Cane and Spur Pruning
With the 2011 vintage wines put to rest for the winter in the cellar, we have turned our attention to pruning our vines. Ask any vineyard crew and they will admit that pruning is a challenging process, but it plays a critical role in the creation of quality wine. Pruning involves the removal of growth on the vine and usually starts in January or February, and continues through harvest. By pruning after each harvest, we can control the size and shape of the vine. This optimizes production potential, maintains balance between vegetative growth and fruit production, regulates bud break, and can remove diseased tissue. In viticulture terms, there are four categories of pruning: vine form initiation, removal of the previous year’s growth, canopy management, and fruit thinning.
Vine Form Initiation
Although there are many types of vine forms, we typically use cane and spur pruning.
Spur pruning creates stationary “cordons” that are used year after year, whereas cane pruning uses last year’s growth to lay new cains. Spur pruning cuts back the previous years canes. An example of spur pruning can be seen in Figure One below.
Cane pruning uses one of the canes from the previous year as a source for the new growth. The cane pruning method is often more time consuming and can require special expertise. Because cane pruning allows more buds to remain and disperses the fruit-bearing shoots away from the crown of the vine, it is often implemented on varietals that produce smaller clusters (e.g., Pinot Noir, Chardonnay, and Riesling) or when a vine’s yield starts to significantly decrease in old vines. When selecting the cane, we look for one that is round, healthy, and at least ¼” in diameter. This cane is left on the vine during winter pruning, and then it is tied down in early spring. A benefit of cane pruning is that it can hinder the spread of infection, especially Eutypa. This devastating disease first attacks the canes or “arms” of the vine and eventually kills the entire plant, so it is important to avoid pruning during particularly wet months. When the previous year’s canes are removed, the infected part of the vine is removed before it has the chance to spread to the trunk of the vine infecting the whole plant. An example of cane pruning can be seen in Figure Two below. In 2006, Knights Bridge Vineyards was cane pruned to retrofit the old vineyard trellising.
Removal of Previous Year’s Growth
The removal of the shoots from the previous harvest is often done in late January and early February. Keeping the old shoots on the vine during winter helps to avoid the spread of disease and helps prevent frostbite in newly emerging buds. Pruning too early can allow moisture to enter the wounds, which can lead to an infection. Pruning also promotes new bud activity. Growers tend to wait until the end of January or the beginning of February to prune the old shoots in hopes that the new shoots will emerge in the middle of March decreasing the chance of winter frost damage. Frost at bud break destroys the buds of the plant, which house the clusters, thus significantly lowering the crop yields and quality.
Canopy pruning occurs after bud break, which usually happens in April and continues through harvest, and includes tucking and thinning canes, removing suckers, and thinning leaves. The growing canes are tucked behind the upper wires to help them grow upright and to allow the new shoots and fruit to receive more sunlight. At this time shoots are thinned, which opens the canopy for more sunlight and air circulation. Sucker (new plant material that sprouts on the trunk and cordons of a vine) removal keeps the vine from expending energy on extraneous growth.
Leaf thinning involves removal of leaves from vines, again opening the plants and fruit up to more sun exposure and airflow. This happens throughout the growing cycle until just before harvest. Leaf thinning just prior to harvest helps to ensure leaves are not in the harvested fruit. During the growth stage, the vines produce canopy and clusters, which mature through the stages of flowering, berry set, and verasion (the start of fruit ripening). The amount of air flow during the time of flowering is critical because too much wind can damage the flowering clusters, leading to poor fruit set and a decreased crop yield. Too little airflow through the rest of grape maturation can foster mold and bacteria damage of the fruit. Leaf thinning also regulates the sun exposure of the clusters. After verasion, this is monitored closely because crops can easily be damaged by overexposure and the value of the fruit can be harmed. When clusters are overexposed, there is a higher risk of sunburn, which damages the grape skins leaving them vulnerable to fungal infections, hinders the sugar accumulation of the berries stopping them from reaching full ripeness, and destroys the pigment in the berries causing less color extraction in the fermenting juice. At the same time, too little sunlight can cause vegetal off flavors called pyrazines, which develop in the berries and affect the aromas and flavors of the finished wine.
Fruit Thinning (“Green Drop”)
Fruit thinning often occurs before the grapes go through full verasion, and it removes the less ripe clusters. We believe that this allows the vines to concentrate all their energy on fully ripening the remaining clusters and helps to develop the complex flavors that characterize a finished wine. Regulating the overall yield of the vineyard prevents over-cropping of the vines over time, which causes a significant decrease in the quality of the grapes and shortens the life of the vines.
As spring arrives, the vines emerge from hibernation. It's a gorgeous time of year as the entire region undergoes a renewal.
However, it is no time to relax. The vines are at a crucial stage of development and frost is a major threat. Frost can damage or destroy the buds, which contain the embryonic grape clusters. Until these buds develop fully, frost remains a concern.
To deal with the threat of frost, we use wind machines. These machines use enormous fans that mix warmer air from high above the ground with colder air near the vines. Because temperatures drop at night, the fans must be turned on manually in the early morning hours - often at about 3am. These are early, cold, and loud mornings in the valley, but it is exciting to witness the start of a new vintage.
