February 7, 2020
“The juice of the grape is the liquid quintessence of concentrated sunbeams,” Englishman Thomas Love Peacock wrote 200 years ago. He was onto something. Grapes are wonderful for eating, juicing and winemaking, and they make beautiful ornamental plants. Late winter is the best time to plant grapes, when vines are dormant and available to purchase in bare-root form.
Grapes have been grown in California since the late 1700s, and thrived when varieties from Europe were introduced in the 19th century. These form the backbone of California’s grape industry, which produces more than 99% of commercially grown grapes in the United States. With some simple steps, you can enjoy these beautiful vines and fruit in your own garden.
Pick a grape best for Marin’s climate
You can find many bare-root grapes at local retail nurseries now. For good table grapes, consider: Thompson seedless (white), autumn royal (purple-black, seedless), catawba (red, aromatic), niabell (blue-black, excellent on arbors), Niagra (light green, good on arbors) and red globe (pink-red).
If you are tempted to try wine grapes, Marin’s warmer, northern interior portions are best. In milder, more coastal areas in Marin, fruit production will suffer from chronic pressure from powdery mildew and other diseases.Plant your grapevine in a good place
Grapevines prefer full sun, ideally seven to eight hours per day. If your site doesn’t get full sun, plant your grapevine where it will enjoy morning exposure.
Although grapes thrive in a wide range of soils, their roots do not like sitting in wet or damp soil. Plant them in an area with good drainage. On poor soil (such as clay that many of us have in Marin), add large amounts of compost into your soil before planting. Don’t worry if your soil isn’t perfect. The best wines often come from vines grown on less-fertile and even rocky soils. These produce smaller berries that contain a greater skin-to-juice ratio, ideal for winemaking.
Grapes need lots of space for good air circulation. Allow about 8 feet between each vine where soils are marginal, and up to 12 feet with deep, rich soil (if the soil is richer, the vine’s roots will spread farther, therefore they need more room). Vine spacing within the row can be 6 to 9 feet apart.
Grapevines require strong structures for support, such as a trellis, arbor or fence. If you have the space, an arbor may be ideal. It also doubles as an eye-catching focal point in a garden.
Proper care will help your grapevine thrive for decades
After planting, water well. Additional irrigation should not be required until you see 6 to 12 inches of growth. Once the vine is established, apply water deeply and thoroughly by filling the root zone, or you can install drip irrigation. Watering every two to three weeks is usually adequate under good soil conditions and a moderate climate. During hotter weather, water more frequently.
During the first year, no fertilizer is necessary. Thereafter, fertilize vines with nitrogen, zinc and potassium (generally do this in the winter, but follow the instructions on the fertilizer). In addition, on top of the soil, place a layer of mulch to keep moisture even around the vines.
After planting, let all shoots grow without pruning in the first year. After that, prune your vine in late winter to create a strong trunk. You will also need to prune to thin your crop, as vines too heavy with grapes will not produce sweet fruit and can be susceptible to disease.
In Marin, a common disease for grapevines is powdery mildew, which covers the woody stems and fruit with a powdery white fungus. Dusting your plant with sulfur can help. (Or try to buy varieties that are resistant to powdery mildew, such as niabell or Niagra). Another problem is bunch rot, which causes grapes to shrivel in late summer. This can be reduced by thinning berry clusters early and removing leaves around clusters to improve air circulation.
While grapes take about three to four years to mature, vines can last many decades. With proper care, your garden can produce beautiful vines and delicious grapes for years to come.
For more information, go to cagardenweb.ucanr.edu/Growing_Grapes_in_the_California_Garden.