Sara Williams and Bob Bors
Watering grapes is critical during their first year or two, until their deep and extensive root system develops. Then plants will need little supplemental water unless it is very dry. If soil fertility is poor, top dress them with an organic mulch a few inches deep applied to a metre diameter around the base of the plant. Grapes have few problems although powdery mildew and spider mites are sometimes present.
There are many ways to train grapes. To shade a low deck or a patio, using a trellis-like structure, and use ‘Valiant’. Highly ornamental, it will provide shade, but may not produce the highest quality grapes as many will be shaded.
To build the trellis, use heavy gauge wire with metal or wood fence posts. Place the posts a meter or two apart with the grapes planted between the posts. Using a few wires makes pruning easier than growing vines on a chain link or deer fence or other more complicated structure.
World-wide, the “Four Arm Kniffin System” is the most popular method, with parallel wires at 3 and 5 feet above the ground. The vine has a single trunk with four arms.
An alternative system better suited for the prairies has permanent arms on a low wire that is easily insulated in winter with natural snow accumulation or by covering it with loose straw just after freeze-up. This system has wires at 1, 3 and 5 feet. New growth is initiated each year from 2 arms on the bottom wire and grows up to the top two wires. With such a system, zone 4 grapes might survive in zone 3!
About 90% of a grape’s total biomass can be removed annually. Do not prune them while the sap is running in spring as they will “bleed” for several days, wasting sap full of sugar, carbohydrates and other nutrients that should be going into the formation of fruit, leaves and shoots.
1st Year: Allow the vines to grow with no pruning to encourage maximum root establishment. Lift any vines crawling on the ground onto the trellis, fence or other support.
2nd Year: Growth will be very fast. Prior to spring, select a healthy “cane” (grape talk for an individual vine) to be the future trunk. Remove all other canes. If long enough, tie it to the lower wire and trim away most of the buds above that point. If no canes are long enough, cut a healthy one back to about 4 or 5 buds. The topmost bud will usually grow most vigourously, but if after a few weeks a lower cane appears healthier, let that one become the trunk. Once the trunk is long enough, secure it to the bottom wire. Some growers pinch the main trunk once it reaches the bottom wire to encourage buds to break and make new canes, two of which are selected and tied along the bottom wire.
Shoots often emerge from the ground. Keep one or two of these to serve as backups for the new main trunk. But regularly trim them to only a few nodes so they do not compete with the trunk.
3rd Year: During the winter, cut back each arm to about 10 buds. Also leave two renewal spurs closer to the trunk. Renewal spurs are young canes that have only 2 buds. They will develop new wood to be used the following year to form the new arms. Fruit production usually begins during this third season.
4th year and beyond. Train each arm to have 6 or 7 young canes (produced the previous season) that are each only about 3 or 4 buds long. Prune back the vines to new wood as close as possible to the arms annually. Picture a candelabra that holds 12 candles. The “candelabra” would be the permanent trunk and arms; the “candles” the young canes with a few buds.
As the season progresses, canes should be encouraged to grow onto the upper wires. They will be easier to prune if simply draped onto the wires. If fastened or tied to the wires, they would need to be unfastened at pruning time.
Grapes sometimes generate “bull canes”, one half-inch or more in diameter with 5 or 6 inches between nodes. These generally remain vegetative with poor yields and are best removed.
Enjoy!
Sara Williams and Bob Bors are co-authors of Growing Fruit in Northern Gardens.
This column is provided courtesy of the Saskatchewan Perennial Society (SPS; saskperennial@hotmail.com). Check our website (www.saskperennial.ca) or Facebook page (www.facebook.com/saskperennial) for a list of upcoming gardening events.
