Most visitors are curious about the vines themselves and how they are tended. Viticulture is a complicated and expanding field of study, with many methods and preferences, but I'll offer a quick summary of my practice....
Site Selection
Always the first topic discussed when planning a vineyard. The truth is that most people already have a place where they want to grow vines. The perfect site will make great wine, but most home vineyards are not so suited. A little study and planning will make the best of existing circumstances.
The toughest challenge in site selection is soil drainage. Grapes don't like roots in a soaking wet condition, often referred to as "wet feet". Low spots and dense clay soils are difficult things to change on any particular site. But a property may have one area that drains better than others.
The optimal site will have full sun with limited shading from neighboring buildings and trees. Also minimize planting under the canopy range of trees that will compete for water.
The site will also need water. Not as much as an equivalent area or turf, but in a dry climate, you will need a source for irrigation. Many people also plant roses at the end of grape rows, since the site requirements are very similar.
Site Preparation
I took a soil sample to a laboratory familiar with grape growing requirements. I sent mine off to a private agricultural lab found in the phone book. I took a sample at the average depth of the grape root, about three feet down. The lab recommended a certain dose of fertilizer (potassium and nitrogen), so many inches of sawdust (organics for long term nitrogen) and a light dose of Borax (to increase my boron content). This was all mixed into the top twelve inches of soil with a rented skiploader.
A winegrower will not want to have tall grasses or other tumbleweeds competing with the vines, or limiting easy access by the caretaker. Prior to adjusting the soil, I dosed the entire area with roundup (consider a less expensive glycophosphate for large areas) several times to limit weeds. A better strategy would be to conduct this kill over several irrigated seasons to affect as many dormant seeds as possible. I spent a year following vine planting fighting back the re-population of weeds, but eventually got a handle on them.
Variety and Rootstock Selection
It is said that the best wines are from a variety grown as far north as it will survive, or vines that struggle to grow in their conditions. Since we live near the Mexican border with no plans to move North, I had to settle for a simpler philosophy. I chose something that grows well and produces excellent local wines. There are likely more winegrowers in any area than you might think. A little investigation (such as tasting) is a fun way to save future disappointment.
Wine grapes are succeptible to many root related diseases. For this reason, varieties with good fruit is typically grafted onto a root from a disease resistant variety. Rootstock selection may be governed by soil conditions, fertility, diseases in the geographical area and compatibility with the varietal desired. Nurseries specializing in grafted vines will help you understand your options. Some challenged soils will require vigorous roots to support plant life, but too much vigor will reduce wine quality. So rootstock selection is not a small decision.
My grafted rootstock came trom this outfit: http://www.vintagenurseries.com
Trellis Design
Grape vines can be grown in many configurations. Most of the commonly used arrangements consider sunlight exposure, controlling excess vigor, reasonable access for workers, structural stability against gravity, wind and thermal expansion/contraction of the associated wire.
Vine spacing varies greatly by region, style and variety, but generally every 5 to 10 feet, with enough space between rows for access by workers on foot, or perhaps large tractors. You'll want to spread the growth to catch the ripening sunlight, exposing the fruit to light for color and to limit mildews and fungus.
Over-vigorous vines can be countered by increasing the amount of foliage supported by each trunk. This can be accomplished with larger spacing, or developing the canopy into an H pattern.
A great resource for trellis design: http://viticulture.hort.iastate.edu/info/pdf/domototrellis.pdf
Irrigation Design
Most modern grape irrigation is done by drip systems. They are inexpensive, reliable and consistent in adding a known quantity of water to the ground between vines, minimizing evaporation and keeping the vine foliage dry. One-half inch lines are strung low, along the trellis, with emitters located as needed. These emitters are rated at certain flow rates, such as 1 gallon per minute.
