Grapevine cold hardiness
Grapevine bud cold hardiness is a dynamic process and changes throughout the dormant period as shown in Figure 1. Beginning in late August, as the vine prepares itself for dormancy, the tissues begin to acclimate. This is a gradual process and in V. vinifera, acclimation is in response to shorter day length and cooler temperatures. It is complex in nature and involves many factors and mechanisms. As temperatures drop to sub-freezing levels, the vine becomes more cold tolerant and achieves maximum cold hardiness during the coldest periods experienced mid-winter. Once temperatures begin to increase and the vine has achieved all of its requirements to break dormancy, it will begin to deacclimate. The effects are basically the reciprocal of those associated with acclimation as it is the transition from a cold hardy to cold tender state as a vine prepares to resume growth. As shown in Figure 1, deacclimation is more rapid than the acclimation process.
Susceptibility to cold injury
Grapevine tissues vary in their tolerance to freezing temperatures. Woody tissues of the trunk, cane, and cordon generally have higher tolerance than dormant buds or roots (Howell, 2000). Wample et al. (2000) found that phloem was most susceptible to cold injury followed by older xylem, younger xylem and vascular cambium. In terms of dormant buds, primary buds are the most susceptible to cold damage followed by the secondary buds and tertiary buds.
Howell, G.S. (2000) Grapevine cold hardiness: mechanism of cold acclimation, mid-winter hardiness maintenance, and spring deacclimation, in: RANTZ, J.M. (ed.) Proceedings of the American Society for Enology and Viticulture, Seattle, WA, 35–48.
Wample, R.L., G. Reisenauer, A. Bary, and F. Schuetze. (1990) Microcomputer-controlled freezing, data acquisition and analysis system for cold hardiness evaluation. HortScience 25:973-976.
Acclimation – complex process during which plants develop cold tolerance. It begins during late summer when shoots stop growing and become brown and woody or “harden off”. Tissues acquire increased cold hardiness through a number of factors and mechanisms. V. vinifera grapevines acclimate in response to both short days and low temperatures.
Advective freeze – is characterized by a massive passage of cold air during which little stratification of air temperature occurs with elevation changes.
Bud – compound structure from which shoots arise from in the spring. Fruiting buds are composed of large central primary bud, a smaller secondary bud and even smaller tertiary bud. Generally the primary bud is the most fruitful but often the least winter-hardy.
Cane – a mature woody shoot (one year old wood).
Cold Hardiness – is the ability of grapevine tissue to survive during exposure to low temperatures.
Cold/Winter Injury – is the killing of some part of the vine by low temperatures.
Cold Tolerance – see cold hardiness.
Cold Avoidance – is a strategy to survive cold injury by not being exposed to it. These include proper site selection as well as freeze protection strategies such as the use of wind machines or burying of canes.
Deacclimation - is the process when grapevines lose hardiness and are ready to resume growth. It is the transition from a cold hardy to a cold tender state.
Dew (frost) Point – is the temperature at which water vapour in the air condenses from a gas to a liquid. It is an important concept in the sense that when the dew point is below critical damaging temperatures, grapevine tissue can be more susceptible to cold injury.
Differential Thermal Analysis (DTA) – is a technique to conduct research on the mechanisms of freeze tolerance and also to predict lethal freezing temperatures for grapevines. Temperature differences are recorded between grapevine tissue and a reference over time under identical thermal cycles. Differential temperature changes over time provide data about when freezing events have occurred to grapevine tissue.
Dormancy – time between the end of commercial harvest and bud break with absence of visible growth.
Double pruning – extra buds are retained after an initial pruning early to mid-winter. A second pruning is done after assessing bud damage and the threat of frost injury is minimal.
High Temperature Exotherm (HTE) – heat released when supercooled water freezes extracellularly (in the intercellular spaces); extracellular freezeing is considered non-lethal.
Kicker cane – extra cane(s) retained during dormant pruning for subsequent removal during the growing season.
Lignification – is the process where vine organs accumulate lignin which allows more resistance to cold and water loss. Lignin is incorporated into a complex tissue called periderm on the surface of grapevine canes.
Low Temperature Exotherm (LTE) – heat released when supercooled water freezes intracellularly (within the cytoplast & vacuole); Intracellular freezing is lethal.
