much as possible until grapevine root systems have developed enough to outcompete anything growing nearby. Mulching your vines with a 3″ deep layer of organic matter helps control weeds, preserves soil moisture, and minimizes temperature fluctuations near the vine trunk.
How to water your grapevines
Did you know that grapevines are among the most thirsty of all cultivated plants? They get their water from rainfall, but they can’t get enough of it. Too little water is disastrous for these heavy feeders, and too much water will drown them. The challenge to the home gardener is how to provide adequate water during dry spells while minimizing damage when there’s excessive rain.
Grapes are best planted on a slight slope to be watered by gravity rather than sprinklers or drip irrigation, which can wash out newly formed roots on level ground. If you live where summers are hot and winters are cold, plant grapes against a wall or fence that offers protection against winter sun and summer heat. A quick-growing vine-like ‘Concord’ or ‘Niagara’ can be grown on a spacious arbor, but if you want to grow grapes over an existing structure such as a deck, remember that grape roots will eventually damage the decking and interfere with proper drainage.
Grapes need plants at least 8 inches deep to prosper. That means you either need sandy soil or no-dig landscape fabric at least 10 inches down before you put in rocks or sharp sand for drainage. The other obvious requirement is sun exposure, but not too much sun—grape vines abhor hot afternoon sun reflected from a south-facing brick wall. On a flat site, place the vines against a north-facing wall where they’ll get early morning sunshine and shade during summer’s peak heat. Where there’s no good sunny spot, grow grapes in containers on decks or patios (see Homeowner Tip #2).
Grapes need plenty of fertilizer. Most soils in the East are too acidic for grape production. Grapevines often show acid deficiency symptoms long before they reach their productive years—even when grown in neutral soil amended with dolomite lime. If you’ve ever seen yellow leaves (chlorosis), then look at your soil pH to see if it’s below 5.5—the lower, the better, so most grapes will produce well with little additional treatment beyond regular fertilization with an acidic fertilizer like Rose Tone™. If your soil is alkaline above 6.0, add sulphur monthly beginning the spring after you plant and continuing every month until the end of August to lower soil pH. If you’re growing grapes in containers, use a low nitrogen, high phosphorus potting mix that contains dolomite lime.
Grapes don’t like wet feet. Mounding up their planting area with additional soil, so there are at least 8 inches between the top of the root ball and the surface is an excellent way to prevent soggy roots after heavy rains or irrigation.