LSU AgCenter's Weekly Message

We Can Grow Bunch Grapes with Good Variety Selection and Some Effort

When you think about bunch grapes, wine grape varieties like Chardonnay and Merlot or table grapes like Thompson Seedless may come to mind. There are reasons that we don’t grow these (at least not for long) here in the Deep South. Something called Pierce’s disease, which is caused by the bacterial pathogen Xylella fastidiosa, limits what types of grapes we can grow.

As you might imagine, muscadines are resistant to Pierce’s disease. Some bunch grape varieties have this characteristic, too.

While resistance to Pierce’s disease is the first hurdle to overcome, a number of other diseases also cause problems on bunch grapes. These can be managed to some extent, but choosing varieties that are less susceptible to them is also important.

Blanc du Bois is probably the variety most widely grown for white wine production in the Deep South. It is, however, highly susceptible to the fungal disease anthracnose and requires regular fungicide applications not only to produce high quality fruit but to survive in the long-term.

A grape that tends to survive without quite as much care is Black Spanish or Lenoir, though disease management will still be necessary. This is grown primarily for making red wine.

Another red wine grape is MidSouth (pictured right). Grape expert Dr. Eric Stafne of Mississippi State University is a fan of this one. He’s found that it’s one of the best as far as survival goes. A downside of this one is that it’s not very easy to find to purchase.

Norton or Cynthiana is widely grown as a red wine grape in some parts of the South, but it’s better suited to north Louisiana than south Louisiana.

Even with good variety selection, bunch grapes still require more effort (especially fungicide applications) to produce healthy fruit than muscadines do.

Plant grapes in a well-drained, sunny location. Bunch grapes are not quite as vigorous as muscadines, so while a 20-foot within row spacing is typically recommended for muscadine vines, you can space bunch grapes about 7 to 8 feet apart.

A trellis with a single 9 or 10-gauge galvanized steel wire 6 feet from the ground is appropriate. Another wire can be placed 1 foot from the ground so that you can attach a drip irrigation line, if desired. Posts can be spaced approximately 21 to 24 feet apart so that there are three vines between each pair.

Plant bare root plants in the winter, while they’re dormant. You have more flexibility when planting containerized plants, but late winter is good time to plant them, too, if they’re dormant. Place plants at the same depth they were at in the nursery or container. If they’re grafted, make sure that the graft union is about 2 inches above the soil.

You can use a stake (e.g., of bamboo) or string suspended from the trellis wire to guide the vine towards the wire during the first growing season. When the vine begins to grow, choose one healthy shoot and remove the others. (Continue removing other shoots as the season goes on.) Gently attach the vine to the stake or string as it grows.

If the vine reaches the top wire during the first growing season, you can allow it to send a shoot in each direction along the wire. You may need to pinch or cut it a couple of inches above the wire to encourage it to send out lateral shoots. If it does not reach the wire during the first season, cut it back while it’s dormant and repeat the process of training up a trunk during the second season.

How to prune mature vines is beyond the scope of this article, but be aware that vines need to be pruned every winter, while they’re dormant.

Keep grass and other weeds away from the trunks, especially while vines are young. One-quarter pound of a fertilizer such as 10-10-10 can be spread after vines begin growing in the spring and again in 6 weeks. Keep fertilizer about 1 foot away from the plant. The amount of fertilizer can be increased the second year.

Let me know if you have questions.

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Dr. Mary Helen Ferguson is an Extension Agent with the LSU AgCenter, with horticulture responsibilities in Washington and Tangipahoa Parishes. Contact Mary Helen at mhferguson@agcenter.lsu.edu or 985-277-1850 (Hammond) or 985-839-7855 (Franklinton).