LTE 10 – is the temperature at which 10% of the primary buds will be killed
LTE 50 – is the temperature at which 50% of the primary buds will be killed
LTE 90 – is the temperature at which 90% of the primary buds will be killed
Periderm – bark which is thick waxy and brown that consists of phellogen (cork cambium), phellem (cork) and phelloderm.
Phloem – vascular tissue that transports sugars and other solutes throughout the plant.
Pith – central part of cane.
Radiational freeze – occurs when freezing temperatures develop during calm and clear sky conditions. Radiant heat is lost from the earth because there is no cloud cover to trap radiant heat or wind to mix the air. This results in very cold conditions at the surface.
‘Spare Parts’ viticulture – the use of multiple trunks, retaining suckers, double pruning to compensate for any winter injury that may have occurred.
Spur – a short cane pruned to 1 to 4 nodes.
Supercooling – the ability to withstand very low temperatures where the contents of the cell can remain liquid during subfreezing temperatures. Buds supercool to avoid freezing injury.
Temperature Inversion – is the reversal of the normal behaviour of air temperature in which a layer of cooler air at the earth’s surface is overlain by a layer of warmer air. Under calm, winter conditions, ambient temperature is warmer above the ground than at the surface.
Vascular cambium – tissue of canes and older wood that generates new phloem and xylem annually.
Xylem – vascular tissue that primarily transports water and minerals.
Best Management Practices for Reducing Freeze Injury
Economic Impact Analysis
Goodman School of Business Consulting group's Economic impact assessment of VineAlert
Wind Machine and Cold Injury Information
Dealing with Cold Injury in Grapevines
Research Updates and presentations
CCOVI Lecture Series
Regionally specific data
Grapevine Cold Hardiness Networking
Pacific Agri-Food Centre: Agriculture and Agri-food Canada
Washington State University
Niagara Sub-Appellation Boundary Descriptions
- Short Hills Bench is the most easterly of the sub-appellations located within the Niagara Escarpment. It encompasses the land rising up from the plain of the peninsula (south of the Regional Road 81) to the Escarpment Brow and situated between Twelve Mile Creek and Fifteen Mile Creek.
- Creek Shores is rich in waterways, and with Lake Ontario to the north, Twelve Mile Creek to the east, Twenty Mile Creek and Jordan Harbour to the west, is almost surrounded by water. Temperatures are well moderated with gradual spring warming and bud break.
- The Lincoln Lakeshore runs along the Lake Ontario shore from Winona Road to Jordan Harbour and Twenty Mile Creek, and is backed by the foot of the escarpment bench on its south boundary. Characterized by numerous seasonal streams and long gentle slopes that grade northward from the Lake Iroquois Bluff, the appellation is greatly influenced by the Lake Ontario
- The Twenty Mile Bench stretches east to west from Fifteen Mile Creek to west of Cherry Avenue. Bisected by Twenty Mile Creek, it has a complex topography with a distinctive double bench formation west of Twenty Mile Creek, and short, varied slopes that roll to the brow of the escarpment.
- The Beamsville Bench, running from the creek gully just west of Cherry Avenue to Park Road west of Beamville, is the narrow plateau sloping gradually from the cliff of the Niagara Escarpment northwards to Regional Road 81, marking the bottom of the crescent-shaped Lake Iroquois Shore Bluff.
- Vinemount Ridge lies just above and south of the brow of the Niagara Escarpment. This appellation covers two prominent geological features - the Fonthill Kame to the east and the Vinemount Moraine on its western edge.
- The Niagara River appellation is a small strip of land running along the river from John Street to Dee Road and inland approximately one kilometer. Soils in the area are primarily stratified fine sands, providing natural drainage and strong encouragement for vines to develop deep root penetration.
- St. David's Bench lies 10 km south of the shore of Lake Ontario and several meters above the Lake Iroquois Plain. The appellation follows the contour lines that define the escarpment from the Niagara River to Beechwood Road, with a complex topography.
- Four Mile Creek is the fertile plain that makes up central Niagara-on-the-Lake. It lies slightly inland from the lake and below the bench of the Niagara Escarpment providing for warm days and cool nights during the growing season.
- Niagara Lakeshore follows the shoreline of Lake Ontario from the Welland Canal east to the Niagara River and inland for approximately 3 kilometers. The primary influence on this appellation is the proximity of the Lake and its year round moderation of temperatures.
NOTE - Niagara sub-appellation boundary descriptions have been sourced directly from the VQA Ontario website: http://www.vqaontario.com/Home