Establishing Cold Hardy Grapevines on Spur Pruned High Cordon System
Vine Establishment
There is more than one way to train a grapevine, but cold climate grape cultivars are usually characterized by having a downward growing habit and high vigor and are thus better suited to being established on a high cordon training system. This instruction will provide guidance through the first few years of vine establishment in Northern climates. Prior to planting, growers should already have selected the appropriate cultivars for their climate and market, made any necessary soil amendments, and determined aspects of trellis design like planting density and fruit zone height.
Year One
During the first year, there are two clear main goals:
- Establish an extensive and healthy root system
- Grow shoots out to become the vine’s trunk.
Before planting
Grape cultivars ordered from plant nurseries are shipped as bare root cuttings, although some nurseries sell actively growing potted plants. If planting has to be delayed for a couple of days, make sure the roots stay moist, you can moisten the packing material around the roots or cover them with wet paper towels, place the vines in plastic bag, and keep in a cool storage area. Proper storage will prevent plants from molding and drying out so they are at prime health when planted.
Care for potted vines purchased before planting date to maintain plant health. Encourage shoot and root growth by removing all flowers/fruit.
Planting
During planting, vines that are not immediately planted should be kept moist. Double check the health of the vines before planting and only trim roots that are excessively longer than determined planting depth or are damaged. Dig a planting hole as deep and wide as the roots system of the vines. Plant vines deep enough so that the roots are below the surface of the soil. Cover the roots of the vines with the soil and tamp it gently to ensure good contact of the roots with the soil and to eliminate air pockets. Do not add any fertilizer, compost, or manure to the planting hole as it can burn new roots.
When planting potted vines, take caution to avoid knocking off any tender shoots. Untangle the root mass by teasing apart roots. If roots are not teased, the vine can become root bound, a state resulting from roots growing around each other, creating a knotted root mass rather than growing out into the soil. This often leads to weak plants with low structural integrity and eventual plant death.
Management
Thorough watering after planting is critical for the survival of the newly planted vines, as it will increase root contact with the soil. Weed control is a critical task during the first year of vine establishment; weeds are highly competitive for water and nutrients and will negatively affect growth and root development of newly planted vines. Monitor and control for insects and disease to protect vegetative growth and optimize the ability of the leaves to make carbohydrates for the plant.
Training
Allow for all of the shoots on the newly transplanted vine to grow out unless they appear to be suppressing the growth of lower buds near the base of the plant. This specific instruction contrasts other resources that recommend trimming the vine to 2-3 buds before planting. When more shoots are allowed to grow out it provides extra leaf area to produce more carbohydrates that will help develop a more extensive and healthy root system during the first year.
Training shoots upward to the first wire of the trellis is not always necessary during the first year. When shoots are trained upwards the overall leaf area of the newly established vines is less than when shoots are left to grow over the soil surface. However, weed and pest control are more difficult when shoots are growing over the surface area.
Fastening/training shoots along a vertical rebar will lead to straight shoots that can become the trunk. Options for fastening canes to rebar include using fasteners such as agriflex, hooked rubber bands, rubber string, or tapeners.
Note:
Vigor and Shoot Quality
Which shoots you select to become the trunk, cordon, spurs, etc. should be based on shoot quality. A “high quality shoot” is one that is fruitful and winter hardy. Overly vigorous shoots, often referred to as “bull canes,” lack these traits and are characterized by rapid growth, long internodes (the space between each bud), thickness bigger than a sharpie marker, and extensive lateral shoot growth- all of which are signs of poor shoot quality. The ideal shoot has the diameter of a pencil and internodes lengths approximately the size of a fist. Varietal vine vigor, soil fertility, and climatic conditions all influence vine vegetative vigor. To decrease the chance of growing vigorous shoots, avoid growing practices (e.g. unnecessary use of grow tubes) that encourage rapid shoot growth.
Year Two
The second year is devoted to growing vegetation only, in particular training the cordons or the arms of the vine. Training the vines during year two will be easiest if the vine trellis is installed with a proper trellis wire and possibly a lower catch wire for the purpose of maintaining efficient shoot positions.
During the dormant pruning period (usually late-February through mid-April), decide which vines grew healthy and tall enough to support the next training phase. Those vines that appear weak or are far shorter than the fruiting trellis wire can be cut back to a fewer number of buds and grown out again, repeating year one.
