The basic goal of grape trellising is to distribute the fruit on the vine and provide air movement and sun to the berries. In the beginning, there were head-trained vines, which involved just a stake that the vine was tied to, without wires or anything else. A great example is our Morelli Lane Vineyard Zinfandel, which dates back to the late 1800s. This was pretty much the accepted way to go until the 1960s, and still does a great job when kept well-manicured.
California sprawl arrived in the 1960s and early '70s in an effort to expand the fruit zone and get higher yields. Most of Rued Vineyard is trellised this way. Sunburn and excess vigor could be a problem with this method, so in the late '70s and early '80s, California T-trellising, with vines draped over wires like at our Mill Station vineyard, came into fashion. This allowed growers to control the canopy for more air movement and provide better shading to ease the sunburn possibility.
By the late 1990s, Vertical Shoot Positioning (VSP) became the standard for most California vineyards, as it controls the growth of the canopy for good sun and air flow, and doesn't promote rot. Open-U, or Lyre, is another style of trellising this is used in vineyards with aggressive soils or vigorous clones or rootstocks. It controls the vigor by spreading the fruit zone into two vertical curtains.