Bud break is when the vine comes out of its winter hibernation, and the leaves and embryonic grape clusters emerge. It is stunning to see the vineyard explode with activity in only a few short weeks. Eventually the buds flower and will go into 'full bloom.' At that point the young berries will be seen.
This is a critical time in the vineyard, as the new tender shoots are most susceptible to frost damage. The young budding tissue can freeze and we can lose most of our crop if that happens. Budbreak is highly dependent on soil temperature and the length of day. At Knights Bridge we usually see a soil temperature of about 60 degrees coinciding with bud break. During this time we will be on the lookout for certain pests in the vineyard, such as cutworm, Erineum mite, spider mites, and of course, mildew. At bud break we will spray an organic mixture commonly referred to as "Bordeaux mixture." This helps us get control over fungi like phomopsis and powdery mildew, in addition to lowering numbers of Erineum mite, also known as "blister mites," which can deform newly developing leaves.
There are also the ever-present worries of other mitigating factors outside our control throughout the growing season - frost, wind, hail, mold, and other natural factors that can destroy these delicate flowers. The life of a grape farmer is an ongoing balancing act between nature and nurture. From what we see in the vineyard this year, we are excited by the possibilities.
Blending the Perfect Cab
Winemaking is quite time-consuming. For instance, when putting together optimal blends, we start by having the winemaking team taste samples from each barrel.
We blend different blocks from the vineyard in our quest to find the perfect way to highlight all the amazing characteristics of Knights Valley. Each year is slightly different, the year's blending process is tailored to best convey how that particular vintage expresses the terroir of the region.
There is a consistent core theme to the red wines from Knights Valley: floral, violet, and lavender; dark-red fruit, blueberry, cassis, silky tannins, and a mineral finish. However, one year might find the violet standing out, whereas in another year the blueberry is intense. Blending helps us capture these vintage variations.
After final blends are determined, the wines are racked to tank just prior to bottling.
So you see, a winemaker's work is rarely, if ever, done. But here in Knights Valley, it always remains a labor of love.
August in the vineyard
Veraison marks the onset of ripening of the fruit, where sugars start to accumulate in the berries. For the red varietals the berries turn from green to pink, then finally to purple, whereas the whites go from green to golden. Due to the cooler weather and late season rains this year, we anxiously awaited the arrival of veraison in the vineyard. On average, white varietals start earlier and usually go through veraison more quickly than red varietals.
We have been tracking phenology points (bud break, bloom, fruit set, veraison and harvest) in the vineyard since 2007 and the recorded data helps to better estimate when harvest will occur.
Veraison Dates 2007- 2011
In 2011, we started to see veraison in our white varietals the first week in August, which is approximately 7-10 days later than what we consider normal. The reds began veraison the second week of August, which is about a week later than normal. These delays are attributed to the long, rainy spring and moderate summer temperatures so far this year.
During the time of veraison, we look for a large gap in the diurnal temperature (the difference in temperature from day to night). August had highs in the low nineties, with nighttime temperatures dropping into the upper forties. This diurnal temperature change plays out favorably for the development of complexity, and fosters even and complete ripening: the high daytime temperatures break down pyrazines (green flavors) and allows for sugar accumulation, while the low temperatures at night provide the vines a lower stressed environment in which to “rest”.
We will continue to track ripening as we get nearer to harvest
Climate in the vineyard
Each year presents different challenges in the vineyard, which is what makes farming and agriculture so interesting. Temperature is particularly important as it determines when the vine goes through its cycles, from bud break through veraison and harvest. Here at our vineyard in Knights Valley in Sonoma County, we pay a lot of attention to the weather, with two stations on the property measuring the climate at all times. The cumulative amount of heat available in the growing season is expressed as ‘Degree Days.’ To get a better idea of how we measure temperatures at the vineyard, please read our previous article on Degree Days [ http://www.knightsbridgewinery.com/degree-days ].
Grape quality is affected by many factors, including weather, soil minerals, acidity, time of harvest, and pruning method. All of these factors influence the vines, the way we farm, and our winemaking techniques.
Number of Degree Days at our Knights Valley vineyard
April 2008 – August 2011
Knights Valley, the warmest Viticulture Area in Sonoma County, has a historical average of 3,270 Degree Days. Tracking the variation in Degree Days helps to refine our understanding of what constitutes optimal days for future harvests. Cooler years, such as 2010 and 2011 (at least as of August), can lead to higher acids, crisp flavors and mid-palette structure, where as warmer years, such as 2008 and 2009, can lead to greater ripeness and round tannins.
In 2008, frost occurred in late spring, after bud break, which caused lower yields throughout Sonoma and Napa counties. The summer brought hot days with cool evening temperatures, resulting in ideal growing conditions. The number of Degree Days in 2008 were higher than average, at 3,638. We picked whites during the last week of August/first week of September and the reds in October.