Creating a trunk
Choose two canes (one-year-old shoots) to become the trunk(s), but keep an extra shoot or two until bud break to assure that selected canes are free from frost damage. Clean up canes by removing last year’s tendrils and lateral shoots. Retain buds that break close to the fruiting wire (approximately the top 8-12 inches).
Training shoots
If possible, allow shoots to grow and be trained out with enough space between shoots to avoid potential shading problems (refer to vine establishment info graphic figure on page 14). Further into the growing season, prior to shoots becoming woody, train one to two shoots in each direction down the training wire to become cordons. Training two shoots on each side as potential cordons will provide additional options if one shoot is subject to frost damage. Leave other shoots, laterals, etc. on the vine until it is time for dormant pruning the following season. Pruning during fall can stimulate vine growth, which takes energy away from the plant becoming winter hardy. Refer to above paragraph on how to select a high quality shoot and for further recommendations on shoot selection.
Note: When securing shoots, resist wrapping shoots around the wire. This could can lead to the wire cutting into the vine, lowering its overall ability to function.
Management
Continue irrigating vines and controlling for weeds on the planting row as needed. Insect and diseases monitoring and control is critical to the successful establishment of vines during this second year period.
Year Three
After the cordons have been established, year three aims to grow out shoots from cordons and establish spurs: pruned canes that provide the buds from which the fruit bearing shoots will grow each year.
Establishing cordons
Prune last year’s tendrils and lateral shoots off chosen cordons similar to cleaning up the trunks in year two. Prune canes to a length that matches your planned vine spacing dimensions (i.e. if you plan to have six feet between vines, prune cordons to three feet or so on each side). If it is clear that only one of the cordons survived the winter, remove the other damaged cordon. If both are damaged, extra shoots that were kept on the vine the previous year can be carefully trained as a replacement. If there is any question about the quality of a chosen shoot, wait to choose the final cordon until bud break.
Management
Grow out shoots and follow canopy management tasks like combing (may choose to hoop under lower catch wire), leaf thinning, lateral shoot thinning, and skirting the vines as needed. Ripen no more than 1/3 of the vine’s total clusters to prevent over-cropping. If canes from year two are too weak, remove all clusters to encourage vegetative growth. As with year two, continue to weed and irrigate vine rows, protect vines from insects and diseases, and avoid fall pruning.
Year Four
This is the first year that the canes from each point along the cordon are pruned back to become spurs. The concept of a spur can be a little difficult to imagine for beginning growers, but keep in mind that shoots mature into canes, which are then pruned down to spurs that have a specific bud count. To make the spur, prune back each cane to 3-4 buds (recommended for cold climate cultivars trained on high cordon). The goal will be to grow out 4-7 shoots per foot- shoot count being dependent on the cultivar’s fruiting capacity and overall vigor. Always keep shoot density in mind when deciding how many spurs and buds to keep on each cordon.
Management
After bud break when shoots reach 5-12’’, roughly reduce shoot count by removing shoots to the determined density. Allow the vine to mature a full crop, or thin fruit to two clusters per shoot for heavy bearing cultivars (e.g. ‘Frontenac’). Keep up annual tasks of thinning lateral shoots and leaves around fruiting zone, combing, skirting, and monitor and control for pests and diseases.
Year Five and Beyond
At this point, the grapevines should be fairly established to produce good quality fruit for years down the road. Beyond summer canopy management tasks described for earlier years, other practices for monitoring and repairing the health of the grapevines and thus prolonging high quality fruit production include:
- Grape bud analysis- checking buds on the first 5 nodes from the base of the canes to assess cold damage during winter.
- Spur renewal- as vines and spurs get further away from the cordons, spurs need to be renewed to bring the centers of growth closer to the cordon. Always choose the canes on the lower portions of the spurs over those that are higher and further away from the cordon to become the current season’s spur.
- Pruning weights- while this practice is tedious, obtaining a rough weight for pruned, one year-old shoots can indicate vine vigor and fruiting capacity. Vines that have been over-cropped will have low pruning weights, opposite to those that have been under-cropped, which will have high pruning weights.
- Cordon extension- it is common for shoots to not grow to their full trellis length by the second year. Cordons can easily be extended by training shoots that break near the end of the cordon horizontally along the wire.
