Preventing spur creep for cold climate grapevines

Authors: Madeline Wimmer, Soon Li Teh, John Thull

When working with spur-pruned grapevines in cold climates, the spurs—the regions where fruit-bearing shoots emerge—are originally created by shortening canes originating from a young cordon (i.e., the arm(s) of a grapevine). Overtime, these original spurs support newer spurs that stack on top of the older spur region year after year, and this can lead to what is known as spur creep, when a spur becomes long, old, and less productive.

Why is spur creep a problem?

As spurs continue to age, they can accumulate damage from cold temperatures, similar to cordons, and become less productive over time. Additionally, the longer they grow, the less room there is for the current season’s canopy, which is especially true for Vertical Shoot Positioned (VSP) grapevines that have less canopy area, overall.

Spur creep can leave portions of the cordon blank, as they become unproductive, and can be worsened if growers heavily thin away all the non-count shoots that emerge from the cordon when spur replacement is needed.

Older spurs can additionally lead to irregular shoot growth. This can complicate future pruning and vine management. The unbalanced canopy may ultimately result in uneven fruit ripening. Extreme spur creep can lead to wider fruiting zones that are harder to expose properly and harvest efficiently.

Preventing spur creep

There are a few things that growers can do to prevent spur creep including:

1. Create spurs from canes that are positioned closest to the cordon.
2. Manage vines to prevent bull cane growth.
3. Allow some shoots to grow from the cordon (non-count shoots) where old spurs exist.
4. Prune out old, long, unproductive spurs and replace them with fresh canes originating from the cordon.
5. Use sharp pruning tools and follow other best pruning practices for good results.

Below, we’ll briefly cover how each of these steps help to prevent spur creep.

1. Make spurs from canes that are closest to the cordon.

During the first year a spur is created, a cane is cut back to 2-4 nodes (i.e., slightly swollen regions along the cane where dormant buds exist and shoots emerge). By the following growing season, there will be between 2-4 canes originating from that spur, but only one of these canes is needed to create the new spur for the next growing season. When possible, select the cane that is healthiest and closest to the cordon and remove the rest, unless more are needed for a specific situation.

Image: A close up of a High Cordon (HC) trained grapevine cordon with successions of wood to show one-year-old canes, two-year-old canes that were cut back into spurs, three-year-old canes, and the original four-year-old cordon. Options to renew this three-year-old spur region include cutting back the fresh one-year-old cane that emerged from the cordon, and then removing the old spur at the base of the cordon).

2. Manage vines to prevent bull cane growth. 

Bull canes are fast growing shoots that have oblong and thick circumferences, and are known for having long internodes. These long internodes contribute even more length and potential for spur creep. Bull canes are also generally less winter hardy, making them susceptible to winter injury over time. For high-vigor vines, practicing balanced pruning and leaving more shoots on a grapevine can help prevent overly vigorous growth and bull canes. Avoiding practices like over-fertilizing with nitrogen, can also help.

Image: A young grapevine showing a spur that was originally made from a bull cane. Note the long internodes on the cane in the upper left corner of the photo. In this scenario, replacing the bull cane spur with a healthy cane nearby is recommended.

3. Allow some shoots to grow from the cordon (i.e., non-count shoots) where old spurs exist.

Most grapevine varieties will grow shoots opportunistically from the cordon, which will lead to more shoots in a canopy than estimated during pruning. Many of these shoots do not produce fruit when emerging from the cordon and are often removed during early season shoot thinning, but it can be helpful to retain a few if you notice them growing near old spurs. These can then be saved as replacement spurs during the following winter pruning season.

4. Prune out old, long, unproductive spurs and replace them with fresh canes originating from the cordon.

Similar to old cordon wood, old spurs can undergo injury from extreme cold and other adverse conditions, and overtime benefit from replacement. When good replacement options are available, prune old spurs with a clean cut near the base of the cordon (but leaving somewhat of a stub to ease the vascular dieback that occurs within the cordon), and then cut back a nearby cane to the intended spur length .

Image: A mature grapevine cordon trained as Vertical Shoot Positioning (VSP) where a large, old spur is ready for removal in the center of the canopy. The person pruning this vine could choose to continue making a spur from the cane growing out of the top of the spur, but this would continue the creep. Alternatively, it would be recommended to choose one or two of the canes originating from the cordon to prune back into a new spur, and then remove the old spur near the cordon.

5. Use sharp pruning tools and follow other best pruning practices for good results.

Sharp, clean pruning shears and loppers are essential for making precise cuts and minimizing wounding during pruning. Additionally, follow other best practices for pruning, such as avoiding pruning before an extreme cold temperature event.
How can you correct spur creep in established vines?

To learn more about caring for pruning tools, check out this UMN Fruit and Veg article, "Caring for winter pruning tools." 

If your vines are already experiencing spur creep, consider taking the following steps:

• Identify cordons, or sections of a cordon with unproductive or overly long spurs.
• Remove older spurs when there is a new cane that has emerged from the cordon that can replace it. During the growing season, focus on retaining renewal buds closer to the cordon near old spurs.
• Replace heavily damaged or unproductive cordons by laying down a new cane and removing the old cordon. It can also work to lay down two canes and prune off the lesser performing cane part-way through the growing season.