This article assumes some level of familiarity with cane and cordon pruning techniques.  If you are not familiar with the differences between cane and cordon pruning, it may make sense to review my prior posts on those subjects:

http://blog.vinestowine.com/2010/02/05/grapevine-cane-pruning.aspx

http://blog.vinestowine.com/2010/01/05/cordon-pruning.aspx

Cordon training/pruning is popular for its simplicity.  It takes less time than cane pruning and does not require a very skilled worker; therefore it is less expensive. 

However, cane pruning is preferred to cordon pruning because the selection of which cane and the cane length by a skilled vineyard worker can fine tune the balance of each individual vine better than cordon pruning. 

Additionally, cane pruning can improve yields.  The buds on a cane tend to be more fruitful than the buds of spur positions on a cordon.  When cordon pruning, only basal buds of the prior year’s canes are left to grow in the following season, whereas in cane pruning, a longer length of cane is left.  Although varietal dependent, these apical buds tend to be more fruitful than basal buds. This is especially true as vines age. 

Cane pruning also spreads the following season’s shoots out, requiring less suckering in the spring.  Only one shoot grows per bud or position along the cane, whereas two shoots grow from a traditional cordon’s spur position.

Many older cordon-pruned vineyards suffer from serious loss due to dead spur positions and arms from Eutypa or Bot canker. 

Between yield loss from Eutypa and lowered yields with older cordon vines, many growers are converting their cordon-trained vineyards to cane pruning.  By doing so, it is possible to cut out most of the cankers in the vines.

The best way to do this takes a couple years.  In the first year, a sucker from the base of the vine (but above the graft union) is selected and maintained throughout the growing season.  During pruning, this sucker is pruned back so that it is as tall as the fruiting wire, and the lower part can be dis-budded allowing only a few top buds to grow the following season to produce 3-4 shoots.  The rest of the vine is pruned normally this year.

This method may crowd the fruiting zone near the head of the vine during the second year, but it causes no loss of productivity. The following winter, the sucker will now be a replacement truck with 3 to 4 canes growing out of the top that can be used as canes.  The old cordon and the trunk can be removed to a few inches above the new replacement trunk.  The replacement trunk can be tied to the vine stake and canes can be selected and tied to the fruiting wire.

Some vines may not push a sucker in the first year, but will do so in the second year.  Also, some growers may not have the patience to do this over two years.  If vines push a strong sucker in the second year, or year one for the impatient grower, that sucker may be long enough to serve as the trunk and a cane the following season.  If not, it can just be used as a trunk, and the following year it will produce canes, causing only a one-year loss of productivity.

As an example, in this photo, after year one, a strong sucker was selected and used as a trunk and a cane, and the old cordon and trunk were removed to just above where the sucker emerges.  The vine had lower productivity, but no loss of productivity.  When we prune it this year, we will cut the sucker down to the fruiting wire to be a trunk and use this year’s shoot production to select two canes. 

If you do not want to wait two years, then the entire vineyard can be converted like this as long as the majority of vines have strong suckers selected in year 1. 

Without waiting at all, a cordon can be cut back to one or two spur positions and a cane can be pulled down and tied to the wire from one of these first spur positions.  Two positions per cordon should be left if you want two canes from each side for very vigorous vines, or only one position per cordon will be sufficient if two canes will be used.  The problem with this is that you may not cut the canker disease out if it has moved into these remaining spur positions near the head of the trunk.  Also, older spur positions tend to be long, and you may need to bow the cane to get it to tie back down to the fruiting wire.  With a really long spur position, the new cane may be bowed significantly and may bend under the weight of the fruit during the growing season.  A new fruiting wire may need to be added near the top of the spur positons.

Here is an example of vigorous Sauvignon Blanc vines that had significant Eutypa and low yields. It needs 4 canes to be balanced, so two spur positions were left on each side of the vines.  One cane on each side is bowed and tied down to the fruiting wire.  The other cane is tied to the first set of moveable catch wires.  If the grower continues with this conversion, they will likely add a new set of two fruiting wires near the top of the spur positions so that all four canes can be tied at the same height and rest along secured fruiting wires in a split canopy system.

These conversions can be expensive, requiring vine surgery and in some cases, additional wires or trellis modifications.  If canker diseases are not a major issue, but low yields are, and a desire to cane prune exists, there is the ‘mini-cane’ conversion below.  In this instance, a short cane is selected from about every third spur position and tied to the first catch wire.  This will not cut out any canker diseases though.  This requires no trellis wire and no surgery, although you may want to consider removing the spur positions in between the canes or at least disbud them, or you can remove them during suckering.

In all cases, it still makes sense to seal pruning wounds with a sealant such as B-lock to protect them from canker diseases.  This is especially true if you are performing vine surgery and making large cuts.  It is also recommended to do this type of surgery late in the winter once most fungal disease spores are already dispersed.  And it probably makes sense for new vineyards to be trained for cane pruning so that a time consuming and costly conversion is not needed later.

Email or call me if you want to discuss the best way to make a conversion in your vineyard.  All these methods have their pros and cons.