4 Vineyard Maintenance 4.1 Maintaining Young Vines
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4 Vineyard Maintenance 4.1 Maintaining Young Vines Once the vine has been planted, (see 3.3 Planting growth where the cane is at least pencil thickness Grapevines) care must be taken to ensure a healthy 60 cm above the cordon, the vine can be tied plant. The first shoots from a young plant are down on the cordon. fragile. Each plant will produce a number of shoots The amount of fertilizer used in the second year is from the scion. Early careful removal of all ex- dependent on the growth in year one. The type of cept the single strongest most upright shoot will the fertilizer should be based on the soil analysis. help ensure a good start for the young plant. If the soil was balanced with amendments prior to Young plants should be protected with milk car- planting, minimal additions will need to be added. tons or plastic tubes, be kept weed free around the See 4.3 Nutrition for further reading. plant base and never suffer water stress. Water stress should not be considered for at least the Vine Rejuvenation first two years and sometime three depending on the strength of growth. Irrigation sets should be Severe winter temperatures (below -20°C) or very frequent and of short duration ensuring that cool temperatures during the shoulder season (be- there is always adequate moisture to a point just low -12°C) can cause substantial damage to the below the furthest extent of the rootzone. It is not fruiting buds of many varieties. If bud damage is necessary to irrigate well past the rootzone as this suspected, the severity of bud damage should be wastes water and leaches nutrients out of the assessed by bud dissection. Pruning methods should rootzone. be changed based upon the number of dead buds and the age of the vine. For mature vines more As the young plant grows tying should be done buds should be left in order to compensate for every 10 – 15cm of growth to help ensure a straight dead buds. On spur pruned vines it is important to and non damaged trunk. The vine is tied to a stake leave renewal buds below the cordon as it may be that is affixed to the cordon wire. If growth is slow, necessary to replace the cordon in the following removal of the axial shoots at the base of each leaf year if too many spur positions are lost. will encourage more growth. If the fruiting wood is severely damaged the trunk Continual monitoring for pests, disease and nutrient and the roots can still be functioning. A dead deficiencies will help the vine achieve its maximum fruiting structure can trigger very vigorous re-growth growth potential. Young plants should be included from the base of the vine and from the trunk area. in a standard mildew prevention program similar to adult plants. Cutworms can be a significant The objective is to absorb the strength of the root problem in young plantings and should be moni- system and create a new trunk and fruiting wood tored carefully in the first 3 years. capable of surviving through next winter. Excessive vigor produces canes that are particularly suscepti- See section 5.3 Pests and Diseases. ble to cold winter injury. Begin by removing the If the plant is grafted an inspection of each plant dead plant structure, although the dead trunk or should be done later in the season in both the first what remains of it could be used to train the new and second year to remove any scion roots having shoots. Allow most or all of the new shoots to grow grown past the graft. and tie them as with first year growth, ensuring a straight trunk for the future. Do not fertilize the The second year is much like the first year in plant as the growth will be very lush without any many respects. The vine is kept free of weeds help. Disease control for powdery mildew is very around the base, all trunk suckers continually important as the new growth is particularly sus- removed and treated as an adult plant for mil- ceptible. Water control may also be an option in dew and disease. If the cane has achieved at order to slow the growth and ripen the wood for least pencil thickness above the cordon wire, the winter.. vine can be tied to the cordon wire and 4 buds left below the cordon. In cases of exceptional 2010 Best Practices Guide for Grapes for British Columbia Growers 4-1 4 Vineyard Maintenance 4.2 Canopy Management for Pacific Northwest Vineyards Mercy Olmstead, Kathleen Willemsen, and Markus Keller can be used as an indicator of vine stress. Shoots Growing grapes in the Pacific Northwest can be originate from buds, which occur on canes, spurs, challenging and rewarding, and depending upon cordons; trunk and even underground (emerge as your location, vegetative growth and management suckers). will differ. Growers need to carefully assess their vineyard site including soil characteristics, annual Canes are