The vine is the main part of the grapevine, extending from the root system in the ground up to the cordons, or arms, of the vine. When the grape is young the trunk is very pliable and must be supported by stakes as part of a vine training system. The height of the trunk varies depending on grape variety and the type of trellis system being used and can range from 4 inches (10 cm) to 30 feet (10 m). During winter dormancy, the trunk can be vulnerable to extreme freezing conditions and will be sometimes buried and insulated with soil to protect it.
The trunk is composed of sleeves of conductive tissue, most notably the phloem and xylem. The outside bark of the vine contains the phloem tissues which transports sap, enriched by sugars and other molecules, from the leaves to the rest of the vine. During the annual growth cycle of the grapevine, the vine will start to store carbohydrate energy in the wood part of the trunk and roots. The downward passage of phloem sap to the roots and this storing process can be interrupted by the viticultural practice of "girdling" or cincturing the vine. This process can improve fruit set by forcing the vine to direct most of its energy towards developing the grape clusters. The xylem is the woody tissue on the inside of the trunk that moves sap, enriched with water, minerals and other compounds, up from the roots to the leaves.
The cordon, or "arms", of the grapevine extend from the trunk and are the part where additional arms and eventually leaves and grape clusters extend. The cordons are usually trained along wires as part of a trellis system. This training usually fixes the cordon into a permanent position, such as horizontal extending from the trunk in opposite directions.
The terms stem, stalks and shoots are sometimes used interchangeably but viticulturalists generally make some differentiation. The stem of the grapevine item, extending from cordon, is considered the shoot and this part is most often pruned in the process of "shoot thinning" to control grape yields. The stalk extending out to hold the grape cluster is known as the bunchstem while the stem of the individual grape berry is the pedicel.
The shoot of the vine develops from new buds located on the cordon and grow to include the leaves, tendrils and eventually grape clusters. Shoots first begin to the appear in spring, following bud break, accelerating growth till the flowering stage and usually slowly by the time that the vine begins veraison. During the stage of veraison (typically mid to late summer), the shoot starts to harden and change color from green to brown.