Established vines are typically watered weekly, and in amounts to offset the water lost through the leaves during the day. Local or state weather services note sun radiation, temperatures and humidity to calculate an evapo-transpiration rate for each day. A grower can estimate his water requirements using this rate from the days of the previous week and the percent of shaded area on the vineyard floor. Additionally, a grower can feel the temperature of the leaves toward the end of the day. The leaves should be cool to the touch if water is still evaporating from the plant. If not, consider watering soon.
The California Irrigation Management and Information System (CIMIS): http://www.cimis.water.ca.gov/cimis/frontDailyReport.do
Pruning and Growth Maintenance
In early Spring, after the last frost threat, the dormant growth from the previous season is cut back close to the cordon (in my case, the "T"). My trellis system is called "VSP" for "Vertical Shoot Positioning". On this system each vertical shoot is cut down just above the second node above the cordon, creating a "spur". These vertical spurs are spaced about every four inches along the cordon. The cut growth is untangled from the trellis wires and then composted away from the vineyard. This old growth may have mildew or fungus spores that are best removed from the area.
As the vines begin their growing season, green shoots bud and then push from the two nodes on the spurs. New growth on the trunk, or those growing downward from the cordon are rubbed off early to focus plant energy on the upward shoots. Once the shoots are about two feet high, the healthiest of each pair is saved and the other removed. The remaining shoots are then guided up the trellis to maintain vertical position between the guide wires. Being held in a tight, vertical position offers good sun exposure for both the leaves and the fruit.
Once the shoots have established solid growth, one or two of the lower nodes on the new shoots will produce a flower cluster, which will then turn to little green BB's of fruit. The fruit will grow in size, and at the right time, begin turning to a red color. This moment is called "verasion". Once the clusters of fruit in the vineyard are almost entirely red, clusters that are greener than the norm are cut off. It would be difficult to determine unripe clusters once they are entirely red, and wine is best made from fruit of full, uniform ripeness.
Additionally, we limit each shoot to one cluster of fruit. This assures that each shoot will catch enough of the sun's energy to ripen the amount of fruit below.
This loss of fruit is heart-breaking, but a standard practice at most fine vineyards. Besides, we have plenty of fruit to reach our legal production allowance.
Once verasion is complete, growth slows and the fruit is netted to keep the birds from getting our wine. This particular type of net allows continued hedging of shoots that grow to the point of drooping so low as to shade the fruit.
We also try to keep air flowing around the fruit by pulling any leaves in contact with the berries to limit mildew damage. This also helps somewhat with light contact, hoping to "tan, not burn" the fruit in the sun.
Here is a great video presentation on pruning, in three parts:
http://connect.ag.vt.edu/westover1/
http://connect.ag.vt.edu/westover2/
http://connect.ag.vt.edu/westover3/
Disease/Pest Management
Grapes are quite succeptible to disease, including mildew, fungus and in this area, bacterial Pierce's Disease, carried by insects called Glassy Winged Sharpshooters. Mildew sprays are done here every other week, including stylet oil, baking soda and even dilute milk. Commercial fungicides can be applied if needed, along with Sevin (typical rose dust) as a pesticide to discourage sharpshooters and other leaf eaters.
We also built a couple of owl boxes, which were inhabited within weeks of construction. Our gopher population was wiped out the first season, likely due to the clear view of the clean vineyard floor, offering easy hunting for owls and hawks. We do have a weasel burrowing in the lower section, which we've only seen once while pruning. A real beautiful animal, and supposedly harmless to the vineyard.
Harvest
As the fruit ripens, the sugar content increases up towards 23 to 25 percent (units known as Brix, pronounced "bricks") of the juice content. This level will be sufficient for adequate alcohol content for taste, but not so much as to reach a toxic level that will kill the yeast before complete fermentation. The sugar levels in the fruit can be manipulated somewhat by adding or subtracting from normal irrigation.
Additionally, the seeds in the fruit are sampled to assure that the early soft green seeds turn to a hard brown color. This assures that green, or "vegetal" tastes in the wine is minimized.
Once the fruit is ripe by these two measures, the fruit is harvested in the early morning temperatures to maximize flavor.