mature, lignified wood from the previous precipitation, and precipitation timing in addition season’s growth. Canes and shoots are comprised of to researching potential grape varieties in order to nodes (Figure 4.2), with spaces between nodes assess potential vine vigor. defined as internodes. At each node is a bud con- taining three sets of buds (primary, secondary, and Vineyard location can have a large effect on vine tertiary). The primary bud is the most fruitful, growth. Those located in maritime climates may be while the tertiary bud is the least fruitful. Buds can concerned with controlling vegetative growth and be dissected before pruning to aid in determining increasing fruit exposure; while those in inland the potential crop load and help with decisions Pacific Northwest vineyards may need to adjust their about pruning severity. vegetative management to optimize their canopy and fruit exposure. However, proper canopy man- Pruning weight is determined by the amount of agement can lead to good profits for the grower and wood that is pruned off one vine in a single season. high quality fruit for the winemaker. This can be used in formulas to determine how many buds should be removed and/or left on the Management of grapevine canopies has changed over vine as part of balanced pruning techniques the years, and throughout the world. Many European (Reynolds, 1988). The amount of pruning wood is countries have adopted a tightly spaced, minimal determined by how the canopy is managed through- height vineyard, with no trellis support, while some out the previous season. Thus, if a vineyard is on a New World countries have moved to a wider spacing particularly vigorous site, then a large amount of and trellis system. Benefits can be realized for both pruning wood can be accumulated. However, on a types of systems, and those in between, depending low vigor site the canopy may be fairly small, upon grape variety characteristics and climate. leading to thinner canes and lower pruning weight. However it may behoove us to define some terms before talking specifically about canopy manage- Crop load is used to describe the ratio of yield to the ment for Pacific Northwest vineyards. pruning weight or leaf area. Potential crop yield before bloom can be determined by analyzing the Definitions of Canopy primary, secondary, and tertiary buds (Morrison, Components 1991). This can then be used to adjust the pruning strategy to achieve optimum balance for fruit quality. Canopy, as defined in this publication, contains all vegetative and reproductive plant parts that are The vigor of the vine describes the growth rate and above-ground. This includes the trunk, cordons, depends on a combination of factors, including soil canes, spurs (Fig. 4.1), shoots, fruit, and leaves. type, texture, depth, water availability, and variety The management of this canopy involves the ma- choice. Inherently, some grape varieties are more nipulation of these components in order to vigorous (e.g., Syrah or Shiraz, Sangiovese) than achieve a balance between vegetative and reproduc- others. Canopies of vigorous varieties can produce tive growth for optimum yield and fruit quality. an excess amount of leaf area when compared to recommended levels and may require more intense Shoots are comprised of vegetative and reproductive management. growth containing the length from the basal end to the growing tip. The growing tip is where leaves are Most canopy management is directed at the ma- initiated during optimum growing conditions, and nipulation of the canopy microclimate, which is the 4-2 2010 Best Practices Guide for Grapes for British Columbia Growers 4 Vineyard Maintenance Figure 4.1 A typical cordon-trained grapevine and its associated sections before spur pruning Figure 4.2 Shoot anatomy showing nodes, internodes, composite bud, and leaf scar. 2010 Best Practices Guide for Grapes for British Columbia Growers 4-3 4 Vineyard Maintenance climate surrounding and within the canopy synthesis requirement (Smart, 1988; Keller et al., (Tarara, 2005). Microclimate includes a number of 1998). For comparison, a bright sunny day in most factors including solar radiation, temperature, wind of the Pacific Northwest will have about 2000 speed, humidity, and evaporation rates. Because µmol/m2s, although this may vary according to your leaves tend to alter these factors, the canopy mi- specific latitude and time of season. Light quality is croclimate depends upon the number of leaves and also an important factor in plant growth, as leaves their spatial arrangement within a defined area strongly absorb at peaks in the blue (430 nm) and (Smart, 1985). red (660 nm) range . The range of the spectrum that plants use for photosynthesis is called photosyntheti- Goals of Canopy cally active radiation (PAR), which is approximately Management the visible light range from 400-700 nm.