The warm weather trend continued into 2009. Winter and early spring in 2009 were unusually warm and dry. Late spring rains were followed by warms spell in June and September. Nearly ideal weather allowed for the Sauvignon Blanc and Chardonnay to achieve perfect ripeness. They were harvested in the second and third week of September. Even with the early October rains, our Cabernet Sauvignon achieved 25 brix and was able to be harvested in excellent condition. With a warmer than usual year, Degree Days totaled 3,448 for 2009.
Despite the fact that globally 2010 was one of the warmest years on record, here in Napa and Sonoma we experienced a relatively cool season with an abundance of early rain as evidenced by the lower number of Degree Days (3,117). The last few weeks in August saw temperatures reached 100 degrees and above, causing some vineyards to lose crop; with high temperatures, the vines shut down causing dehydration of the fruit and there is greater risk of heat damage. An overall cooler season resulted in harvest being a month later than usual for Knights Bridge, with the whites being harvested the first week in October, leading to excellent complexity and beautiful balance.
So far, 2011 has shown a wet, long lasting spring with cool temperatures. We saw bud break in April (normal timing) and the yield so far appears to be normal. We’ll have a better estimate in the coming weeks. Fruit set looks even, though we did see some shatter [ http://www.facebook.com/note.php?note_id=252378988123185 ] on the Cabernet Franc and Malbec. The degree days are trending with 2010 so far, and assuming that stays on track, we expect to see rich, well-structured wines in this vintage.
Here at our Knights Valley vineyard we constantly monitor the vineyard throughout the growth cycle of the vine – from bud break in the spring, to leaf fall and then dormancy during the winter. Though we’re fortunate to have ideal temperatures and soil, there are risks throughout the growing cycle that we, as farmers, need to manage.
One of the more critical stages in the growth cycle comes immediately after flowering on the vine occurs. Typically happening in May or June, the fruit set provides the foundation for the size and quality of that year’s harvest.
Fruit set can be negatively impacted by weather that is too rainy, cold or windy, which can disrupt the pollination and fertilization. During these conditions, two issues can occur: Hens and Chickens and Shatter.
Hens and Chickens
Hens and Chickens (also known as millerandage) refers to a cluster of grapes that has small, stunted grape berries (referred to as chickens) alongside normal grape berries (referred to as hens). It is usually the result of cold weather or heavy, late season rains that occur just as the vine is flowering. Either winds and heavy rains wash away some of flowers, or pollination never occurs resulting in stunted grapes that will not produce the desired result and will thus decrease the overall yield for that year’s harvest.
Shatter occurs when pollination fails and thus grapes do not develop after flowering. It usually occurs as a result of a heavy rains or hail. It can also occur as a result of extreme temperatures, abnormally windy conditions or poor pruning practices. Shatter can have a severe impact on yields.
The challenge in the vineyard is to protect the fruit set from these external forces. Thankfully, we don’t see large fluctuations in weather patterns because our climate in Knights Valley is protected from the influence of the Pacific Ocean. When temperatures and weather conditions are ideal, we see normal fruit set where there is uniform grape size and limited uneven ripening, resulting in both higher quality and quantity at harvest – a blessing we don’t take for granted.
HISTORY OF KNIGHTS VALLEY
Situated at the foot of Mount St. Helena, just north of Calistoga, the beautiful Knights Valley holds a special fascination. For centuries, its sloping hillsides of native oaks, Madrones, Manzanita and its rich fertile valley floor was home to the peaceful Wappo tribe of Native American Indians who settled the area some 4,000 years ago and who referred to Mount St. Helena as Kana’mota – the “human mountain.”
In the early 1800’s, the Spanish began occupying the area and setting up land grants or ranchos. During this time 17,740 acres of Knights Valley and Franz Valley were deeded over to Jose de Santos Berryessa, and named Rancho Mallacomes. An adobe hunting lodge was built, becoming the first modern structure in the valley. Following the Bear Flag Revolt of 1846 (partially led by Thomas Knight, namesake of the Valley) and the Mexican War, California became a state in 1850. In 1853 Berryessa sold 8,328 acres of Rancho Mallacomes to settler Thomas Knight who planted vineyards, wheat, peaches, apples and raised sheep. He also built a sawmill on Kellogg Creek. The valley was given his name and he and his family lived there for over 20 years.
While some ventures failed in Knights Valley, growing premium wine grapes has been an ongoing success. Over the years, wine grapes not only helped preserve the valley’s natural beauty and agricultural heritage, they helped establish Knights Valley as a premier source of grapes for fine wines. By 1912, wine grapes were Knights Valley’s most planted crop and the quality of its fruit became legendary. For example, such great Napa Valley wineries as Chateau Montelena, Beaulieu Vineyards and Beringer all used Knights Valley grapes.
Today, the valley and vineyards of Knights Valley continue to inspire, producing world-class Chardonnay and Bordeaux varietals such as Cabernet Sauvignon and Sauvignon Blanc that consistently earn acclaim from critics and wine lovers alike. This special place continues to enshrine the rough beauty and ambition of the West, but contains within it a classic finesse and style that makes this one of the most unique wine-growing regions in the world.